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11:00   Session 2 – Waste heat recovery from engines I
Chair: Andrea De Pascale
11:00
20 mins 		System-search APPLICATION OF REFRIGERANT WORKING FLUIDS FOR MOBILE ORGANIC RANKINE CYCLE SYSTEMS
Chris Nelson
Abstract: Cummins Inc. has been a leading developer of ORC systems for application to heavy-duty, on-highway trucks in the United States for several years. Cummins has passed through several generations of ORC system architecture and has fielded several on-highway vehicles equipped with ORC systems as a part of research conducted in partnership with the United States Department of Energy. Throughout this development, Cummins has carefully evaluated potential working fluids for its ORC systems and has remained committed to using safe and environmentally friendly refrigerants such as R245fa and its recently introduced ultra-low GWP replacements. Integration of Organic Rankine Cycle (ORC) systems into heavy duty, on-highway vehicles requires consideration of a significant number of factors, not the least of which is the choice of working fluid. The selection of fluid is primarily driven by potential performance considering the application at hand, potential environmental and health effects of the fluid, safety, availability, serviceability, etc. Given the working fluid, selection of various system components and optimization of system architecture may be made. This paper will present a brief review of Cummins’ ORC history and discuss background leading to Cummins Inc.’s selection of and adherence to refrigerant working fluids for mobile application. Details of technology that allow refrigerant’s safe and effective use will also be discussed. A performance comparison between R245fa, ultra-low GWP replacements, and ethanol will be presented and an architecture comparison between refrigerant and ethanol systems will be provided. Options and considerations for further development and commercialization of the technology will also be briefly discussed.
11:20
20 mins 		System-search IMPROVING TRAIN ENERGY EFFICIENCY BY ORGANIC RANKINE CYCLE (ORC) FOR RECOVERING WASTE HEAT FROM EXHAUST GAS
David Serrano, Pascal Smague, Paolino Tona, Pierre Leduc, Arthur Leroux, Andre-Charles Mintsa, Philippe Chevalier
Abstract: In a context of energy cost increase, reducing engine fuel consumption has become a key issue for transportation industry. Many paths exist to achieve substantial fuel savings: downsizing, hybridization, energy recovery… IFPEN has carried out an analysis of heat losses showing that recovering exhaust heat energy is a promising solution for improving fuel economy. Thus, IFPEN and ENOGIA have co-developed an Organic Rankine Cycle (ORC) system for direct recovering energy from exhaust heat. This system has been designed in order to be implemented on a Diesel-electric regional train manufactured by ALSTOM TRANSPORT. The train has several Diesel engines that produce mechanical torque needed for generators used for train electric propulsion. The ORC recovers energy from the exhaust heat of the different Diesel engines. The project funded by the French national agency for research (ANR) started with 0D simulations in order to identify the optimal ORC architecture as well as some promising working fluids. More than 100 fluids were evaluated and finally two fluids were retained for this application thanks to their safety features, eco-friendliness and thermodynamic potential. A pre-design study defined the main components (boiler, condenser, pump…) that answer to the major constraints: cost, compactness, efficiency. ENOGIA developed the “heart” of the ORC, a dedicated turbine coupled with a high-speed generator on the same axle. The objective is that the electricity produced by the turbo-generator is re-injected for the train electrical propulsion. An ORC prototype has been assembled with a special care for avoiding any organic fluid leaks. The prototype has then been tested in an engine bench with the same Diesel engine as in the regional train. At the engine bench, the electricity produced by the ORC is re-injected in the French grid by means of inverters and transformers. Based on previous experiences, IFPEN has developed an advanced control system for this application, which allows transient control of ORC operation by regulating vapor superheating at evaporator outlet. The machine has been largely instrumented for monitoring Rankine cycle operation. At the time of paper writing, around 10kW of ORC electricity output power has been reached in stable conditions.
