Numerical analysis of clogging dynamics in micromachined Joule-Thomson coolers

Micromachined Joule-Thomson (JT) coolers are of interest for cooling small electronic devices. The long-term performance of JT microcoolers is limited by the clogging phenomenon caused by the deposition of water molecules present as impurity in the working fluid. This work investigates the clogging dynamics in a JT microcooler operating with nitrogen gas. A numerical model is developed to calculate the temperature profile and the deposition rate of water molecules along the counter flow heat exchanger and the restriction of a microcooler. The deposition process is modeled by considering the diffusion of water molecules in nitrogen gas and the kinetic process of water molecules on wall surface, which are both temperature dependent. Numerical results show that the clogging rate during cool down is influenced by gas impurity and gas pressure. The effects of gas purity, gas pressure and cold-end temperature on the continuous operating time of the microcooler are also investigated.