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17:30   Poster session & Welcome drinks Development of open-drive scroll expander for an Organic Rankine Cycle (ORC) engine and first test results George Kosmadakis, George Mousmoulis, Dimitris Manolakos, Ioannis Anagnostopoulos, George Papadakis, Dimitrios Papantonis Abstract: A novel open-drive scroll expander has been designed and included in a small-scale organic Rankine cycle (ORC) engine. According to the design, the heat input is 100 kWth with hot water temperature up to 100 °C and organic fluid pressure 40 bar. These conditions correspond to supercritical state of the vapour organic fluid (R-404a) with designed thermal efficiency of 6%, which is higher than similar operation at subcritical conditions. Due to supercritical operation, a new expander was necessary to be developed. An open-drive scroll expander has been designed with optimized scroll geometry, manufactured, and then integrated in an ORC engine with net capacity of 6 kW. The ORC has been installed at the laboratory for performance tests, which include the variation of heat input and hot water temperature. The tests presented here concern the first series of results for hot water temperature up to 80 °C and low expander speed (580 rpm@10 Hz), limited by severe vibrations at higher speeds. At these off-design conditions, the pump global efficiency reached was about 40%, the maximum thermal efficiency was 1.7% with expander isentropic efficiency almost 40% and volumetric efficiency about 30%, resulting to high internal leakages due to the low speed. These performance values are promising compared to part-load operation of similar set-ups, making it clear that the new expander can bring a superior performance compared to standard converted scroll expanders. Simulation of a scroll expander using R1233zd(E), R1234ze(Z) and their mixtures as drop-in replacements for R245fa Antonio Giuffrida, Davide Pezzuto Abstract: This paper presents simulations of the performance of a 2 kW hermetic scroll expander, based on a model reported in literature, when replacing the original working fluid (R245fa) with fourth-generation refrigerants. Calculations of micro organic Rankine cycles, equipped with the selected expander, show a slightly better performance when using R1234ze(Z) or R1233zd(E), as drop-in replacements of R245fa. Binary mixtures, characterized by a non-isothermal phase-change behavior, are considered too. In particular, results of mixtures depend on the fluid temperature at the expander inlet. The most relevant result is that the mixture process for some hydrofluoroolefins causes a decrease of the maximum cycle temperature, after setting a fixed expander power output, and therefore the possibility of exploiting heat sources at lower temperatures. The investigation of the recuperative Organic Rankine Cycle models for the waste heat recovery on vehicles Mingru Zhao, Gequn Shu, Hua Tian, Fengying Yan Abstract: Organic Rankine Cycle (ORC) has been valued for its promising application on the Waste Heat Recovery (WHR) from vehicles. And Recuperative ORC (RORC) is considered suitable for the on-board application because of its high efficiency. However, the previous investigations of RORC, which based on GT-suite, mainly focused on the steady state and didn’t consider the combined model with engine. In this paper, a Basic ORC (BORC) model and 3 RORC models with different recuperative rate are combined with engine model and compared. The steady state result shows that with the recuperative rate rising, the cooling heat decreases while the net output power increases, which are beneficial to the on-board application. However, the longer response time and more charged refrigerant mass are disadvantages. Also, compared with BORC, the backpressure and performance of the engine are basically not affected when recuperator is added. The transient responses show that with the recuperative rate rising, the overshoot of the temperature and output power of RORC become more serious at the start-up phase, which may cause decomposition to the refrigerant and damage to the expander. At last, the responses of combined models under varying engine condition are studied. The results show that exhaust mass flowrate is mainly responsible for the engine backpressure variation. And RORC with higher recuperative rate has more advantages under heavy-duty engine condition. Thermodynamic study of ORC at different working and peripheral conditions Talieh Rajabloo Abstract: Organic Rankine cycles (ORC) are suitable for conversion of low temperature heat to electric power. Operation of ORC is based on the same principles as that of a steam Rankine cycle, but, differs from the latter in the usage of low-boiling-point organic fluids as a working fluid [1]. Furthermore, different environmental conditions beside hot source changes affect ORC performance. Thus, off-design analysis is necessary to find performance of the cycle at various peripheral conditions. This project is conducted based on a previous study [2] in which the on-design results of ORC were obtained for pure and mixture working fluids. Besides, pool boiler was, suggested as a new approach to evaporator for the binary mixture, however, it is not the subject of this study at off-design conditions. Therefore, referring to the on-design results of low temperature ORC from previous model [2], off-design analysis of the cycle with shell and tube evaporator is conducted in ASPEN PLUS environment. The goal of this study was to provide a system design that meets the process requirements at various peripheral conditions while providing reliable operation. Results showed that higher hot source duty and heat rejection lead to better cycle performance. Moreover, a primary study on the effect of thermal decomposition of working fluid is considered in this study. To sum up, although a proper selection of mixtures of working fluid can help performance of the cycle, the heat exchanger type, peripheral conditions and properties of working fluid can, strongly, affect the performance of the ORC. Acknowledgement The author gratefully acknowledge the guidelines of professors Costante M. Invernizzi and Paolo Iora from University of Brescia, beside prof. Davide Bonalumi from polytechnic university of Milan. References 1. P. Bombarda, et al., Applied Thermal Engineering, 2009. 30: 212-219. 2. T. Rajabloo, et al., Applied Thermal Engineering, 2016. 98: 1-9. Initial design of an optical-access piston expansion chamber for wet-expansion Steven Lecompte, Martijn van den Broek, Michel De Paepe Abstract: High efficiency expanders which can cope with fluid-vapour mixtures (i.e wet expansion) at the inlet and during expansion have the potential to increase the power output from thermodynamic power cycles. Volumetric expanders are considered suitable, yet experimental results are scarce and there is no model that can predict the performance of the expansion process. This is mainly due to the knowledge gap on the fundamental aspects off two-phase expansion and the non-equilibrium effects. Therefore, in this work, a variable volume piston expansion chamber is designed. The influence of the main design parameters are investigated by means of a simple deterministic model. Based on initial figures of merit, the component selection and technical layout is presented. The optical access in a later stage will be crucial to allow investigating the mechanistic process of the nucleation and the interfacial effects. This understanding is essential for generalization of the results to other working fluids and geometries. Numerical predicting the dynamic behavior of heat exchangers for small-scale Organic Rankine Cycle Liuchen Liu, Yu Pan, Tong Zhu, Naiping Gao Abstract: Organic Rankine Cycle (ORC) system is the most widely used technique for low-grade waste heat recovery. Its two main advantages are the simplicity and the availability of its components. A typical ORC is formed by assembling heat exchangers (i.e. evaporator, condenser), flow inducing unit (pump), and power extraction unit (expander). ORC’s steady state behavior has been studied by many researchers since more than 20 years ago. Recently, developing dynamic ORC models played an increasingly important part in the system performance prediction. From the point of view of dynamic simulation, critical components of an ORC system are the heat exchangers since they are the principal media of heat transfer in and out of the unit respectively. And dynamic models for the turbo-machines (pump and expander) are avoided due to their negligible heat transfer irreversibility compared to their mechanical interaction and their relative faster response time to the heat exchangers. In this paper, moving boundary model and discretized model are used for describing the two-phase flow model of the heat exchangers. The moving boundary (MB) models are low order lumped models particular useful for optimization and control purposes. In this model, the inside part is divided into three parts: sub-cooled liquid region, two phase region and superheated vapour region. On the other side, discretized models based on the balance equations of mass, momentum and energy form an alternative to MB-models when the spatial changes are important. An advantage using discretized models is the possibility of using high accuracy correlations for heat transfer and pressure loss taking the spatial variations into account. To perform a detailed and realistic design, two concrete configurations of shell-and-tube heat exchanger (condenser) and tube-fin heat exchanger (evaporator) are taken into account. Moreover, steady-state model is established for the expander and working fluid pump. The simulation results of the established model must be compared to each other and are used to find the optimal operating parameters that maximize the waste heat recovery efficiency in response to variations of the boundary conditions such as ambient temperatures and waste heat source temperatures. DETERMINING THE INFLUENCE CHARACTERISTICS ON HEAT TRANSFER TO SUPERCRITICAL FLUIDS UNDER ORC’S CONDITIONS Marija Lazova, Alihan Kaya, Michel De Paepe Abstract: Utilisation of a low-grade temperature heat from various sources for electricity production is a reality today and is possible with an organic Rankine cycle (ORC). Even though this technology has advanced in the recent years there is still place for improvements. The main focus of this study is based on improving the efficiency of an ORC by ensuring supercritical heat transfer in the heat exchanger. The advantage of working with supercritical heat exchanger is the possibility of having a better thermal match between the heat source and the working fluid temperature profiles. In order to determine the influence characteristics