Performance characteristics of direct contact refrigeration system based on phase change materials and different refrigerants

Abstract

• Direct contact refrigeration system is built to improve system efficiency. • The problem of nozzle ice blockage is solved with phase change material. • COP of the system is 6.23 by using 35 wt% TBAB. In conventional ice storage refrigeration systems, the evaporator copper tube is immersed in a cold storage tank. Therefore, the thickness of the ice layer increases, the thermal conductivity of the evaporator decreases, resulting in a decrease in the system efficiency. To improve the efficiency of the refrigeration system, a new type of direct contact refrigeration system is designed and developed in this study. The direct contact between the refrigerant and water causes ice blockage in the nozzles and pipes. This is a common problem in direct contact refrigeration systems, and therefore, it is necessary to solve this problem. Four types of working media (R22, R134a, R410A, and HR223) are used to solve the problem of ice blockage in nozzles, and the impact on the system performance is discussed. The results showed that the working medium possesses a large latent heat of phase change, resulting in high system efficiency, however, and ice blockage still exists in the nozzles; the maximum efficiency of the system is 1.68. Water is replaced by phase change material (PCM), and the material is used for heat exchange with the refrigerant. The PCM is tetrabutylammonium bromide hydrate (TBAB), and the performance of TBAB with five mass fraction (25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt%) in the system is analysed. The results indicated that the refrigeration system with TBAB can solve the problem of ice blockage in nozzles. In addition, based on the experimental results, the coefficient of performance (COP) of the refrigeration system with TBAB concentration of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% is 3.11, 4.55, 6.23, 4.83, and 4.46, respectively. A series of experiments demonstrate that TBAB of 35 wt% exhibited the best performance in the direct contact refrigeration system. This paper presents a novel and innovative approach to solve the problems of ice blockage in direct contact refrigeration systems to improve system efficiency.