Metal Hydride Heat Pumps for Upgrading Spacecraft Waste Heat

Spacecraft waste heat may be upgraded using a metal hydride heat pump. Thermodynamic analysis is used to choose suitable hydride pairs and to estimate system efficiency; promising reductions in radiator weight are indicated: To investigate whether such reductions can be realized in practice, the dynamic response of two coupled hydride beds is modeled accounting for heat transfer, absorption kinetics, and hydrogen flow. Parametric calculations are reported for the Mg2.4Ni/LaNi4.9Al0.1 pair, which show an optimal cycle time of 10 similar to 12 min. Actual radiator weight savings prove to be substantially less than thermodynamic analysis estimates. Use of hydride heat pumps shows possible merit only in the case of high sink temperatures when using hardened radiators.