on heat transfer to supercritical fluids in large diameter tubes the organic fluid R125 was selected to be tested under ORCs conditions. This working medium has favourable thermodynamic properties and low critical pressure and temperature of 36.6bar and 66°C respectively. During the measurements the heat source temperature varied between 80°C-100°C, ensuring supercritical heat transfer to the working fluid in the horizontally positioned test section with a total length of 4m. Determining the overall heat transfer coefficient was possible from the temperature and pressure measurements at the inlet/outlet of the test section and is reported in this work. Furthermore, from the measurements a new heat transfer correlation is proposed. An accurate heat transfer correlation has a strong asset and novelty by implementing them in practice for designing a heat exchanger suitable to work in supercritical regime. Field operation of a 125 kW ORC with ship engine jacket water Christopher Sellers Abstract: Improving ship system efficiency is a growing concern for the marine industry. New regulations imposed by the International Maritime Organization (IMO) have set efficiency targets for new and existing ships. These targets are outlined in the energy efficiency design index (EEDI) and will reach a maximum of 30% by 2025. In order to satisfy the regulations, ship owners are exploring new methods to improve the efficiency of existing systems. One such method is to capture and repurpose engine waste heat. Many ships employ exhaust steam boilers to recover heat from engine exhaust. This represents a source of high quality heat (≥ 200°C). At these temperatures, it is relatively easy to extract thermal energy. In contrast, low quality heat sources, such as engine jacket water (≤ 100°C), have been largely ignored. Steam production is impractical at such low temperatures. A new technology was needed to take advantage of low temperature heat sources on the ship. Calnetix Technologies, in conjunction with Mitsubishi Heavy Industries (MHI), developed an Organic Rankine Cycle (ORC) specifically designed to utilize engine jacket water as a heat source. The first prototype was successfully built, tested, and certified by Lloyd's Registry (LR) and Nippon Kaiji Kyokai (NK) in March 2015 (Yuksek 2015.) The system generates up to 125 kW from a heat source with temperature range 80°C to 95°C. This prototype was installed, commissioned, and placed into service on the Arnold Maersk container ship in April 2016. This paper will discuss difficulties which arose during the installation. It will also present and discuss data collected by the ORC's sensors during its first several months of operation. Finally benefits of the ORC operation in conjunction with auxiliary ship systems will be explained. COOLING TECHNOLOGIES FOR ORC POWER PLANTS Talieh Rajabloo, Carlo De Servi, Johan Van Bael, Robbe Salenbien Abstract: ABSTRACT With the development of binary conversion technologies, power generation from geothermal sources with temperatures down to 150°C has become technically feasible. However, a power plant working with low geothermal sources requires large volumes of water for cooling. Considering the limited water resources for human consumption and the fact that cooling water for energy production accounts for 45% of total water abstraction in European Union, new technologies in the cooling section of power plants are vital. In order to maintain large thermal outputs (>10 MW), new design strategies for the ORC cooling are necessary [1]. Overall, three types of cooling are traditionally considered for Low-T geothermal power plants; air cooled condensers (ACC), direct water cooling (WC) and mechanical-draft wet cooling towers (WCT). ACC and WCT are the most widely used [2]. Essentially, ACC can be applied everywhere, but the auxiliary power consumption is about twice as high as that for a WCT [3] resulting in 50% higher overall power plant costs. Besides, ACC perform poorly when climate is hot and humid, e.g. in summer. The collaborative project MATChING, which stands for “Materials and Technologies for performance improvement of Cooling Systems in Power Plants” funded by European Commission in the H2020 programme focusses on integration of new technologies such as new coatings based on the innovative nano-technologies, Hybrid Cooling Systems with advanced CT filling, use of alternative water sources and different cooling approaches in order to reduce water consumption in power plants. The Unit Energy Technology at VITO/EnergyVille focusses on new hybrid cooling systems for low temperature geothermal power production. Integrated design of ORC process and working fluid using PC-SAFT and Modelica Dominik Tillmanns, Christoph Gertig, Johannes Schilling, Andrej Gibelhaus, Uwe Bau, Franz Lanzerath, André Bardow Abstract: Organic Rankine Cycles (ORC) use low-temperature heat for electrical power generation. To use the full potential of a heat source, the ORC has to be tailored to the specific application. Tailoring a cycle means an integrated design of both process and working fluid. This integrated design leads to complex mixed-integer nonlinear program (MINLP) optimization problems. Today, working fluid candidates are commonly selected using heuristic guidelines; subsequently, the process is optimized for the set of preselected working fluids. However, heuristic guidelines cannot capture the strong interdependence between working fluid properties and process conditions sufficiently. Thus, the preselection can fail easily leading to suboptimal solutions. An approach for the integrated design of ORC process and working fluid is the Continuous-Molecular Targeting–Computer-aided Molecular Design (CoMT-CAMD) framework [1]. In CoMT-CAMD, the physically-based Perturbed-chain Statistical Associating Fluid Theory (PC-SAFT) equation of state [2] is used as thermodynamic model of the working fluid. In PC-SAFT, each working fluid is described by a set of pure component parameters. In a first step, the pure component parameters are relaxed during the integrated design of process and working fluid transforming the MINLP into a nonlinear program (NLP). This step is called Continuous-Molecular Targeting. The result of the CoMT step is a hypothetical optimal working fluid and the corresponding process. Real working fluids with similar properties are identified in a second step, the so-called structure-mapping. For this purpose, the objective function values of real working fluids are estimated using a second-degree Taylor approximation of the objective function around the hypothetical optimal working fluid. A Computer-aided Molecular Design formulation allows designing novel working fluids by solving the resulting mixed-integer quadratic program (MIQP). So far, the process models in CoMT-CAMD were implemented in a procedural programming language, which hinders the reusability, the use for more complex processes and dynamic simulations. In this work, we have integrated CoMT-CAMD into the object-oriented modelling language Modelica. For this purpose, Modelica is directly linked to PC-SAFT. Thereby, already existing model libraries for Modelica can be included and the programming effort for studying process variations can be decreased. The resulting design approach is applied to the integrated design of an ORC process and working fluid for a geothermal power station. Acknowledgements We thank the Deutsche Forschungsgemeinschaft (DFG) for funding this work (BA2884/4-1). References [1] Lampe, M.; Stavrou, M.; Schilling, J.; Sauer, E.; Gross, J.; Bardow, A. (2015): Computer-aided molecular design in the continuous-molecular targeting framework using group-contribution PC-SAFT. Computers & Chemical Engineering 81, pp. 278–287. [2] Gross, J.; Sadowski, G. (2001): Perturbed-Chain SAFT. An Equation of State Based on a Perturbation Theory for Chain Molecules. Ind. Eng. Chem. Res. 40 (4), pp. 1244–1260. Gear pump for low power output ORC – an efficiency analysis Zbynek Zeleny, Vaclav Vodicka, Vaclav Novotny, Jakub Mascuch Abstract: A pump is a necessary component of ORC units. Although it is simple in a principle and various pump types can be used, reality may easily bring many complications. When designing an ORC for very low power output applications (1-10 kW gross power production), problems such as leakages, mechanical and electrical losses are more significant. Using a tight and reliable pump, typically of a diaphragm type, results in extremely low efficiency, which negatively affects the overall cycle performance. We propose for micro ORC units a gear pump. Typical losses in a gear pump and their contributions with respect to issues that need to be overcome (hermetic seal requirement, reliability and overall efficiency) are described in general in the first part of this paper. The losses are volumetric, mechanical and also electrical of motor and variable frequency drive. In the second part of the paper we present the measured characteristics of the modified commercially available gear pump. The pump is intended for an ORC with a net power output of 1-10 kW. Characteristics are given for both a standalone pump and the pump coupled with an asynchronous motor. They show significantly higher efficiency than typically reported in the literature. Contribution of different losses is discussed. Mechanical losses influence operation of the pump at low pressures (lower hydraulic work but nearly constant power input) while volumetric losses at higher pressure have only small effect. The largest loss comes from electrical efficiencies of motor and variable frequency drive, especially for operation at low speed. Optimizing the operating conditions of the pump together with the motor is therefore the most important in terms of reducing pump power consumption. Numerical investigation of off-design conditions for an axial-turbo-expander in a Transcritical Organic Rankine Cycle (TRC) system Yi Chen Li, Jui Ching Hsieh, Yun Yuan Chang, Yuh-Ren Lee Abstract: The performance of a Transcritical Organic Rankine Cycle (TRC) system is affected by the heat source conditions of the exhaust gases resulting from a turbo-expander under off-design conditions. In the present study, the axial-turbo-expander of the TRC system under the design point was designed through 1-D aerodynamic theory and validated using a computational fluid dynamics (CFD) solver. The CFD solver was also used to simulate and analyze the thermal-fluid field of the turbine under various heat source conditions to determine the turbine efficiency under off-design point. The axial-turbo-expander in the TRC system, with R134a serving as the working fluid, was numerically examined to investigate the turbine performance at expander inlet temperatures of 140–115 °C and circulated loop mass flow rates