Investigations on two-phase heat exchanger for mixed refrigerant Joule-Thomson cryocooler

Abstract

The design of the recuperative heat exchanger used to pre-cool the refrigerant mixture prior to J-T expansion is crucial for the efficient operation of the mixed refrigerant JouleThomson (MR J-T) cryocooler. The multi-component non-azeotropic refrigerant mixture undergoes boiling and condensation heat transfer simultaneously in the heat exchanger. Therefore, it is important to analyze the performance of the heat exchanger in terms of temperature distribution with respect to the mixture of gases used.In the present work, temperature measurements are carried out at the ends of the heat exchanger for high pressure stream, while eight sensors are installed at equal distance along the length of heat exchanger to measure temperature of low pressure stream. The paper reports variation in heat transfer coefficient along the length of the heat exchanger. The variation is discussed with respect to temperature distribution across the length and changes in thermo-physical properties of the gas mixture.

Modelling and Parametric Analysis of Wire Finned Coiled Tube Heat Exchanger in a Small J-T Refrigerator

“…Details of the operating parameters for different mixtures are presented in Table 3. Ardhapurkar et al [2] in their earlier study used coiled tube-in-tube heat exchanger as the recuperative heat exchanger in the J-T refrigerator. The reason for such longer length for the heat exchanger of 15 m is due to the large temperature glide of the working fluids on both sides of the heat exchanger (typically 200 K).…”

“…Coiled tube heat exchangers are widely used in small J-T refrigerators (heat capacities are typically less than 10 W) due to simplicity in their construction, less space occupancy and low longitudinal heat conduction [1]. Ardhapurkar et al [2] conducted series of experiments on multiple tubes-in-tube heat exchanger. Based on the mixture composition they stated the performance of heat exchanger in terms of overall heat transfer coefficient along the length of heat exchanger.…”

An Identification of the Best Mixture Composition for the Joule-Thomson Refrigerator Operating at 90 K

“…Little [4] described a method to choose a mixture for LRS systems with more than four compositions with a temperature range of 130 to 150 K. Dobak et al [5] stated a method for the selection of mixture and its composition that are used in cryosurgical devices with a temperature range of 120 to 270 K. Keeping in view of cooling capacity of J-T Refrigerator, Boiarskii et al [6] stated two completely non similar objective functions to select an appropriate optimized mixture. Based up on the compressor suction and discharge pressure, Gong et al [7] proposed a complex optimization algorithm to select the optimized mixture composition in the range of 80 to 150 K. Ardhakapur et al [8] conducted experiments in a recuperative heat exchanger which is used to precook the refrigerated mixture used in the Joule-Thomson refrigerator. They analysed the temperature distribution along the length of the exchanger and changes in thermo physical properties of the gas mixture.…”