STRESS INDUCED PHASE CHANGING MATERIAL FOR THERMOACOUSTIC REFRIGERATION

ABSTRACT

A novel concept to use a stress induced phase transformation in NiMnGa for solid state refrigeration is investigated. The stress needed to induce a phase transformation was measured at temperatures from 24 to 60°C. The stresses were sufficiently low enough such that an acoustic wave can in theory induce the phase transformation. DSC measurements were done on the NiMnGa material to measure the latent heat that can be absorbed and release. Theoretical calculations of the coefficient of performance for a heat pump using this stress induced thermal phenomena showed a possible efficiency of 67%. A solid state heat pump using a piezoelectric or magnetostrictive transducer to generate the acoustic pressure wave and a fluid medium suspended with NiMnGa nanoparticles is suggested as a possible implementation of the concept.

Keywords:

• NiMnGa
• ferromagnetic shape memory
• thermoacoustic
• refrigeration
• phase change
• cooling

ACKNOWLEDGMENTS

The authors of this paper gratefully acknowledge the financial support of DARPA and ARL in funding this work under a Phase I SBIR effort.