Spray cooling system for high power electronic cooling

• Main Author: Boh, Yuerong
• Other Authors: Wong Teck Neng
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/76304
• Institution: Nanyang Technological University

Spray cooling has been gaining popularity for high power electronics cooling despite little has been known about it. This technique is effective in dissipating a heat flux in the order of a few hundred Watts per centimetre square. In this study, a high power multi-nozzle closed loop refrigeration-based spray cooling system was engaged to investigate the operating and performance characteristics of a two spray chambers connected in-parallel configuration. The surface of copper heated block on which spray impinges were modified to pin fins of dimensions 0.5mm x 0.5mm x 1mm in one of the two spray chambers while plain smooth surface was used in another chamber. The area of interest for cooling is 233mm x 160mm with an array of 54 spray nozzles using refrigerant R134a as the working fluid. Results from the investigation on single chamber in operation displayed a strong correlation between the mean surface temperature and chamber pressure. An increase in compressor speed lowers the chamber pressure and leads to a decrease in the mean surface temperature at a fixed heat load. A strong dependency was also found between the chamber pressure and the heat load applied across the chambers from investigation conducted on two chambers operation in parallel. The chamber pressures of both chambers can be controlled by varying the heat load of only one chamber. A decrease in the heat load applied will lead to a decrease in both chamber pressures. The mean surface temperatures of both chambers were lower when the compressor was running at higher speed. Single phase flow is preferred for efficient spray cooling and investigation conducted on the system found that the lowest compressor speed where two phase R134a mixture first occurred in spray supply line was found to be 23.5Hz when the heat load applied is below 7kW in total on both the spray chambers.