Evaluation of metal hydride machines for heat pumping and cooling applications

Three different schemes of metal hydride solid sorption devices for heat pumping and cooling applications are presented and compared based on theoretical evaluations. Key parameters obtained from experimental and simulation results from coupled metal hydride reaction beds have been used for the theoretical evaluation. The single (HS) and double stage (HD) devices show reasonable performances, but they require many moving parts. Using high performance reaction beds, e.g. a capillary tube bundle reaction bed, cycle times of about 5-10 min can be obtained with these devices. This corresponds to a specific power output of 100-200 W kg(-1) (HS) or 150-300 W kg(-1) (HD), referred to the total hydride inventory of the machine. The multi-hydride-thermal-wave (HW) system has a lower specific power output, but it offers significant advantages like modest hardware effort, low pumping power and a very wide operating temperature range. (C) 1998 Elsevier Science Ltd and IIR. All rights reserved.