Experimental investigation and regression analysis on the characteristics of the JT refrigerator operating with natural refrigerant mixtures

Abstract

This paper presents the results of the analysis of the experimental characteristics of the closed-cycle Joule-Thomson (JT) refrigerator operating on a nitrogen-hydrocarbon refrigerant mixture. Designing such energy-efficient refrigeration machines involves the calculation and experimental determination of the optimal values of the “charge” composition of the mixture components. The design process must take into account the change in the “circulating” composition of the mixture components. In the paper, we present the results of regression analysis of the “circulating” composition of the mixture components of a JT low-performance refrigerator (compressor volumetric flow rate less than 25 m3/h). Such refrigerators can be used for thermostatting objects at the temperatures down to −160 °C. The results are given in the form of relationships for specific refrigeration capacity and a number of efficiency indicators. In the considered component concentration range, the relative root-mean-square regression error was less than 12.6 %. Finally, we determined the optimal concentrations of the mixture components of the JT refrigerator having a compressor with a volumetric flow rate of 4.36 m3/h which corresponds to the maximum value of specific refrigerating capacity Qt/Ve [19,87 W/(m3/h)] at the temperature of the evaporator inlet of −150 °C. The results of approbation the proposed regression method on a prototype low-temperature freezer based on a JT refrigerator operating with MMR and the limits of applicability of the developed regression models are determined. These relationships provide valuable insights for designing stock-produced devices of varying standard sizes, reducing development time and cost while leveraging comparable operating cycles and working body compositions.