11:40
20 mins 		System-search PERFORMANCE ANALYSIS OF WASTE HEAT RECOVERY WITH A DUAL LOOP ORGANIC RANKINE CYCLE SYSTEM FOR DIESEL ENGINE
Hongjin Wang, Hongguang Zhang
Abstract: Given the low utilization rate of an internal combustion engine（ICE）, only 40% at most is used as an effective power output and the remaining is released into the air in the form of waste heat within exhaust gas and coolant liquid[1]. This not only causes a huge amount of energy dissipation but also brings serious environmental contamination, therefore it has assumed great significance to investigate how to recover and utilize some of the lost available work from ICE. Waste heat resources in ICE are low- or medium-grade energy, while the organic Rankine cycle (ORC) system is a promising technology of converting low- or medium-grade waste heat into useful work[2]. To take full advantage of the waste heat from a diesel engine, a set of dual loop organic Rankine cycle system was designed to recover exhaust energy, waste heat from the coolant system, and released heat from turbocharged air in the intercooler of a six-cylinder diesel engine. Aspen plus software was used to model the dual loop ORC system. According to the simulation model, the operating performance of the dual loop ORC system and the fuel economy of the diesel engine were investigated. The results show that the thermodynamic performance and economy performance of the diesel engine can be effectively improved by using the dual loop ORC system. Under the certain engine operating conditions, namely, engine speed is 2000 r.min-1 and engine torque is 1313 N.m, the total net power output of the dual loop ORC system is up to 43.65 kW. The brake specific fuel consumption (BSFC) and the thermal efficiency of the diesel engine-dual loop ORC system are 191.24g/kW.h and 37.57%, respectively. Compared with the diesel engine, the thermal efficiency of the combined system can be increased by 13.69% and the BSFC can be reduced by 15.86%.
12:00
20 mins 		System-search POTENTIAL OF SMALL-SCALE TURBOMACHINERY FOR WASTE HEAT RECOVERY ON AUTOMOTIVE INTERNAL COMBUSTION ENGINES
Kévin Rosset, Violette Mounier, Eliott Guenat, Olivier Pajot, Jürg Schiffmann
Abstract: This paper investigates the waste heat recovery potential of internal combustion engines, using organic Rankine cycles running on small-scale radial turbomachinery. ORC are promising candidates for low-grade thermal sources and the use of dynamic expanders yields very compact systems, which is advantageous for automotive applications. As engine coolant and exhaust gases are the major available heat sources, different cycle configurations and working fluids have been investigated to capture them, in both urban and highway car operation. Pareto fronts showing the compromise between net power output and total heat exchange area have been identified for a set of cycle’s variables including turbine inlet conditions and heat exchanger pinches. A preliminary optimization, including only R-1234yf working fluid, shows that a single-source regenerative cycle harvesting the high temperature exhaust gas stream performs averagely better than coolant-driven and dual-source cycles. A more in-depth optimization including eight working fluids as well as aerodynamic and conceptual limitations related to radial turbomachinery and automotive design constraints, finally shows that an ICE exhaust heat recovery ORC could improve the first law efficiency of the driving system by up to 10% when implemented with fluid R-1233zd.
12:20
20 mins 		System-search PARAMETRIC OPTIMIZATION AND PERFORMANCE ANALYSIS OF ORGANIC RANKINE CYCLE (ORC) FOR ENGINE WASTE HEAT RECOVERY
Fubin Yang, Hongguang Zhang
Abstract: In China, internal combustion engines (ICEs) have consumed over 66 percent of total fuel consumption. Several methods have been adopted for the engine waste heat recovery, therein, the organic Rankine cycle (ORC) can be used to recover waste heat from an ICE with its flexibility, high efficiency and outstanding economical performance. This study examines the parametric optimization and performance analysis of ORC system using genetic algorithm (GA) for engine waste heat recovery. The effects of three key parameters, including evaporation pressure, superheat degree, and condensation temperature, on the net power output per unit heat transfer area and exergy destruction rate under engine various operating conditions are analyzed. Subsequently, the performances of a finned-tube evaporator used in this ORC system are evaluated. The results indicate that the optimal evaporation pressures are mainly influenced by the engine operating conditions. Moreover, superheat degree and condensation temperature presents slight variation over the whole operating range. The ORC system achieves maximum net power output per unit heat transfer area of 0.74kW/m2. Furthermore, the maximum effective heat transfer area of the evaporator is 69%, which has great influence on the performance of the ORC system.