Maximum entropy generation rate in a heat exchanger at constant inlet parameters
Abstract
The main goal of the paper is to provide a condition for which a maximum entropy generation occurs in a heat exchanger at constant inlet parameters (temperatures and mass flow rates). Knowing this condition is essential during the design of the heat exchanger as it allows designers to avoid one of its most unfavourable operating conditions in terms of thermodynamics. Entropy generation resulting from the resistance of heat-transferring fluids to flow was not taken into account. Entropy generation was analysed as a function of a heat flow rate at constant parameters at the inlet of a condenser and a counter-flow double-pipe heat exchanger. The analysis showed that for the condenser the entropy generation rate increases with the increase in the heat flow rate. The maximum entropy generation rate occurs for the maximum flow rate of the heat that can be transferred according to the definition of heat transfer effectiveness. For the counterflow heat exchanger, the entropy generation as a function of the heat flow rate reaches maximum at constant inlet parameters (temperatures and mass flow rates). It appeared that the peak entropy generation, or the largest exergy loss, occurs when the outlet temperatures of the fluids are equal. This assertion was verified against data obtained from a simulator of the counter-flow heat exchanger for two different relations between heat capacity rates.
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Author Biographies
Rafał Laskowski received his M.Sc. degree in Mechanical Engineering and next Ph.D degree at the Warsaw University of Technology, in 2002 and 2009, respectively. He is a researcher at Faculty of Power and Aeronautical Engineering at the Warsaw University of Technology, where currently he works as an assistant professor. His scientific interests focus on problems concerning mathematical modeling of power plant and their components like heat exchangers, gas and steam turbines. He has published more than 60 scientific papers in various international and national journals, book chapters, and conference proceedings.
Maciej Jaworski received his M.Sc. and Ph.D. degrees in Mechanics and D.Sc. in Power Engineering from Warsaw University of Technology (WUT) in 1983, 1998 and 2015 respectively. Currently he works as Associate Professor in the Institute of Heat Engineering, at the Faculty of Power and Aeronautical Engineering, WUT. His scientific interests focus on thermodynamics (e.g. analysis of thermal devices on the base of the second law), heat transfer (e.g. interaction of laser radiation energy of extremely high intensity with matter) and thermal energy storage problems (especially the applications of phase change materials in different engineering areas). He has participated in many international and national research projects. Currently he is involved in H2020 project aiming at the development of PhD program on Thermal Energy Storage. He has published more than 100 scientific papers in various international and national journals and conference proceedings, he is co-author of several books on thermodynamics and heat transfer.
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