Performance investigations of a single-stage metal hydride heat pump

摘要

This paper discusses the performance investigations of a single-stage metal hydride heat pump (SS-MHHP) working with five different alloy pairs, namely, MmNi_(4.6)Al_(0.4)/ MmNi_(4.6)Fe_(0.4), LaNi_(4.61)Mn_(0.26)Al_(0.13)/La_(0.6)Y_(0.4)Ni_(4.8)Mn_(0.2), LmNi_(4.91)Sn_(0.15)/Ti_(0.99)Zr_(0.01)V_(0.43)-Fe_(0.09)Cr_(0.05)Mn_(1.5), LaNi_(4.6)Al_(0.4)/MmNi_(4.15)Fe_(0.85) and Zr_(0.9)Ti_(0.1)Cr_(0.9)Fe_(1.1)/Zr_(0.9)Ti_(0.1)Cr_(0.6)Fe_(1.4). The performance of the system is predicted by solving the unsteady, two-dimensional coupled heat and mass transfer processes in metal hydride bed of cylindrical configuration using a fully implicit finite volume method. The influences of operating temperatures such as heat source (T_H), heat sink (T_M) and refrigeration (T_C) temperatures on the coefficient of performance (COP) and specific cooling power (SCP) of the system are presented. The predicted hydride bed temperature profiles are compared with the experimental data reported in the literature and a reasonably good agreement is observed between them. The optimum operating temperature ranges of each pair of alloys are suggested. For the selected operating temperatures, a maximum COP of 0.66 is predicted for Zr_(0.9)Ti_(0.1)Cr_(0.9)Fe_(1.1)/Zr_(0.9)Ti_(0.1)Cr_(0.6)Fe_(1.4) hydride pair, while LmNi_(4.91)Sn_(0.15)/Ti_(0.99)Zr_(0.01)V_(0.43-) Fe_(0.09)Cr_(0.05)Mn_(1.5) hydride pair produces the highest SCP of 53.25 W/kg of total mass of the system.