Temperature stability of a Joule-Thomson microcooler operating with pure and mixed gases

Benefiting from the developments in micromachining technologies, Joule-Thomson (JT) cryogenic coolers have been miniaturized for cooling cold electronics based either on semiconductor, superconductor, or a combination of the two. The performance of these electronics is affected not only by temperature but also by temperature stability; however, many problems related to the temperature stability of JT microcoolers have not been solved. In this study, we investigate experimentally the performance of a JT microcooler operating with pure nitrogen gas, nitrogen/methane mixture, and nitrogen/ethylene mixture. The cool-down curves and the cooling powers of the microcooler operating with the three types of working fluids between 0.1 MPa and 6.0 MPa are presented. Based on the cooling power measurements, the effect of heat load on the temperature stability of the microcooler is discussed. The microcooler operating with nitrogen/ethylene mixture demonstrates the best temperature stability due to its characteristics of vapor-liquid-liquid equilibrium. Besides the properties of the working fluids, the degree of change in mass-flow rate of the microcooler also affects the temperature stability. This study is conducted to promote the widespread use of cryogenic electronics that are sensitive to the temperature fluctuation.