Prediction of two-phase pressure drop in heat exchanger for mixed refrigerant Joule-Thomson cryocooler

Abstract

Abstract. The overall efficiency of a mixed refrigerant Joule-Thomson (MR J-T) cryocooler is governed by the performance of the recuperative heat exchanger. In the heat exchanger, the hot stream of the mixed refrigerant undergoes condensation at high pressure while the cold stream gets evaporated at low pressure. The pressure drop in the low pressure stream is crucial since it directly influences the achievable refrigeration temperature. However, experimental and theoretical studies related to two-phase pressure drop in mixtures at cryogenic temperatures, are limited. Therefore, the design of an efficient MR J-T cryocooler is a challenging task due to the lack of predictive tools.In the present work, the existing empirical correlations, which are commonly used for the prediction of pressure drop in the case of pure refrigerants, evaporating at near ambient conditions, are assessed for the mixed refrigerants. Experiments are carried out to measure the overall pressure drop in the evaporating cold stream of the tube-in-tube helically coiled heat exchanger. The predicted frictional pressure drop in the heat exchanger is compared with the experimental data. The suggested empirical correlations can be used to predict the hydraulic performance of the heat exchanger. IntroductionJoule-Thomson (J-T) cryocoolers are known for fast cool-down time, low cost and low vibrations at the cold end because of no moving parts in the cold section. The use of a refrigerant mixture of nitrogen-hydrocarbons as a working medium in these cryocoolers enhances their efficiency. Additionally, pressure requirements drastically get reduced up to 2 MPa in comparison to that of using a pure component as a working fluid, which allow the use of oil-lubricated compressors. However, the overall performance of such mixed refrigerant Joule-Thomson (MR J-T) cryocoolers greatly depends on the refrigerant mixture, heat exchanger and compressor. Numerous experimental and theoretical studies of MR J-T cryocoolers operating in the temperature range of 80-230 K have been reported in the literature [1][2][3][4]. These studies are mainly related to the optimization of mixtures used and the overall performance of the refrigeration systems. However, little work [5][6][7] is done on the performance analysis of the recuperative heat exchanger used in the MR J-T cryocooler, even though it plays a crucial role in its efficient operation. This is mainly due to the lack of the experimental data available, related to flow boiling/condensation heat transfer and pressure drop of mixed refrigerants at cryogenic temperatures. The refrigerant mixture undergoes boiling and condensation heat transfer simultaneously, in the counter-flow heat exchanger. The hydraulic diameter of the heat exchangers is

Recent advances in the applications of machine learning methods for heat exchanger modeling—a review

“…Pressure drop or pressure differential refers to the decrease in pressure that a fluid experiences as it flows through a conduit, valve, bend, heat exchanger, or other equipment. This decrease in pressure is due to factors such as frictional resistance, local resistance, or thermal effects (Ardhapurkar and Atrey, 2015). It is imperative to minimize the pressure drop across a heat exchanger (HX) because a reduced pressure drop directly translates to decreased pumping power and a subsequent reduction in the energy input required for the system in which the HX operates.…”