of 15–12.5 kg/s. The results revealed that the isentropic efficiency of the turbine sharply dropped as the circulated loop mass flow rate increased at m ̇_w > 14.5 kg/s. However, the isentropic efficiency was only slightly affected by Tin_exp at Tin_exp > 130 ℃. In conclusion, the temperature of the circulated loop at constant mass flow rate of the circulated loop was increased to avoid performance of the expander in the low efficiency as the increasing thermal power of the exhaust gases. In contrast to the increasing thermal power of the exhaust gases, the mass flow rate of the circulated loop was decreased at the constant temperature of the circulated loop. Selected theoretical and practical investigations and optimization issues of Organic Rankine Cycle applied for waste heat use Slawomir Smolen Abstract: One of the comprehensive practical application areas of Organic Rankine Cycle is heat recovering from different low and middle temperature “waste heat” sources. The possible waste heat utilization from biogas power plants could be mentioned here as one of the typical relevant examples. Relating to this context, the paper presents some important theoretical optimization issues and selected results of the practical investigation carried out at the test and demonstration ORC plant with screw engine as expansion device. Selection of suitable organic fluids for application in Organic Rankine Cycle is a crucial step to achieve high thermal efficiency. Within a previous study a special tool has been elaborated in order to compare the influence of different working fluids on the performance of an ORC heat recovery power plant installation. The elaborated tool should create a support by choosing an optimal working fluid for special applications and become a part of a bigger optimization procedure applicable by different boundary conditions. The second optimization issue is minimization of exergy losses between heat source and the cycle by special optimization procedures selecting not only the working fluids but also evaluating the possible types of process (subcritical, overcritical, one or more stages process, internal heat recovery) under consideration of given frame conditions and limitations - mostly temperatures of the heat source and cooling air or water and pressure limitations. Based on these theoretical considerations and in accordance with practical requirement, a special ORC test and demonstration plant has been developed and installed, especially for “waste heat” utilization from exhaust gas and cooling water of biogas installations. The biggest practical solution and challenge was the application of screw engine as expansion machine. This paper presents some aspects of this, especially a novel lubrication installation adopted from a compressor and modified for the requirements of expansion machine. At the end, some representative measurement results are presented to illustrate some practical possibilities and limits of the tested installation and to compare them with theoretical assumptions. Development and applications of a 200 kW orc generator system for energy saving in chemical processes Yuh Ren Lee, Li Wei Liu, Yun Yuan Chang, Jui Ching Hsieh Abstract: Depending on heat source and heat sink conditions, an organic Rankine cycle (ORC) can be used to convert low temperature thermal energy (such as industrial waste heat, geothermal, biomass, and solar thermal energy) into electrical power. This research focuses on the development of an ORC with 200 kW power rating, which is intended to convert thermal energy into electricity for the chemical company in Taiwan. R134a is selected as the working fluid. The main components of the ORC consist of a working fluid pump, a shell-and-tube type evaporator, a shell-and-tube type super heater, a screw expander, an oil-vapor separator, and a shell-and-tube type condenser. This is the first commercially sized ORC (200 kW) operating at a low temperature (82℃) to have been successfully developed in Taiwan, with all of the components also having been manufactured in Taiwan. The test results show that the power output is 227.18 kW with a net thermal efficiency of 4.701% for a water flow based heat source at a temperatures of 82°C and at a flow rate of 189 tons per hour. Thermodynamic optimization of a double-pressure Organic Rankine Cycle driven by geothermal heat source Qingxuan Sun, Yaxiong Wang, Ziyang Cheng, Jiangfeng Wang, Pan Zhao, Yiping Dai Abstract: Geothermal energy, as a typical low-temperature heat source, has been exploited for decades to generate electricity. Organic Rankine cycle (ORC) system has a high energy conversion efficiency due to the good performance of organic fluids under the geothermal water temperature. In this study, a double-pressure organic Rankine cycle system driven by geothermal heat source is used to generate electricity. The double-pressure system achieves the cascaded utilization of energy, which can improve the efficiency of energy conversion. Mathematical model has been established based on thermodynamic laws, and the overall system performance has been evaluated. A parametric analysis is conducted to examine the effects of some key thermodynamic parameters, namely turbine high-level inlet pressure, low-level inlet pressure, high level inlet temperature, on the system performance. Parametric optimization is conducted by means of genetic algorithm (GA) to find the maximum system performance. At the same time, performances of several organic working fluids are examined. Results indicate that R245fa has a better performance among several organic fluids. The system overall exergy efficiency exceeds 5.8% under the supply water of 120°C, and it produce more than 800kW electricity with the hot water mass flow rate of 250t/h. It is also found that the turbine high level inlet pressure and low level inlet pressure has peak values on the effect of system efficiency. At the same time, the increasing turbine high level inlet temperature brings a positive effect to the system performance. Exergy analysis is also conducted and the result shows that the main exergy loss occurs in evaporator. The simulation result shows that the double-pressure organic Rankine cycle has a better performance in utilizing geothermal energy than single-pressure system. Techno-economic analysis of novel working fluid pairs for the Kalina cycle Tim Eller, Florian Heberle, Dieter Brüggemann Abstract: The organic Rankine cycle (ORC) and the Kalina cycle (KC) are well established thermodynamic concepts for decentralized power generation based on waste heat at low and medium temperature level. In a previous exergetic analysis, it has been shown that second law efficiency of KC can be increased by applying alcohol/alcohol mixtures as working fluid instead of ammonia/water. The aim of this work is to provide a detailed evaluation of operational parameters of a novel ethanol/hexanol mixture as a working fluid for the KC. Therefore, process simulations in ASPEN PLUS V8.0 are conducted. As a benchmark the KC with standard working fluid ammonia/water and the ORC are examined. Next to thermodynamic aspects, a techno-economic evaluation of the KC and the ORC is conducted. For 200 °C, 300 °C and 400 °C heat source temperature the pressure, power output, heat exchange capacity and the size parameter are analyzed. Compared to ammonia/water alcohol/alcohol mixtures offer an up to 1.5 times higher power output, an up to 66.6 % lower pressure and heat exchange capacity, but lead to 5.6 times higher size parameters. Compared to the KC, the subcritical ORC leads to an up to 3.4 % lower power output. The heat exchange capacity is at least 33.3 % and the size parameter up to 6.3 times lower. For the considered concepts, ammonia/water leads to the lowest specific cost with 619.4 €/kW. However, the cost estimation for the KC is related to several uncertainties. Therefore, the pure fluid ORC should be preferred in terms of techno-economic considerations.To sum up, the results show that the pure fluid ORC should be preferred in terms of techno-economic considerations. Design of a 1 kW Organic Rankine Cycle for teaching and research issues Christian Dirk Bonk, Christoph Laux, Maximilian Rödder, Matthias Neef Abstract: This paper deals with the design of a micro-scale ORC plant for teaching and research including the development of an automated control concept. The aim is to provide a safe and environmentally acceptable micro-scale heat engine, which can be developed, implemented and used in university labs for the education of students as well as for small research projects. The test rig allows for the support of several learning outcomes on a multi-disciplinary level particularly for the implementation and simulation of small power systems. Special attention was given to the organic working fluid characteristics and its selection process. Above performance goals, favourable safety properties and low global warming potential were decisive in the selection of the novel organic fluid called 3M™ Novec™ 649. The performance and the fluid behaviour of Novec 649 in a micro-scale power cycle is of major interest and the research goal for the test rig presented in this paper. Due to the expected power output of 1 kW a scroll expander is chosen as the generator drive for the micro plant. In order to design the major parts of the ORC, the thermodynamic simulation software EBSILON®Professional was used. Therefore the supply temperature was set to 140 °C. As a result of the simulation, feasible expander inlet pressures spread from 5.5 bar to 8.5 bar. This leads to thermal efficiencies of the ORC in the order of 5 %. Adding a recuperator to the cycle system decreases the operating pressure range but in the end the thermal efficiency can be increased by 1.5 %-points up to 6.3 %. Finally, an automated control concept is introduced, where the pump is controlled via the fill level measurement system. Integrated design of ORC process and working fluid using process flowsheeting software and PC-SAFT Johannes Schilling, Joachim Gross, André Bardow Abstract: Organic Rankine Cycles (ORCs) generate electrical power from low-temperature heat. To make best use of a heat source, ORC process and working fluid have to be optimized simultaneously. However, working fluid design and process optimization are commonly separated into a two-step approach: In a first step, promising working fluids are preselected using heuristic guidelines. In a second step, the set of preselected working fluids is employed for process optimization. However, if the preselection fails, this two-step approach leads to suboptimal solutions. To obtain an overall optimal solution, integrated design approaches have been developed.