Numerical study of a metal hydride heat transformer for low-grade heat recovery: Simulation of a MH heat transformer

Due to the increasing demand for clean energy and improved energy utilization, the metal hydride heat transformer for low-grade heat recovery has attracted wide attentions recently. In this paper, such a system with LaNi5–LaNi4.7Al0.3 pair, which is used for upgrading waste heat to a higher temperature, was investigated in detail by numerical simulation. Different from existing studies, in this investigation only ambient and waste heat sources are involved during operation of the heat transformer, which could be advantageous in many aspects. A rigorous 2-D unsteady model was developed and numerically solved by the fully implicit finite volume method (FVM). It was shown that the proposed system can achieve steady heat upgrading operation, resulting in an average temperature boost of 6.8 K using a 358 K waste heat source. The dynamic behavior of the heat transformer in three subsequent cycles was analyzed, and the measures aiming at continuous output were further discussed.

► We model a metal hydride heat transformer using only ambient and waste heat sources. ► The effects of vessel wall and minor reaction were considered. ► Steady heat upgrading can be achieved by the proposed system. ► Measures were presented to improve the symmetry in output and regeneration time. ► Performance of the proposed heat transformer is competitive.