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15:00   Session 13: Waste heat recovery from engines II
Chair: Arnaud Legros
15:00
20 mins 		System-search STUDY ON THE INFLUENCE OF EVAPORATOR OF ORC SYSTEM ON ENGINE PERFORMANCE
Chen Bei, Hongguang Zhang
Abstract: Of the engine’s fuel combustion energy, only about one third is converted into mechanical energy and the remaining is dissipated in the form of waste heat through the exhaust and the coolant system [1]. Organic Rankine cycle (ORC) is an effective method for waste heat recovery and has been widely applied in many domains. Baik et al propose that the heat-transfer performance of the exchanger has a significant impact on the output power of the ORC [2]. Taking as the heat transfer component of ORC system, evaporator has an impact on ORC system, but also influences engine performance. In this paper, the influences of evaporator of ORC system on engine performance are studied. 3D model of the fin-and-tube evaporator of ORC system is established while CFD numerical simulation is used to obtain the distribution characteristics of the temperature field, the pressure field, and the velocity field of the exhaust in the evaporator shell side. The performance of fin-and-tube evaporator of ORC system is analyzed based on the aforementioned simulation results. Subsequently, a simulation model of the engine is developed based on GT-Power software and the back pressure of exhaust is set based on the pressure drop between import and export of evaporator which is acquired from the simulation result. Moreover, the variation of engine power, torque and brake specific fuel consumption is discussed. Results show that, equipped with the evaporator of ORC system, the engine power and torque decreased slightly while the brake specific fuel consumption increased slightly. On the whole, the influences of the evaporator of ORC system for engine performance are not especially obvious.
15:20
20 mins 		System-search WASTE HEAT UTILIZATION OF MAIN PROPULSION ENGINE JACKET WATER IN MARINE APPLICATION
Errol Yuksek, Parsa Mirmobin
Abstract: As world trade grows, fuel prices increase, and International Maritime Organization (IMO) emissions requirements tighten, there is more demand for the marine industry to employ innovative means of reducing the fuel consumption and emissions of shipping vessels. The main propulsion engines of large shipping vessels produce great quantities of jacket water heat at temperatures below 95 C, but this valuable heat energy is transferred to cooling systems and rejected to the world’s oceans as waste. At the same time, the electrical needs of these vessels are sustained by burning diesel fuel to run generators. To utilize the jacket water waste heat Calnetix Technologies, in partnership with Mitsubishi Heavy Industries (MHI), has developed the HydrocurrentTM 125EJW (Engine Jacket Water) Organic Rankine Cycle (ORC) to convert low-grade heat energy into grid-quality electric power. Large vessels such as tankers, bulk carriers, and container vessels with an engine output of approximately 30 MW can output as much as 300 m3/hr of 80 to 95 C jacket water from their main propulsion engines. When integrated into the jacket water and sea water systems of such vessels, the ORC unit can produce up to 125 kW of gross grid-quality electric power. To produce 125 kW of power, a diesel generator would consume as much as 250 metric tons of diesel fuel per year in addition to its generated emissions and maintenance requirements. Calnetix Technologies has leveraged its core technologies to develop a new high efficiency ORC system that is compact and modular in design. In addition, the ORC unit has been certified by marine classification societies Nippon Kaiji Kyokai (NK) and Lloyd’s Register (LR) for installation on any vessel without modification. The following is a description and validation of the commercially available, class society certified system that has been realized.
15:40
20 mins 		System-search TRANSIENT DUTY CYCLE ANALYSIS FOR MOBILE ORGANIC RANKINE CYCLE APPLICATIONS
Miles Robertson, Aaron Costall, Peter Newton, Ricardo Martinez-Botas
Abstract: Internal combustion engines have high exhaust energy at the tail pipe, and mobile organic Rankine cycle (ORC) systems have been proposed to harness this waste heat, thereby providing a significant opportunity for vehicle CO2 emissions reduction. This paper discusses the impact of transient duty cycles on mobile ORC system performance. A thermodynamic model of an ORC system is presented, which includes a detailed heat exchanger model based on the Effectiveness-NTU method, and which has the ability to account for the thermal capacitance of the ORC system – which is of particular importance during vehicle start-up. Thermodynamic system simulations from start-up were performed based on four transient engine test cycles applied to a simulated 11.7L heavy-duty diesel engine: the Constant-Speed, Variable-Load (CSVL) cycle, the European Transient Cycle (ETC), the Non-Road Transient Cycle (NRTC), and the World Harmonized Transient Cycle (WHTC). For a fixed heat exchanger size, working fluid and ORC mass flow rate, it was found that the relatively high-load CSVL cycle (acting as a surrogate for an off-road machine) produced a peak average power of 9.0 kW from start-up, while the WHTC (representative of on-highway driving conditions) only delivered 3.2 kW. Results also indicate a very narrow band (5.5–6.2%) of peak exhaust energy recovery across all duty cycles, implying a close to linear scaling of ORC system power output with duty cycle intensity and engine size. The choice of vehicle/application is thus constrained by the ability to design an acceptable low-power ORC expander, suggesting that vehicles running the most heavily-loaded duty cycles stand to gain the most benefit from mobile ORC systems.