[1] However, integrated design approaches are usually complex and based on specific software and tools which prevents fast and easy development of the ORC models. In this work, we have integrated the so-called 1-stage CoMT-CAMD approach [2] into the process flowsheeting software gPROMS allowing the integrated design of process and working fluid while employing model libraries of gPROMS ProcessBuilder [3]. In 1-stage CoMT-CAMD, thermodynamic properties are modeled by the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state [4], which we use directly from the gPROMS physical property package. We have implemented the homosegmented group contribution method of PC-SAFT [5] and the Computer-aided Molecular Design (CAMD) formulation of the 1-stage CoMT-CAMD approach in gPROMS. Thereby, we can define the molecular structure of the working fluid as an additional degree of freedom within the process optimization. For this purpose, the existing model libraries of gPROMS were adapted to allow for varying molecular structures during process optimization. The resulting tool allows for easy definition and configuration of the considered process based on the “drag-and-drop” feature of the process flowsheeting software. The resulting mixed integer nonlinear program (MINLP) optimization problem is solved by the standard MINLP solver integrated in gPROMS. Thereby, the optimal working fluid and the corresponding optimal process are identified in one single optimization. We demonstrate the resulting approach for the design of a subcritical geothermal ORC application. References [1] Linke, P.; Papadopoulos, A.I.; Seferlis, P., Systematic Methods for Working Fluid Selection and the Design, Integration and Control of Organic Rankine Cycles—A Review. Energies, 2015, 8, 4755-4801. [2] Schilling, J., Lampe, M., Gross, J., and Bardow, A., 1-stage CoMT-CAMD: An approach for integrated design of ORC process and working fluid using PC-SAFT, Chem. Eng. Sci., 2016, http://dx.doi.org/10.1016/j.ces.2016.04.048. [3] Process Systems Enterprise. gPROMS. 1997-2016. Available at: www.psenterprise.com [4] Gross, J. and Sadowski, G., Perturbed-chain SAFT: An equation of state based on a perturbation theory for chain molecules. Ind. Eng. Chem. Res., 2001, 40(4):1244–60. [5] Sauer, E., Stavrou, M., Gross, J., Comparison between a homo- and a heterosegmented group contribution approach based on the perturbed-chain polar statistical associating fluid theory equation of state. Ind. Eng. Chem. Res., 2014, 53(38):14854–64. Working fluid selection and optimal power-to-weight ratio for ORC in long-haul trucks Christoph Wieland, Roberto Pili, Jesus Castro Pastrana, Alessandro Romagnoli, Hartmut Spliethoff Abstract: In 2013, about 82% of the total CO2 emissions from transportation systems in the U.S. were caused by road transportation, highly based on internal combustion engines (ICE). Organic Rankine Cycles (ORC) are a waste heat recovery (WHR) technology that can contribute significantly to reduce environmental impact of road transportation. A trade-off has to be found between the improved fuel energy utilization and the weight and volume of the ORC, which increase the vehicle load and reduce the available space for transportation. In the present work, 17 working fluids are analyzed as possible candidates for WHR with direct-evaporation ORC in long-haul trucks. The preheater/evaporator is modelled as a finned shell-and-tube heat exchanger, while the condenser is an air-cooled finned flat-tube heat exchanger, as in common truck radiators. The ORC process is optimized for each fluid in terms of maximum power output, taking into account the impact of the working fluid on the heat exchanger weight and volume. The heat exchangers are modelled in MATLAB®. The results show that acetone and ethanol can recover more than 6 kW of mechanical power, but the system would present large weight and required space. Isobutan shows the highest power-to-weight and power-to-volume ratio (234 W/kg and 277 W/dm3 resp.), but the net power output is lower. Cyclopentane and pentane allow a good trade-off between power output and space requirement. The discussed procedure can be also applied to other transportation systems, where the condenser might have to be adapted to different boundary conditions. Fluid selection and thermodynamic optimization of Organic Rankine Cycles for waste heat recovery applications Roberto Agromayor Abstract: Organic Rankine Cycles are an effective and efficient manner to convert waste thermal energy into power. One of the advantages and challenges of this kind of cycles is that the most suitable working fluid and cycle configuration have to be selected for every application. Numerous fluids can be used in Organic Rankine cycles, including hydrocarbons, HCFCs, HFCs, siloxanes, alcohols or even mixtures of fluids. The selection of the working fluid is based on many different criteria including the thermodynamic match with the heat source and sink, chemical stability, environmental concerns, safety, or cost and it is not possible to find a single best fluid for a given application. For this reason, the fluid selection and cycle optimization is usually a compromise between different factors. In this work an Organic Rankine Cycle is proposed for a waste heat recovery application where the heat source is a 10 kg/s mass flow rate of hot air at 250 oC and the heat sink is liquid water at 10 oC. 105 pure working fluids from the REFPROP library were considered and several criteria were used to screen out 71 of these fluids. A robust, steady state solver for cycles with and without regeneration was developed in MATLAB. The REFPROP libraries were linked to the solver to compute the thermodynamic properties of the working fluids. In order to select the most suitable fluids, a single objective thermodynamic optimization was performed using a genetic algorithm with the second law efficiency as objective function. The most important sources of irreversibility of the cycles were analysed and conclusions were drawn about the best fluid candidates and cycle configurations for this heat recovery application. CONSTRUCTION AND EXPERIMENTAL INVESTIGATION OF AN ORC PLANT WITH DIFFERENT WORKING FLUIDS Ebrahim Aeini, Stephan Kabelac, Xing Luo Abstract: The Organic-Rankine cycle (ORC) is a challenge for thermal scientists, as many different disciplines are involved, such as thermodynamics, cycle optimization, fluid property data, heat transfer, expansion power machinery and also model control strategies. The classical Clausius-Rankine cycles using water as a working fluid become less important on the global decarbonization road map, but the ORC is gaining importance and attention on this future development. A series of experimental and theoretical investigations are carried out at an ORC test facility at the Institute of Thermodynamics of the Leibniz University of Hanover. This test rig is designed for an electric power output of 5-10 kW powered by an electric heated thermal oil circuit of 60 kW thermal power at temperatures between 150 °C< T_input <250 °C . The facility consists of a welded heat plate exchanger use as an evaporator, a rotary piston expander, a centrifugal pump and two other heat plate exchangers, which are used as a recuperator and as a condenser. The recuperator can be selectively used or deactivated depending on the chosen operating condition. In addition, it is possible to connect a subcooler into the circuit in order to decrease the temperature of the working fluid behind the condenser. In the experimental investigations the refrigerants SES36 and Solkane R365mfc are used as a working fluid. The thermal energy is removed from the system by a water cooling circuit. The properties of the main components (heat exchanger, expander and pump) in stationary operation were modeled and compered to experimental data. Based on this stationary simulation, the feasible operating conditions and corresponding efficiencies were analyzed and discussed. The simulation show the strong influence of the recuperator on the electrical output power and the efficiency of the process. These effects were confirmed by experimental investigations, the increase of the efficiency and the electrical output power are dependent on use of recuperator. Overall, it is attempted to find an optimal operating point in which a maximum electrical output or an optimum efficiency can be achieved. The simulations have the aim of mapping the operational performance of the system by changing system parameters, for example with a change in the temperature of the waste heat flow or a change in the system pressure. The simulation was validated by means of experimental data and good correlations for both the individual apparatus involved and the overall cycle could be achieved. The contribution will introduce the test facility and will report on the experimental data gained from this device. The simulation results will be compared to the experimental data. Simulation and design tool for ORC axial turbine stage Lorenzo Talluri, Giacomo Lombardi Abstract: Axial flow turbines are the most common expanders for energy conversion. Usually axial flow turbines working fluids are air or steam; nonetheless, there is an increasing interest in evaluating this technology for Organic Rankine Cycle applications. In this field, because of the numerous possible applications, as well as the variety of specific working fluids, the selection of the turbine is usually perfected after a throughout preliminary design of the expander. Therefore, the main goal of this research is to develop a preliminary design tool for the estimation of power and efficiency of an axial turbine stage working with organic fluids. The implemented thermodynamic model applies systematically real fluid properties. Furthermore, not only a mean line analysis is available in this simulation tool, but also a Non-Isentropic Simple Radial Equilibrium (NISRE) model, in order to evaluate the thermodynamics and kinematics of the flow throughout the blade, is presented. A geometric parameterization was added to develop an optimal configuration of the channel, which can be adapted to the user requirements, to ensure maximum flexibility for different ORC applications. The methods applied, as well as various simulation results with different working fluids, from refrigerant to hydrocarbons, are presented. A world overview of the Organic Rankine Cycle market Thomas Tartiere, Marco Astolfi Abstract: The Organic Rankine Cycle (ORC) technology is a reliable way to convert heat into electricity, either for renewable energy applications (biomass, geothermal, solar), or industrial energy efficiency. ORC systems range from micro-scale (a few kW) for domestic cogeneration to large multi-megawatt geothermal power plants. After a slow initial start, the technology has experienced a much stronger development since