Influence of the Refrigerant Charge on the Heat Transfer Performance for a Closed-Loop Spray Cooling System

Nianyong Zhou,Haoping Peng,Yixing Guo,Hao Feng,Yu Wang,Yun Lei,Song Deng,Wenbo Liu

doi:10.3390/en14227588

Abstract

With the rapid increase of heat flux and demand for miniaturization of electronic equipment, the traditional heat conduction and convective heat transfer methods could not meet the needs. Therefore, the spray cooling experiment was carried out to obtain the basic heat transfer and cooling process. In this experiment, the spray cooling system was set up to investigate the influence of refrigerant charge on heat transfer performance in steady-state, dynamic heating, and dissipating processes. In a steady-state, the heat transfer coefficient increased with the rise of the refrigerant charge. In the dynamic dissipating process, both heat flux and heat transfer coefficient decreased rapidly after the critical heat flux, and the surface temperature drop point of each refrigerant charge was presented. The optimum refrigerant charge was provided considering the cooling parameters and the system operating performance. When the refrigerant operating pressure was 0.5 MPa, the spray cooling process presented with the higher heat flux, heat transfer coefficient, and cooling efficiency in this experiment. Meanwhile, the suitable surface temperature drop point and more gentle heat flux curves in the nucleate boiling region were obtained. The research results will contribute to the spray cooling system design, which should be operated before departure from the nucleate boiling point for avoiding cooling failure.

Highlights

As the increasing requirements in severe integration and miniaturization of electronic equipment, especially in the fields of advanced radar, high-performance laser weapons, and others, the conventional heat transfer methods such as simple single-phase convective could not contain the demand
The results showed that secondary nucleation is the main influence of spray cooling
The results showed that the chamber pressure was the main influence on the critical heat flux

Summary

Introduction

As the increasing requirements in severe integration and miniaturization of electronic equipment, especially in the fields of advanced radar, high-performance laser weapons, and others, the conventional heat transfer methods such as simple single-phase convective could not contain the demand. Introducing reliable and efficient cooling technology has become urgent work. Spray cooling technology casually attracts many researchers because of various heat transfer processes including evaporation, boiling, and convection heat transfer. Due to its higher heat transfer coefficient, better surface temperature uniformity, smaller heat change temperature difference [1,2,3], spray cooling is considered an effective technology in the field of great heat flux dissipation. The heat transfer mechanism of spray cooling involves complex multiphase flow. Researchers generally believe that spray cooling includes droplet impact, surface erosion, liquid film evaporation, and boiling process [4]

Methods

Results

Conclusion