On the performance of copper foaming metal in the heat exchangers of pulse tube refrigerator

As key components in pulse tube refrigerators (PTRs), heat exchangers have great influence on the performance of the PTRs, especially the cold end heat exchangers which dominate the cooling effect between the cold gas and heat load. Filling copper screens are widely used to improve the performance of heat exchange and laminar flow. Whereas, the heat transfer rate of copper screens is still not good enough for the actual requirements of PTRs. Furthermore, the flow resistance of the copper screen is growing up quickly with the increase of screen mesh. In this paper, we propose a new type of copper foaming metal with high heat transfer area and low flow resistance in the heat exchanger instead of the copper screens. The heat transfer performances of the copper screens and the copper foaming metal are firstly compared by theoretical calculation, which shows that the performance of the copper foaming metal with 600 μm pore size is better than that of 20 and 80 mesh copper screens, verified by experimental results. A four valve pulse tube refrigerator (FVPTR) with copper foaming metal of 600 μm pore size as filling material of the heat exchanger achieved 69.5 K, 2.5 K lower than that of using 20 mesh copper screens, 1.7 K lower than that of using 80 mesh copper screens.