Minimization of the Total Area of Heat Exchangers in Refrigeration Systems Based on the Entransy Theory

In order to reduce the consumption of energy and material, the optimization design of the refrigeration systems, especially the minimization for the total area of the heat exchangers, has been an attractive but tough issue in both research and engineering fields. Therefore, the entransy dissipation theory is introduced in this article to analyze the refrigeration systems. The systems are analyzed through the entransy dissipation analysis for the irreversible heat transfer processes in the heat exchangers and the thermodynamic analysis for the compressors and expanders, which are combined to deduce the mathematical relation between the known conditions, i.e. inlet temperatures of fluids, the heat absorbed from the cold end of the systems, and the design parameters, i.e. the heat conductances of heat exchangers and heat capacity rates of working fluids. Based on the relation, the optimization design for the refrigeration systems is converted to the conditional extremum problem that offers the optimization equations group. Solving the equations yields the optimal configuration of all the design parameters. Then a typical refrigeration system is numerically optimized to obtain the optimal configuration, optimal compression ratio and the minimum for the total area of heat exchangers, which is proved to be the least through the comparison with other configuration of the design parameters.