Numerical study of the heat transfer in a miniature Joule-Thomson cooler

Abstract

Miniature Joule-Thomson (J-T) cooler is widely used in the electronic industry for thermal management of power intensive electronic components due to its special features of having a short cool-down time, simple configuration and having no moving parts.In this thesis, the sophisticated geometry of the Hampson-type J-T cooler is analyzed and incorporated into the simulation, so that the model can be used as a design tool. The governing equations of the cryogen, helical tube and fins, and shield are coupled and solved numerically under the steady state conditions, and yield agreements with the published experiments to within 3%. The characteristics of flow within the capillary tube and external return gas are accurately predicted. The temperature versus entropy, cooling capacity versus load temperature, and cooling capacity versus input pressure charts are plotted and discussed. The conventional way of simulating a Hampson-type J-T cooler, which is accompanied by a host of empirical correction factors, especially vis-? -vis the heat exchanger geometry could now be superseded. The effort and time spent in designing a Hampson-type J-T cryocooler could be greatly reduced. By avoiding the use of empirical geometric correction factors, the model provides the real behaviors during simulation.