Performance Analysis of a Metal Hydride Based Heat Transformer

B. Satya Sekhar, P. Muthukumar


A thermal model for predicting the performance of a single-stage metal hydride based heat transformer (MHHT) is presented. The pair of metal hydrides chosen for the present study is LaNi4.7Al0.3 and LaNi5.The performance of the system is predicted by solving the combined energy and mass (heat and hydrogen) transfer equations during absorption and desorption of hydrogen to/from the hydride bed in cylindrical coordinates. Numerical results are compared with the experimental data reported in the literature, and a good agreement is found between them. The effects of operating temperatures such as heat source (TM), heat output (TH) and heat rejection (TL) temperatures on the system performances in terms of coefficient of performance (COPHT), specific heating power (SHP) and second law efficiency (ηE) are investigated. For the given range of operating parameters, there exist the optimum values of bed thickness and bed effective thermal conductivity. The COPHT and SHP are found to increase with heat source temperature and however, both are found to decrease with heat output temperature. At the operating conditions of TH = 423, TM = 383 K and TL = 303 K, the COPHT and SHP of the MHHT are found to be 0.415 and 46 W/kg of alloy, respectively. Higher TL yields better ηE while its value is found to be lower at higher TM.


Coupled heat and mass transfer, Heat transformer, metal hydrides, performance analysis, thermal model

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