the 1970s, mainly because of economic incentives and surging energy prices. However, the large range of applications, manufacturers, and countries make it hard to track the evolution of the technology over the world. Information about more than 700 projects has been collected, cross-validating 27 manufacturers’ data with publications and testimonies, allowing to build the first reliable and exhaustive database of ORC plants. As a result, this work analyses the evolution of the ORC market over the years, with today 2.7 GW of cumulated installed capacity. After introducing the ORC technology with a focus on its history, working principle and main applications, the current state and the new trends of the ORC market are presented with a detailed analysis of each application. The evolution of each market is discussed considering the present installed capacity, historical data and macro-economic trends. Finally, future perspectives and growth potential of the ORC market are evaluated, with a special focus on Waste Heat Recovery applications. Small Organic Rankine Cycle coupled to parabolic trough solar concentrator Uzziel Caldiño, Juan Garcia, Laura Castro, Oscar Jaramillo, Gustavo Urquiza, Franciso Flores Abstract: In this paper, the design and performance of small Organic Rankine Cycle (ORC) coupled to parabolic trough solar collector (PTC) are showed. The system is analyzed using the first and second laws of thermodynamics. This small ORC is designed to provide 10 kWe for almost 18 hours every day and also energy to heat water. The main components of this system are: a) parabolic trough solar concentrators (PTC), b) thermal storage system and c) ORC system, which uses R245fa as working fluid and a radial turbine as expander. The ORC system is designed to operate in Temixco, city located at the central region of México. The solar radiation database of Temixco was used to compute the estimated performance of the proposed ORC system. Simulation was carried out using Matlab and CoolProp. The ORC power and efficiency were computed. The mass flow and thermal load stored for the PTC loop are shown. Experimental investigation and CFD analysis of heat transfer in single phase subcooler of a small scale waste heat recovery ORC Tryfon Roumpedakis, Spyros Chapaloglou, Platon Pallis, Aris-Dimitrios Leontaritis, Konstantinos Braimakis, Sotirios Karellas, Panagiotis Vourliotis Abstract: In the present work, a detailed investigation of the single phase heat transfer mechanism in a novel subcooler of an experimental small scale waste heat recovery Organic Rankine Cycle (ORC) unit is presented. The ORC unit is operating with R134a as the working fluid and it is designed to utilize the waste heat from the jacket water of marine diesel auxiliary internal combustion engines (ICEs). The ORC unit produces 3.7 kWel net electrical power at a cycle pressure of 25 bar and a high temperature of 82oC. The application of subcooling in such systems is common practice, so as to ensure the cavitation free operation of the pump. The subcooler is designed to achieve a certain level of subcooling and minimizing at the same time the pressure losses on both the refrigerant side and the cooling water side. A theoretical CFD model is developed to predict the behavior of the respective heat exchanger. A novel heat transfer correlation is proposed for the single phase heat transfer inside a corrugated tube for the R134a, to enhance the accuracy of the model predictions and is compared with proposed from literature correlations. The results of the heat transfer model are validated by the experimental data collected from the respective ORC unit. Optimization of heat exchanger size of a 10 kW Organic Rankine Cycle system Alireza Jafari, Chien-Yuh Yang, Chi-Che Chang Abstract: Most of the heat exchanger design in a Rankine cycle power generation system is based on the assumption of a fixed temperature difference between the heat source and the inlet temperature of the expander. Since the temperature difference between the evaporator and the condenser is high, the effect of this estimated temperature difference on the system performance is negligible. However, for an ORC system, the temperature of heat source is low; any minor difference on the temperature estimation will affect the system thermal efficiency significantly. This study provides an experimental and analytical study of a practical 10 kW organic Rankine cycle system using HFC-245fa as working fluid subject to the influence of heat exchangers with different NTU. The effect of NTU of evaporator on heat transfer rate, network output, system thermal efficiency and investment payback years were studied. The results show that with increasing NTU of evaporator leads to the increase of total heat transfer rate, work output and system thermal efficiency. However, since the system installation cost increases with increasing heat exchangers NTU, in combining with the increase of power output, an optimal heat exchanger NTU for the shortest investment payback years can be found. Radial expander design for an engine Organic Rankine Cycle waste heat recovery system Fuhaid Alshammari, Apostolos Karvountzis-Kontakiotis, Apostolos Pesiridis, Timothy Minton Abstract: It is commonly accepted that waste heat recovery technologies are significant contenders in future powertrain thermal management to further minimize fuel consumption and CO2 emissions. Organic Rankine Cycle (ORC) systems are currently regarded as amongst the most potent candidates in recovering a engine exhaust energy and converting it to electrical power. Crucial areas for the maximization of the efficiency of the ORC system are the appropriate selection of working fluid and the optimization of the expander design. In this study, a novel design methodology of a radial turbine expander for a heavy duty engine ORC waste heat recovery system is presented. The preliminary design of the radial turbine expander includes the development and utilization of an in-house 0/1D code that can be coupled with various organic fluids properties for the calculation of the basic expander geometry. The initial mean-line model for a 200kW-class Diesel engine application investigated produced a solution for a 20kW turbine with 73% isentropic efficiency. The preliminarily optimized expander geometry was used as an input in a detailed CFD code to further optimize rotor geometry. The rotor geometric optimization showed that by increasing exit tip radius by 10% and adopting a 50o back-swept blade design, the maximum isentropic efficiency achieved can exceed 83%. Exploration and Analysis of CO2 + Hydrocarbons Mixtures as Working Fluids for Trans-critical ORC Lejun Feng, Danxing Zheng, Jing Chen, Xiaoye Dai, Lin Shi Abstract: ORCs (Organic Rankine Cycles) are of great significance for energy conservation and CO2 emission reductions owing to their usage in converting low grade waste heat to electrical power. The working fluid properties are the key to getting good cycle performance. The advantages of CO2 and hydrocarbon working fluids for use in ORCs are investigated here for six binary mixtures: CO2+propane/n-butane/iso-butane/n-pentane/iso-pentane/neo-pentane. A transcritical ORC simulation program was used to predict the cycle performance for various hydrocarbon mass fraction working fluids for a turbine inlet temperature of 453.15 K and inlet pressure of 1.3pc. The predicted cycle performance is used to divide the six working fluids into three categories relative to the thermal efficiency of an ORC using pure CO2. The first working fluid type (CO2+propane) has increasing efficiencies with increasing hydrocarbon mass fraction while the second type have maximum thermal efficiencies at hydrocarbon mass fractions of 0.3, and the third type has maximums at a mass fraction of 0.2. In addition, the thermodynamics relative efficiency,  , is highest for CO2+propane and then decreases for CO2+iso-butane, CO2+ n-butane, CO2+neo-pentane, CO2+iso-pentane, and CO2+n-pentane with the lowest. Then, the cycle efficiencies of the three working fluid types were analyzed from the perspective of the hydrocarbon molecular structure. The results show that longer main carbon chains and branched carbon chains have larger pc and Tc, with this critical property leading to higher efficiencies at low hydrocarbon mass fractions. Lower pc and Tc lead to higher efficiencies at high hydrocarbon concentrations. Thus, there is a trade-off between the cycle efficiency and the hydrocarbon mass fraction. Finally, the three best working fluid mixtures, 0.3CO2/0.7propane, 0.7CO2/0.3neo-pentane and 0.8CO2/0.2pentane, were further analyzed according to their cycle characteristics. The 0.3CO2/0.7propane mixture working fluid had the best cycle efficiency for these conditions. Keywords: transcritical ORC; hydrocarbons+ CO2; thermal efficiency; thermodynamics consummating degree; mass fraction Study on applicability of radial-outflow turbine type for 3 MW WHR Organic Rankine Cycle Dmytro Maksiuta, Leonid Moroz, Maksym Burlaka, Yurii Govoruschenko Abstract: The article presents the results of study on the reasonability of using radial-outflow turbines in ORC. Peculiarities of radial-outflow turbine design utilizing modern design technologies and application to ORC was considered in the first part of the paper. The second part of the paper describes the selection process of the best turbine type for 3 MW WHR ORC power unit for internal combustion engine. The selection was performed among different turbine types, like radial-inflow, axial and radial-outflow turbines which were designed with given boundary conditions. The advantages and disadvantages of their application were shown. Eventually, the recommendations regarding application of different turbine types for 3 MW WHR Organic Rankine Cycle were given. Performance improvement of distributed combined cycle plants through modification of structure Jacek Kalina Abstract: Current trends in design of combined cycle power only and cogeneration plants show that developers increase plant size and complexity of the system in order to reach high power generation efficiency at acceptable specific investment cost. On the other hand national energy systems face challenges related to the use of energy from intermittent renewable energy sources. Flexibility of the system is becoming an important issue and criterion for design of energy conversion plants. In this context the distributed small and medium scale modular combined cycle plants can be an interesting alternative. Traditional combined cycle power plant consists of an industrial gas turbine, a heat recovery steam generator and a steam turbine cycle. In the case of small and medium scale plants the power generation efficiency is within the range of 42 – 47%. If supplementary firing