Abstract
Waste heat recovery is an effective method for improving engine efficiency. While most research on waste heat recovery from heavy-duty engines focuses on the high-temperature heat sources, this paper investigates the performance of a low-temperature system. The experimental setup features an organic Rankine cycle with R1233zd(E) as the working fluid recovering heat from the coolant of a heavy-duty Diesel engine. Experiments at multiple engine operating points indicated a maximum operating cycle pressure of 8 bar and temperature of 92 °C. Between 0.1 and 0.7 kW net shaft power was achieved with a thermodynamic efficiency between 1.1 and 1.8%, resulting in a maximum expander power of 0.7% relative to the engine power. A simple empirical model based on the experimental results indicated that approximately 0.7% of the engine’s energy could be recovered during a driving cycle, rising to 1.3% if a high efficiency pump and expander are used. The main contribution of this paper lies in the presentation of the experimental setup and experimental results specifically dedicated to recovering the heat from the engine coolant, which permits realistic evaluation of the performance.
Highlights
Global concern over rising CO2 emissions and their effects on climate change has led to regulations mandating emission reductions in all relevant sectors
This paper presents an experimental evaluation of the performance of a LT-waste heat recovery (WHR) system and uses the experimental results to develop a simple empirical model to evaluate the system performance over a driving cycle
This paper presents the performance of a low-temperature waste heat recovery system coupled to a heavy-duty engine in which R1233zd(E) was used as the working fluid to extract heat from the engine coolant
Summary
Global concern over rising CO2 emissions and their effects on climate change has led to regulations mandating emission reductions in all relevant sectors. Short-term solu tions include increasing combustion efficiency, alternative fuels, loss reduction, electrification, and waste heat recovery (WHR) [3]. WHR systems for internal combustion engines typically target high-temperature (HT) heat sources (e.g. the exhaust gas recirculation (EGR) cooler and the exhaust gas) due to their high heat content and temperature, while low-temperature (LT) heat sources (e.g. the coolant, the charge air cooler (CAC), and the lubricant oil) are ignored because of their lower temperature and potential [4]. This paper focuses on waste heat recovery from the engine coolant of a heavy-duty Diesel engine. An opportunity to enhance the quality of the energy of the engine coolant is to raise its temperature, which could improve the performance of WHR systems or allow the use of higher condensation temperatures without reducing system performance. While raising the coolant temperature could adversely affect engine performance, coolant temperatures as high as 140 ◦C did not significantly impact the engine efficiency in experimental studies [12]
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