The application of general Joule-Thomson (J-T) coolers in the integrated electronic equipment is limited by its compactness in the heat exchanger and cooling power (a few milliwatts to hundreds of milliwatts). However, the microchannel with pillars has many advantages, such as compact structure, tiny axial thermal conductivity, and large heat transfer area. Besides, when the pressure variation of the fluid is large in the microchannel, the distributed Joule-Thomson effect is generated significantly. Therefore, this study proposed a throttling and heat exchange structure, where heat transfer and throttling coexisted, and fabricated a laminated microchannel distributed J-T cooler with pillars utilizing the processing technology of printed circuit heat exchanger.The refrigeration performance concerning the cold-end temperature, cooling power, and temperature distribution was then investigated through experiments with two refrigerants (argon and nitrogen). The study implies that the temperature difference and cooling power of the cooler both increase with the rise of the inlet pressure with argon, the no-load cold-end temperature is 166.1 K, and the gross cooling power is 3.83 W at 5.20 MPa. The temperature of the cooler increases with the rise of heat load, while the parasitic heat load decreases. The cold-end temperature is 186.0 K, then the parasitic heat load and the gross cooling power are respectively 3.17 W and 7.17 W at 5.20 MPa under the heat load's condition of 4 W. Comparing the refrigeration performance of nitrogen and argon, the cold-end temperature of nitrogen at 5.20 MPa is 235.7 K, which is close to that of argon at 2.98 MPa. Whereas the cooling time of nitrogen is slightly shorter than that of argon, and the cooling power is 3.10 W, higher than that of argon. In addition, this study provides new insight into increasing the cooling power and reducing the application cost of miniature coolers.
Given its configuration and operation conditions, the performance of a counter-flow microchannel heat exchanger (MCHX) is evaluated through detailed calculations. The fluids, both liquid water and air, are considered as continuum flow flowing in microchannels. The MCHX has 59 sheets, and each sheet has 48 microchannels. The microchannels for both fluids have the same cross section of 0.8mm×1mm and same length of 200mm. Log mean temperature difference method is adopted for this evaluation. Using appropriate equations, the properties of air-water vapor mixture are calculated based on that of the two components. Given the inlet temperature for liquid water(35℃) and air (170℃),the calculated outlet temperature for both fluids are 55.5℃ and 43.3℃, respectively. The results also show that the air at the outlet is saturated. The overall heat transfer coefficient reaches 100W/m2ꞏK, which is much higher than that of conventional heat exchanger with similar fluid combinations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.