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Energies 2015, 8(6), 5488-5515; doi:10.3390/en8065488

Performance Analysis of an Evaporator for a Diesel Engine–Organic Rankine Cycle (ORC) Combined System and Influence of Pressure Drop on the Diesel Engine Operating Characteristics

1
College of Environmental and Energy Engineering, Beijing University of Technology, Pingleyuan No. 100, Beijing 100124, China
2
Collaborative Innovation Center of Electric Vehicles in Beijing, Pingleyuan, No. 100, Beijing 100124, China
3
State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Qinghuayuan, Beijing 100084, China
*
Author to whom correspondence should be addressed.
Academic Editor: K. T. Chau
Received: 1 May 2015 / Revised: 26 May 2015 / Accepted: 1 June 2015 / Published: 8 June 2015

Abstract

The main purpose of this research is to analyze the performance of an evaporator for the organic Rankine cycle (ORC) system and discuss the influence of the evaporator on the operating characteristics of diesel engine. A simulation model of fin-and-tube evaporator of the ORC system is established by using Fluent software. Then, the flow and heat transfer characteristics of the exhaust at the evaporator shell side are obtained, and then the performance of the fin-and-tube evaporator of the ORC system is analyzed based on the field synergy principle. The field synergy angle (β) is the intersection angle between the velocity vector and the temperature gradient. When the absolute values of velocity and temperature gradient are constant and β < 90°, heat transfer enhancement can be achieved with the decrease of the β. When the absolute values of velocity and temperature gradient are constant and β >90°, heat transfer enhancement can be achieved with the increase of the β. Subsequently, the influence of the evaporator of the ORC system on diesel engine performance is studied. A simulation model of the diesel engine is built by using GT–Power software under various operating conditions, and the variation tendency of engine power, torque, and brake specific fuel consumption (BSFC) are obtained. The variation tendency of the power output and BSFC of diesel engine–ORC combined system are obtained when the evaporation pressure ranges from 1.0 MPa to 3.5 MPa. Results show that the field synergy effect for the areas among the tube bundles of the evaporator main body and the field synergy effect for the areas among the fins on the windward side are satisfactory. However, the field synergy effect in the areas among the fins on the leeward side is weak. As a result of the pressure drop caused by the evaporator of the ORC system, the diesel engine power and torque decreases slightly, whereas the BSFC increases slightly with the increase of exhaust back pressure. With the increase of engine speed, power loss, torque loss, and BSFC increment increase gradually, where the most significant change is less than 1%. Compared with the diesel engine itself, the maximum increase of power output of the diesel engine–ORC combined system is 6.5% and the maximum decrease of BSFC is 6.1%. View Full-Text
Keywords: organic Rankine cycle; diesel engine; evaporator; simulation; field synergy; exhaust back pressure organic Rankine cycle; diesel engine; evaporator; simulation; field synergy; exhaust back pressure
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Bei, C.; Zhang, H.; Yang, F.; Song, S.; Wang, E.; Liu, H.; Chang, Y.; Wang, H.; Yang, K. Performance Analysis of an Evaporator for a Diesel Engine–Organic Rankine Cycle (ORC) Combined System and Influence of Pressure Drop on the Diesel Engine Operating Characteristics. Energies 2015, 8, 5488-5515.

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