Thermodynamic Analysis and Optimization Design of Heat Exchanger

Abstract

In order to address the contradiction between the limited fossil fuel reserves and sharp increase of huge energy demand from the world economy and people’s daily lives, there is an urgent need to develop energy saving measures. Heat exchanger as a device for heat transfer from one medium to another is widely applied in power engineering, petroleum refineries, chemical industries, food industries, and so on. Therefore it is of great value to improve the heat exchanger performance and save energy in heat exchange processes. Recently with the aim of reducing the unnecessary heat dissipation in heat exchange processes, we have studied thermodynamic analysis and optimization design of heat exchangers. Firstly based on the genetic algorithm and the improved entropy generation number which avoids the ‘entropy generation paradoxes’ induced by the original entropy generation number, we proposed an improved entropy generation minimization approach for heat exchanger optimization design. Secondly, we found that the entransy is a state variable and the second law of thermodynamics can be described by the entransy and entransy dissipation, this work places the entransy dissipation theory on a solid thermodynamic basis. Thirdly, based on the entransy dissipation theory we derived the expression of the local entransy dissipation rate for heat convection, developed variational principles for heat transfer and showed that this principle is compatible with the Navier–Stokes–Fourier equations. Fourthly, based on the entransy dissipation theory, we proposed a heat exchanger performance evaluation criterion called the entransy dissipation number and established a principle of entransy dissipation equipartition for heat exchanger optimization designs. Finally, we developed an entransy dissipation minimization approach for heat exchanger optimization design and applied it to the tube-and-shell heat exchanger optimization design.