Dilution refrigeration with a double mixing chamber

At very low temperature, the efficiency of dilution refrigeration heat exchangers is strongly affected by the Kapitza resistance effect. However, it is possible to avoid this drawback by exchanging heat directly in liquid phase. This is done in the 4He cycling refrigerators. Another way to do it is to use a multiple-mixing chamber system. The experiments performed with two mixing chambers connected to an usual dilution refrigerator are described. One can remark that the first mixing chamber works like a perfect heat exchanger since the quantity of heat exchanged is not limited by large thermal resistance, and as a consequence, the minimum temperature is obtained for the highest flow rate. That is an interesting point since one can have high cooling power at the lowest temperature. In practice, other interests of this system are the relatively small number of parameters which enter the calculation and its simplicity of construction. (Kobatake, H