最小热阻原理在组合式相变材料蓄热过程优化中的应用

Abstract

The minimum thermal resistance principle has been developed in recent years, which represents a new method for optimization of heat transfer processes. In this paper, the minimum thermal resistance principle is further developed for optimization of melting process with multiple phase change materials (PCMs). The general formulas of the optimum melting temperature are deduced on the principle of calculus variation, subject to different optimization objectives. Base on the general formulas, the effects of numbers of PCMs on entransy dissipation-based thermal resistance and thermal performance are discussed. The more PCMs used in melting process can reduce the entransy dissipation-based thermal resistance to improve the thermal performance. The results show that the minimum thermal resistance is suitable for melting process optimization with multiple PCMs. Moreover, the combinational efficiency is defined to estimate the thermal performance for multiple PCMs conveniently. The effects of the number of heat transfer unit and heat capacity flowrate on entransy dissipation-based thermal resistance are investigated. The results indicate that, the combinational efficiency can be increased with increasing of numbers of PCMs, and the entransy dissipation-based thermal resistance can be decreased with increasing of the number of heat transfer unit and heat capacity flowrate, and both of the effects are gradually weakened. Thus, a theoretical guidance is provided for selecting the multiple PCMs and designing flow and structure parameters. In addition, based on the minimum thermal resistance principle, the uniformity principle of temperature difference field is proposed as a new optimization criterion for melting process with multiple PCMs.