of natural gas is applied for higher power output the efficiency is even lower. Some authors proposed bottoming of the traditional combined cycle plants with additional ORC modules. In this paper possible modifications of an entire plant structure are examined. The concept is based on a bigger number of power generation modules and modified configuration of the heat recovery steam generator to be used. Components such as internal combustion engines, turboexpanders, inverted Bryton cycle and ORC are taken into account. There are also being considered different types of gas turbines such as aeroderivative, recuperated and reheated ones. Simulations were performed using Engineering Equation Solver and Ebsilon Professional software packages. Results show that there is a room for both efficiency and flexibility improvements. Organic Rankine Cycle with relatively high working fluid evaporation temperature can play an important role in these new combined cycle plant configurations. Closed loop organic wind tunnel (CLOWT): design, components and control system Felix Reinker, Eugeny Y. Kenig, Max Passmann, Stefan aus der Wiesche Abstract: Organic Rankine Cycle (ORC) systems offer a suitable technique to achieve reduced energy consumption. However, experimental work is largely lacking, and there is an overweight in theoretical work. For this reason, the computation of dense gas flows still represents a major difficulty in ORC development, and there is a need for validation studies based on experimental data, which is currently hardly available. The Closed Loop Organic Wind Tunnel (CLOWT), is a facility to fill this gap. In the first part of this contribution, the design of the CLOWT is presented. A close look will be taken at the main components, such as compressor (especially shaft sealing) and chiller. Furthermore, typical wind tunnel components, such as diffuser, settling chamber, and nozzle, are briefly discussed. Based on the test rig design, the second part shows the basic operating principle of this closed gas cycle, focusing on an exemplary thermodynamic cycle at maximum compressor power. The third part deals with the control system of the CLOWT. For a closed wind tunnel, the setting of the operation points for testing requires special attention, and some similarity to closed cycle gas turbine systems exists. However, in case of a closed wind tunnel, inventory backward control approach is difficult to realize directly. To overcome this problem, an inventory forward control approach is designed for the CLOWT. The findings presented in this part are used to build up a distributed control system. THERMOECONOMIC ANALYSIS OF ORGANIC RANKINE CYCLE BASED ON DIFFERENT ECONOMIC INDICATORS Xinxin Zhang, Xiaoyu Yang, Jingfu Wang Abstract: The organic Rankine cycle(ORC) is a popular technology used in waste heat recovery and low-grade heat utilization. However, the application of ORC is subject to limitation on some occasions due to its high investment cost. In this paper, the ORC used for recovering the waste heat of flue gas was studied and cost model of ORC was established with detailed calculation. Two organic working fluids, R123 and R245fa, were selected for conducting the analysis. Five economic indicators, including average investment of the system, annual net earning, dynamic payback period, return on investment, and power generation cost, were used as the basis for analyzing the variation effect of the flue gas inlet temperature, evaporation temperature, and condensation temperature on the above five economic indicators. The study found that among all these five indicators, R245fa has four prevailing indicators while R123 has only one. Therefore, R245fa can be a good working fluid. Optimization of an Organic Rankine Cycle as bottoming cycle of a 1 kWe genset for residential applications Alejandro Lavernia, Davide Ziviani, Bryce Schaffer, Kunal Bansal, Eckhard Groll Abstract: A novel 1 kWe GENSET featuring an internal combustion engine (ICE) operating on Spark-Assisted Compression Ignition (SACI) combustion of natural gas is under development to achieve an overall power generation efficiency of 40%. The aim is to create an efficient electricity generation system that can provide the energy necessary for light residential use at high thermal efficiency and low user cost. In order to achieve such power generation efficiency for a small-scale energy/heat production unit, an organic Rankine cycle (ORC) has been proposed as a bottoming cycle to recover heat from the exhaust of the small internal combustion engine. The ORC has been optimized to operate with a heat source inlet temperature of 400 ºC, which is necessary for use with the integrated catalytic converter evaporator proposed for the system. By means of a thermodynamic cycle model, the final cycle architecture has been identified along with the design of a novel two-stage scroll expander integrated with working fluid pump. Results showed that by employing R1233zd(E) as the working fluid, the theoretical cycle efficiency is as high as 15.8% with a net power output of 176.2 W. Modeling of brazed plate heat exchangers for ORC systems Vijaya Sekhar Gullapalli Abstract: The design of efficient ORC systems involves selection of thermodynamic cycles and working fluids, optimization of operating variables and selection of components for available heat sources. These optimization processes involve determining heat exchanger performance and selection calculations suitable for various cycles and dealing with multiple heat sources. The current article presents a steady state ORC system simulation tool in which the main emphasis is given to braze plate heat exchanger (BPHE) modeling and selection. A unique 1D pressure-enthalpy based discretized method is developed for the simulation of heat exchanger components. The developed method is generic and can be adopted for simulating single phase, super-critical, evaporation and condensation processes with full or partial phase change. To improve the stability and speed of fluid property retrieval, a bilinear finite grid interpolation method based on property maps obtained from standard libraries such as NIST REFPROP and COOLPROP is developed. An Organic Rankine Cycle for two different heat sources: Steam and hot water Taehong Sung, Kyung Chun Kim Abstract: Direct use of a steam heat source for the organic Rankine cycle system is one of the key challenges in various plant industries where low-grade steam is available and is becoming difficult as the parent system has a strong variability. In addition, changing the type of the heat source fluid among steam, hot water, thermal oil and others from the parent plant could increase the operation time of the heat recovery system, which increases system economics and makes it more attractive. Although a variety of ORC systems have been developed mainly using single heat source as hot water heat source or a heat transfer loop. An ORC system with the direct use of a steam heat source has been rarely reported, and a system using two different heat sources have not been reported yet. Here we evaluate the performance characteristics of an ORC system using two different heat source fluids: steam and hot water. The target ORC system was originally developed for the hot water heat source and has a simple cycle configuration with R245fa as working fluid, and is composed of typical four components as: a two-stage radial turbine and a coupled generator, plate-type heat exchangers with a refrigerant tank, and a multi-stage centrifugal pump. The nominal net power output at the design point is 187.9 kW with the turbine expansion ratio of 9.5. The heat exchanger analysis showed that the steam heat source can be applied to this system. The isothermal heat exchange and high heat transfer coefficient at the two-phase region of the steam showed a large overdesign for the current application. We tested the ORC system using a steam generated from an incineration plant. The temperature and pressure of the steam were 143.5℃ and 302 kPa. We showed that the ORC system originally developed for the hot water heat source could be used for the steam heat source without any major system changes. Thermal performance of brazed metalfoam-plate heat exchanger as an evaporator for Organic Rankine Cycle Dae Yeon Kim, Kyung Chun Kim Abstract: Compact-sized organic Rankine cycle (ORC) power generators call for higher performance and down-sized heat exchangers. Since heat exchangers in ORC systems, especially evaporators contribute to a big portion of the system size as well as the capital cost, and their price is also directly related to their size. Since the heat transfer area plays a direct role in the performance of heat exchangers, microcellular structures such as metal foams are proposed to increase the heat duty of heat exchangers by increasing the surface area while maintaining their volume. High-porosity metal foams are proposed for insertion into heat exchanger channels to enhance the heat transfer mechanism in evaporators. Their high surface area to volume ratio makes them a good candidate for manufacturing high-performance heat exchangers. The metal foams are being considered to improve performance while keeping the size of heat exchangers small. In this experimental study, the performance of a 100 kW class heat exchanger with the channels brazed with nickel based metal foam and stainless steel sheets was investigated. A hot water loop was designed for heat input. The cold side of the heat exchanger works with R245fa as the working fluid. The phase-change heat transfer experiments were performed with different mass flow rates ranging from 0.32 to 0.61 kg/s while the operating pressure was at 10 to 14 bar with hot water inlet temperature was 133°C. Furthermore, the heat transfer performance was compared with the commercial plate heat exchanger (produced by Alfalaval, AC120EQ) which was custom-made as a 100kW class evaporator. In the comparison test, refrigerant side has 0.6 kg/s of mass flow rate at 40°C and heat source side has 1.2 kg/s mass flow rate at 130°C. Although the pressure drop in the metal foam plate heat exchanger is increased compared to that of the conventional plate heat exchanger, increase of the recovered waste heat from the heat source is much higher due to higher overall heat transfer coefficient. As a result, the energy density of the new heat exchanger is about 2.5 times higher than that of the conventional plate heat exchanger. Converting a commercial scroll compressor into an expander: Experimental analysis and analytical performance evaluation Maurizio Cambi, Roberto Tascioni, Luca Cioccolanti, Enrico Bocci Abstract: The core of the work is split in two parts, the first one regards an experimental analysis on a micro Organic Rankine Cycle lead to