Amplifying the power density in thermoacoustic systems using a spring component

This paper deals with the introduction of a spring component into a thermoacoustic system to increase the power density. This enables more compact and cheaper thermoacoustic systems. A theoretical and experimental study is presented to demonstrate the effect of the introduction of a spring component to amplify the thermal power in a thermoacoustic heat pump. The required spring constant is determined using an electrical circuit analogy model and a DeltaEC model of an existing heat pump. This is calculated for two locations in the system at the cold and hot side of the regenerator. The theory of the deflection of an elastic membrane loaded by a uniform pressure differential is used to calculate the required pretension of an elastic membrane used as spring to obtain the required spring constant. Elastic membranes are prepared and tested in the heat pump. The experimental results show that the insertion of the membrane at the hot side of the regenerator increases the power density by about 20%. The implementation of the membrane at the cold side of the regenerator increases the thermal power by about 100%. For both cases the improvement in the coefficient of performance is about 10%.