Numerical analysis of a thermally driven thermoacoustic heat pump for low grade heat recovery

Abstract

This paper presents the numerical design and analysis of a thermally driven thermoacoustic heat pump, which aims to utilise industrial waste heat to provide air-conditioning for buildings where waste heat are abundant but air conditioning is required. The working gas is helium at 3.0 MPa. The operating frequency is around 100 Hz. A three-stage travelling wave thermoacoustic engine is design to convert waste heat to acoustic power, and a single stage travelling wave thermoacoustic cooler is connected to the engine to provide cooling at a temperature of -4 ?C for air conditioning. The ambient temperature is set as 40 ?C. A system with symmetric geometric configuration was initially modelled and validated by published experimental data. The asymmetric impedance distribution was observed, and then an asymmetric system which has different geometric dimensions at each stage was modelled to improve the acoustic conditions within the system. The simulation results show that the overall energy efficiency (defined as the ratio of the cooling power divided by the total heat input) of the tested system for the given temperature range can reach 15-17%, which shows the feasibility and potential for developing thermally driven thermoacoustic heat pump system for utilising waste heat to produce air-conditioning