Reactor design and numerical study on metal hydride based finned reactor configurations for hydrogen compression application

Abstract

The present study is focussed on the design and development of a single stage metal hydride hydrogen compressor. A 0.5 kg alloy mass capacity reactor is designed to withstand 100 bar at 120 °C. The Von Misses equivalent stress is calculated for the designed reactor and it is found to have a design margin of 11.4%. The reactor has an excellent weight ratio of 2.22. To enhance the thermal performance of the reactor, extended surfaces are incorporated. A numerical model is developed to compare the performance of three different fin configurations namely longitudinal fins, transverse fins and spiral fins. Longitudinal fins are found to provide better thermal enhancement during initial period of absorption half cycle. However, transverse fins showed better performance in the desorption case. Nevertheless, as the time progresses all the fin configurations showed similar performance under different operating temperatures. Further, hydrogen discharge rate is studied at various discharge pressure to understand the requirements while coupling with an empty cylinder or fuel cell. The study revealed that a 0.5 kg reactor can discharge hydrogen at the rate of 2.27 lpm for 2000 s when discharged to fill a cylinder up to 10 bar. The compression rate of the developed compressor is found to be 136 l/h at 10 bar discharge pressure and 373 K heat source temperature. The isentropic efficiency of the compressor is found to be 11.5%.