16:00
20 mins 		System-search THERMODYNAMIC ANALYSIS ON COLD ENERGY UTILIZING ORGARNIC RANKINE CYCLE
Taehong Sung, Sang Youl Yoon, Kyung Chun Kim
Abstract: Organic Rankine cycle (ORC) system is a low-temperature waste heat recovery system. The system configuration is simple and the operating characteristics are also stable. Usually ORC systems emit heat to ambient air or accessible water. In this study, an ORC system which utilizes both low-temperature heat source and cold energy heat sink is thermodynamically analysed. Unlike the typical ORC application, amount of heat source is sufficient for cycle operation (temperature gradient is gradual for heat source), temperature of heat sink is very low, amount of heat sink is also limited (temperature gradient is steep for heat sink). The effect of condensing temperature and exit temperature of heat sink to system power output, mass flow rate, thermal efficiency and exergy efficiency are delineated here. R134a and R1234yf refrigerant working fluids are also compared. Two different heat source temperatures of 45 oC and 80 oC are compared. Heat sink temperature is fixed at -160 oC. In case of sufficient amount of heat source, decrease in condensing temperature results in increase in power output and decrease in refrigerant mass flow rate. At the same time, thermal efficiency and exergy efficiency also are increased due to increase in net work. Thus, the cycle be designed with low condensation temperature considering whether condensing pressure goes bellow ambient pressure (which causes incompressible component penetration into system), whether evaporating pressure is in the range of pressure tolerance of the system, and whether the pressure ratio is realiziable with turbo-machienry devices.
16:20
20 mins 		System-search WATER-BASED RANKINE-CYCLE WASTE HEAT RECOVERY SYSTEMS FOR ENGINES: CHALLENGES AND OPPORTUNITIES
Gunnar Latz, Olof Erlandsson, Thomas Skåre, Arnaud Contet, Sven Andersson, Karin Munch
Abstract: Much of the fuel energy in an internal combustion engine is lost as heat, mainly through hot exhaust gas. The high energy losses, and high temperatures of the exhaust gas, provide favorable conditions for applying a waste-heat recovery system. Among the available options, systems based on the Rankine cycle show the highest potential in terms of reducing fuel consumption. Water or water-based mixtures have several advantages over organic fluids as working fluids for such applications of the Rankine cycle, in terms of cost, thermal stability, safety and complexity of the system. They also have several disadvantages, including possible freezing for pure water, high boiling temperature and high heat of vaporization. Hence, higher temperatures and amounts of waste heat are needed for reliable operation of the system. However, few experimental investigations have addressed the practical challenges associated with water and their effects on the performance and operation of a system in a driving cycle. This paper presents results of experiments with a full-scale system for recovering waste heat from the exhaust gas recirculation (EGR) of a 12.8 L heavy-duty Diesel engine on a test bench. The working fluid used in the experiments was deionized water and a 2-cylinder piston expander served as an expansion device. The engine was kept in standard configuration, except for minor modifications required to implement the heat-recovery system. The prototype EGR boiler was designed to fit in the space initially designated for the production EGR cooler. The assembly was operated in the operating points of the European Stationary Cycle (ESC). The results show that the trade-off between boiling pressure, sufficient superheating of the water and cooling of the EGR caused by the pinch-point in the boiler poses a major challenge when using water as a fluid. Low flow rates at low load points were challenging for boiler stability. During operation, the blow-by of working fluid into the lubrication system of the expander and vice versa was also problematic. Special steam-engine oil with high viscosity and good water separation capability was used to weaken this effect. The Rankine cycle-based test system attained a thermal efficiency of 10% with EGR as the only heat source. Results, major constraints and possible means to improve the system when using water as a working fluid are presented here. Simulation models developed for the EGR boiler and the piston expander supported this effort.