extrapolate the real compressor and turbine efficiency, then, in the second part of the work such data have been utilized as input to a mathematical model. The experimental test founded by a HVAC company is based on a scroll compressor modified to work as scroll expander, a not regenerative cycle, a subcritical fluid regime, aimed at reducing in system cost and complexity. The scroll expander has been tested with its fluid R 410 in a real ORC cycle in order to get the isentropic efficiency of the scroll expander (0.5) and the pump (0.4). On the basis of the experimental tests, a model accomplished by means of REFPROP has been carried out to evaluate the performance of the ORC group to achieve 10 kWe as target power output. Four operative fluids have been simulated, i.e. R 245fa, R 134a, R 1234yf, R 1234ze, fixing 100 °C as overheating temperature and considering condenser temperature in the range 20°-50°C. The results have showed that 245fa is the most promising working fluid since it gives an higher expansion ratio within lower pressure values, as a consequence not only a lower mass flow rate is necessary but overall a lower pump consumption is needed, reaching greater overall conversion efficiency (about 6% with condensing temperature of 20°C). Thus, a commercial heat pump scroll compressor can be effectively converted into an expander. The first fluid selection shows that the most used ORC fluid can be used within relative low performance but surely, low cost and easy management. A mean-line model to predict the design efficiency of radial inflow turbines in Organic Rankine Cycle (ORC) systems Luca Da Lio, Giovanni Manente, Andrea Lazzaretto Abstract: The favorable thermodynamic properties of an organic fluid make the Organic Rankine Cycle (ORC) systems the best option for power generation from low-to-medium temperature heat sources due to the lower heat transfer irreversibilities and higher efficiencies compared to steam power systems. The lack of extensive experimental data on the efficiency of turbines operating with high molecular weight fluids makes turbine design a very challenging task. In particular, a low enthalpy drop, large volume flow ratios per expansion stage and low speed of sound represent very different flow conditions from those generally experienced by steam or air. In this paper the preliminary results obtained by a 1D model of single stage radial inflow turbines operating with R245fa are presented. The model takes into account the real gas properties and is organized into two main consecutive steps: the “preliminary design” (PD) and the “performance analysis” (PA). In the former a first turbine geometry is defined starting from the cycle design specifications and non-dimensional parameters (velocity ratio and specific speed). In the latter the turbine efficiency is calculated using the loss correlations specifically developed by Aungier (2005) for radial inflow turbines or adapted from the centrifugal compressor field. As the preliminary design requires first attenpt values for the efficiency and the total rotor inlet pressure, several cascaded PDs-PAs are needed until convergence. The first runs of the model at different cycle design specifications and non-dimensional parameters already provide a clear indication of their influence on the efficiency of single stage radial inflow turbines for ORC systems. EXPERIMENTAL ANALYSIS OF AN ORGANIC RANKINE CYCLE FOR A COMBINED HEAT AND POWER SOLAR BIOMASS SUPPORTED APPLICATION Joaquín Navarro-Esbrí, Francisco Molés, Bernardo Peris, Roberto Collado, Manuel González, José Pascual Martí Abstract: Due to environmental constrains, Combined Heat and Power (CHP) systems and bottoming power cycles for waste and revewable heat valorization have received considerable attention over the past decades. Among the several proposed power cycles, the Organic Rankine Cycle (ORC) has been attracting increasing attention, having proved as a feasible technology for low temperature and small scale applications. The aim of this work is to present an experimental analysis of an ORC, suitable for a CHP application for buildings that uses solar biomass supported renewable energy as heat source. Fristly the design data of the ORC module, including working fluid and configuration selection, from the technical requirements of the equipment imposed by the application is exposed, where the operating conditions have been selected in order to maximize the efficiency of the system. Finally, the obtained ORC prototype is experimentally characterized. The experimental results have been used in order to predict the expected behavior of the ORC module in the final application and the performance of the cogeneration system is summarized. Overview of the activities on heavy duty diesel engines waste heat recovery with Organic Rankine Cycles (ORC) in the frame of the ECCO-MATE EU fp7 project Simone Lion, Ioannis Vlaskos, Cedric Rouaud, Rodolfo Taccani Abstract: The ECCO-MATE Project is a European Union funded project aimed to develop a synergistic framework for cutting edge research on novel engine technologies for higher energy efficiency and lower emissions. The project partners, Ricardo, an engineering consulting company, and the University of Trieste, focus the research attention on waste heat recovery systems, such as Organic Rankine Cycles (ORC), which are gaining increasing interest by engine manufacturers, vehicles and ships fleet operators, because of their potential for further increasing engine efficiency and decreasing fuel consumption. In particular, in the frame of the developed research activity, the 1-D Ricardo proprietary engine simulation software WAVE has been used in order to assess novel engine concepts, both in the commercial vehicles and marine sectors. A combined engine-ORC system First and Second Law of Thermodynamics analysis has been proposed in order to study where system inefficiencies are concentrated and propose improvements, with particular focus on commercial vehicle heavy duty diesel engines. A thermo-economic analysis has been also considered. In collaboration with the project partners National Technical University of Athens (NTUA) and Winterthur Gas & Diesel, an innovative low pressure Exhaust Gas Recirculation (EGR) configuration for low speed 2-stroke ship propulsion units has also been studied with the aim of reducing NOx in order to meet IMO Tier III emissions limits. ORC systems are, in this application also, a promising technology that can be used, in synergy with emission reduction systems, to recover, in particular, low temperature heat sources such as engine coolant and scavenging air, always with the aim of improving overall system efficiency while respecting new stringent emission reduction targets. The first results of the research activity show that a fuel consumption improvement up to 10% could be achieved both for commercial vehicles off-highway applications and in the marine sector, depending on the type of ORC architecture chosen. Operation and maintenance of a biomass fired – Organic Rankine Cycle – CHP plant: the experience of Cremona Andrea Salogni, Davide Alberti, Massimo Metelli, Roberto Bertanzi Abstract: Thanks to various feed-in-tariff programs, aimed to the development of the renewable energy production, several biomass firing power plants had been realized in Italy in the last few years, contributing to the reduction of greenhouse gas emissions and fossil fuel energy dependence. In particular, during 2012 there was a rush for the completion of several renewable energy conversion power plant, leading up to 986 new plants to get the first connection to the grid (+81,3% with respect to 2011); among those, 80 new plants were solid biomass firing plants (+47,1% with respect to 2011). Linea Energia S.p.A., the Energy Business Unit of the multiutility company LGH, Linea Group Holding, which operates over the area of Brescia, Cremona, Crema, Lodi and Pavia, gave its contribution in 2012 with the realization and start-up of two waste wood fuelled energy conversion plants located in the Northern Italy, more exactly in Cremona and around Brescia. This paper focuses on the operation and maintenance experience of the waste wood conversion power plant of Cremona, which is capable for a gross electric power production of up to 1.0 MW and a thermal power recovery of up to 5.5 MW. In the first part of this paper, a detailed description of the plant is presented, giving an insight of the engineered process. In the second part, the performance analysis of the energy conversion process is discussed by comparing actual performance of the system with the originally defined reference performance. As a consequence of the operation of the unit in anomalous conditions (air entering in the system) the output of the turbine decreased but was then successfully re-established after an extraordinary maintenance carried out by the turbine supplier. Application and operational experience of 40+ Triogen ORC plants Quirijn Eppinga, Stefano Ganassin, Jos van Buijtenen Abstract: The high temperature ORC of Triogen was originally designed to utilize exhaust heat from landfill gas engines. Now more than 40 plants are operational, it is worthwhile to have a look at the different applications, and how lessons learned can lead to a new design. Giving the working fluid and the design of the evaporator, heat source temperature may vary between 350 and 530 °C. At the heat rejection side, sometimes a useful heat sink other than the ambient may be utilized at a higher temperature, of course penalizing power and efficiency. The various heat sources and the condenser conditions applied will be described. Engines fuelled by various fuels from bio-oil from pig fat to gas from landfills, mines and digesters were seen as heat source, but also flue gas from the combustion of various kinds of biomass. All these led to a variety of heat source temperatures and flue gas compositions, where problems like slagging, fouling or abrasive wear of evaporator surfaces had to be met. Various schemes in terms of number of engines feeding one or more ORC plants were build. Condenser heat was sometimes used for heating or drying purposes. Each situation required a specific solution for applying the mostly standard ORC plant. These solutions involved the flue gas systems (including provisions for metering flue gas flows), evaporators and heat rejection systems. Within the standard ORC module, the only variable is the turbine nozzle, for optimization of performance pending heat input and back-pressure based on condenser condition. This paper will describe how optimal solutions were arrived at. An overview will be given of installed plants, mentioning their specific demands and how these were met. Special emphasis will be given at cases with high