Measurement of the performance of very high effectiveness heat exchangers

Heat exchangers with very high effectiveness, typically greater than 95%, are required in all cryocoolers. Conventional experimental methods cannot be used for the determination of the effectiveness of cryogenic heat exchangers since the uncertainty in temperature measurement typically 0.1 K at room temperature to 0.3 K at cryogenic temperatures can result in an uncertainty of 1 to 2% in effectiveness. In this work we present the experimental results using a method in which the ineffectiveness of the heat exchanger is measured directly by evaporating liquid nitrogen and compare the results with analytical predictions that also take into account the heat leak through the multilayer insulation.