Performance investigation of double-stage metal hydride based heat pump

In this paper, the performance investigation of a Double-Stage Double-Effect Metal Hydride Heat Pump (DSDE-MHHP) working with LaNi4.1Al0.52Mn0.38, LmNi4.91Sn0.15 and Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5 hydride alloys is presented. The effects of half cycle time (θ), hydride mass ratio (MR), sensible heat exchange factor (ϕ) and operating temperatures, viz. heat source (TD), heat sink (TM), and refrigeration (TC) temperatures on the amount of hydrogen transferred between the paired reactors, coefficient of performance (COP) and specific cooling power (SCP) of the DSDE-MHHP system are investigated. For the present analysis the heat rejection temperature (TH) is maintained constant at 373 K. Numerically predicted hydride bed temperatures are compared with experimental data and a good agreement is observed between them. It is observed from the numerical results that the COP and SCP of the DSDE-MHHP system increase with heat source and refrigeration temperatures, and decrease with heat sink temperature. For operating temperatures of 578, 373, 298 and 283 K (TD, TH, TM and TC), the average COP and SCP of the system are found to be 0.81 and 48.1 W/kg of total alloy mass, respectively.