condenser conditions, where the ORC is being utilized as combined heat and power unit. Operational experience will be reported on in terms of availability, and how the current level of availability was arrived at by careful following the learning curve. Finally a new concept plant design will be presented, which takes care of all lessons learned. Thermodynamic analysis of a small scale combined cycle for energy generation from carbon neutral biomass Riccardo Amirante, Pietro De Palma, Elia Distaso, Antonio Pantaleo, Paolo Tamburrano Abstract: The aim of this paper is to investigate the thermodynamic performances of a small-scale power plant employing a combined cycle for the generation of useful energy from carbon-neutral biomass, such as pruning residues. The combined cycle has the particularity of being composed of a cost-effective topping plant based on a Joule Brayton cycle, which is achieved by using a cheap turbocharger from the automotive industry instead of a more expensive commercial micro-turbine. The turbocharger can be either directly connected to the electric generator (after a few modifications) or coupled (without modifications) with a power turbine moving the generator. The use of solid biomass as fuel is allowed by coupling the turbocharger with an external combustor and a gas to gas heat exchanger. The warm flue gases exhausted by the topping cycle are then used in the bottoming cycle to produce steam, which can power a steam expander. This paper thermodynamically assesses this combined cycle in the case of using the turbocharger plus the power turbine; a very small scale configuration (50 kWe) with a fully electrical energy generation arrangement is considered in the analysis. Furthermore, the main aim is to compare the bottoming Rankine cycle with a bottoming ORC in terms of overall efficiency and sustainability. Selection criteria of optimal separation pressure of liquid dominated geothermal resources Marco Snaidero, Federico Minoli, Marco Frassinetti Abstract: The purpose of this paper is to define the main selection criteria of the separation pressure for geothermal binary power plants to maximize the efficiency of the system. Separation pressure is one of the main parameters that defines temperature, flow and brine/steam ratio of the geothermal resource and thus it is a key point for its proper exploitation. Considering the specific constraints of each resource, it should be optimized to ensure the maximum power production with a proper cycle design. On typical resources for binary plants, an analysis has been performed to evaluate the effect of different separation pressure on cycle selection. Following, a simulation of the off design conditions of the ORC has been performed to understand the behavior of the overall system varying the separation pressure, in order to obtain a set of data useful for the cycle assessment of geothermal projects. Multi criteria optimization of plate heat exchangers for super critical C02 power systems Gianluca Lillo, Rita Mastrullo, Alfonso William Mauro, Luca Viscito Abstract: Supecritical CO2 power systems are an interesting option to allow the use of low grade thermal sources, especially for small size plants where compactness and costs are of primary importance in order to spread their use and innovative high pressure plate heat exchangers could be used. In this paper a detailed heat transfer model and an analysis related to the optimization of a water-to-CO2 supercritical plate heat exchanger is presented according to the criteria of size minimization and thermal-hydraulic performance enhancement. The assessment based on different plate exchanger geometric configurations is presented to allow design optimization. A NEW TEST STAND FOR INVESTIGATIONS OF ORC-EXPANDERS - EVAPORATION BEHAVIOR OF ETHANOL AND ETHANOL-WATER MIXTURES Martin K. Günzel, Roland R. Scharf Abstract: Organic-Rankine-Cycle- (ORC-) technology is considered as an additional system to improve the energy efficiency of combustion engines. The concept is to use the hot exhaust gases to evaporate the ORC-fluid. Other than, for stationary utilization the ORC-technology has not been scaled down to mobile uses, such as in trucks, coaches, trains and or other mobile work machines, yet. In these applications, new challenges arise, due to variations in the load profile of the engine. For safe operation, turbinetype expanders require well defined working fluid parameters for the superheated steam. Decreasing engine load and related lower exhaust gas flow requires adjusted mass flow-rates in the ORC. In this study the evaporation behavior of ethanol and ethanol-water mixtures was investigated in a standard finned tube evaporator. The mass flow was gradually reduced from the design point at various constant steam parameters. The inlet temperature of the exhaust gas was maintained constant. The exhaust gas flow was varied until the evaporation including overheating of the ethanol or ethanol-water mixture were stable. The influence of the heat transferability as a function of exhaust mass flow and steam mass flow as well will be discussed. In addition, a comparison is made between undenatured ethanol and ethanol denatured with methylethylketone (MEK). Furthermore the thermal decomposition of the investigated working fluids has been monitored during the tests. Temperature control of evaporators in automotive waste heat recovery systems Michiel Oom, Emanuel Feru, Bram de Jager, Henk Ouwerkerk, Rick de Lange Abstract: This paper presents a control strategy for the steam generation process in automotive waste heat recovery systems that are based on the subcritical Rankine cycle. The central question is how to regulate the flow of water into the evaporator such that dry steam is generated at its outlet, subject to large variations in the heat input. Tight control of this process increases the amount of recovered energy while ensuring safe system operation. The method consists of inversion-based feedforward combined with output feedback on the temperature of the evaporator, which is estimated using exhaust gas measurements. As this method does not require a high fidelity evaporator model, it is easy to implement. It is demonstrated on an experimental setup, where the exhaust flow is imitated by electrically heated air. On an automotive driving cycle, steam was generated reliably with a superheating temperature of 10-20 [K]. Design and commissioning of a thermal stability test-rig for mixtures as working fluids for ORC applications Luuc Keulen, Chiara Landolina, Andrea Spinelli, Paolo Iora, Costante Invernizzi, Luca Lietti, Alberto Guardone Abstract: A novel test-rig for studying the thermal stability of mixtures as working fluids for ORC applications was designed and commissioned at the Laboratory of Compressible-fluid dynamics for Renewable Energy Applications (CREA) of Politecnico di Milano, in collaboration with the University of Brescia. The set-up is a standard one, in which a vessel containing the fluid under scrutiny is placed in a vertical oven for ~ 100 hours at a constant temperature T=T^. During the test, the pressure P is monitored to detect thermal decomposition of the fluid. For P < 10 bar, pressure sensor T2 is used (Full Scale 10 bar, FS, expanded uncertainty 0.05% FS or +/-5 mbar), for P > 10 bar , pressure sensor T3 is used (FS 35 bar, expanded uncertainty 0.05% FS or +/- 17.5 mbar). After the test, the vessel is placed in a controlled thermal bath (with accuracy +/- 0.1°C), where the pressure is measured using transducer T1 (FS 1 bar, expanded uncertainty 0.05% FS or +/- 0.5 mbar) at different value of the temperature T, with T < T^ and T < Tc (Tc critical temperature). The resulting isochoric pressure-temperature dependence is compared to that obtained before the fluid underwent thermal stress. If departure from the initial fluid behaviour is observed, significant thermal decomposition occurred and a chemical analysis of the decomposition products is carried out using gas chromatography and mass spectroscopy. The novelty of the set-up is the possibility of taking samples of both liquid and vapour phases of the fluid, a capability that was introduced to study thermal decomposition of mixtures, whose composition depends on the pressure and temperature, as well as to capture the more volatile products of thermal decomposition of pure fluids and mixtures. Preliminary experimental results are reported for the pure siloxane fluids MM (Hexamethyldisiloxane, C6H18OSi2) and MDM (Octamethyltrisiloxane, C8H24O2Si3) and MM-MDM binary mixtures. An analysis of fast-response pressure probes dynamics for ORC power systems Pietro Molesini, Giiulio Gori, Alberto Guardone Abstract: The dynamic response of line-cavity systems in ideal and non-ideal compressible-fluid conditions is investigated numerically using the SU2 open-source suite for multi-physics simulations. The response of the system is studied for small but finite pressure perturbations, to predict the behaviour of fast-response pressure probes in turbomachinery for gas and ORC power systems. The probe step-response is found to present significant damping due to non-linear wave propagation. Non-idealities in the close proximity of the liquid-vapour curve increase the signal damping due to non-monotone variations of the speed of sound. A simplified approach is proposed to predict the probe dynamic characteristics in ideal regime. The estimation of the probe dynamics in non-ideal regime is found to be very critical and to strongly depend on the thermodynamic state of the fluid. The present results provides a guideline for the design of fast-response pressure probes to be used e.g. past the rotor stage of ORC turbine vanes. Design and modelling of a small scale biomass-fuelled CHP system based on Rankine technology Márcio A. Santos, Jorge C. André, Ricardo A. Mendes, José Baranda Ribeiro Abstract: The ultimate aim of the project, where the work presented in this paper is inserted, is the design of an ORC based cogeneration biomass-fired mini scale CHP system (10-100kWe). For this purpose a medium range (500-5000 kWt) biomass boiler will be modified in order to use part of the energy contained in biomass combustion gases to, indirectly, evaporate the working fluid of an ORC which condenser will be responsible for pre-heating the water demanded by the users. The work presented in this paper refers to the development of a model capable of predict with accuracy the quasi-steady behavior of the ORC by affording an adequate engineering understanding of the physical phenomena affecting their performance. A good and satisfactory agreement was obtained between experimental results and computational outputs of sub-models which allow simulating with some confidence other different conditions.     Building 28 First floor