Combination effect of stacks as a heat pump on the thermoacoustic cooling system

The cooling effect of the thermoacoustic cooling system with various stacks, as a heat pump, with different lengths and channel radii is experimentally investigated. Loop-tube is employed as the thermoacoustic cooling system and air is filled at atmospheric pressure as working fluid. Two stacks, stacks 1 and 2, sandwiched between heat exchangers, are placed in the loop-tube. Stack 1 is employed as a prime mover and stack 2 as a heat pump. A stack is 50mm-long honeycomb ceramic. Three kinds of stacks with different channel radii are used: 0.55 mm, 0.45 mm and 0.35 mm. The length and the channel radius of stack 1 are fixed to investigate the influence of stack 2 on the cooling effect. Temperature decrease at the cooling point is observed with stacks with various lengths and channel radii. For stack 2, one or plural stacks are used. Plural stacks are in combination of stacks with same channel radii or with different channel radii. The maximum temperature decrease of 17.9 degrees C has been observed when a 0.45mm-channel-radius stack on the side of the reference temperature and a 0.35mm-channel-radius stack on the side of the cooling point have been combined. It has been confirmed that more temperature decrease can be obtained with combined stacks with a smaller-channel-radius stack on the side of the cooling point and a bigger-channel-radius stack on the side of the reference temperature. The results shows that combined plural stacks, as a heat pump, with different channel radii have a good influence on the cooling effect of the thermoacoustic cooling system.