Evaluation of forced convective boiling heat transfer with layered parallel microchannels

Abstract

In this study, we experimentally evaluated heat transfer performance using a configuration of layered parallel microchannels, with a focus on the effect of refrigerant mass flow rate on heat transfer performance. HFC-245fa was used as a refrigerant owing to its chemical stability and appropriate saturation pressure for the design of the cooling system under actual conditions. Experimental results showed that heat transfer rate and heat transfer coefficient increased with increasing refrigerant mass flow rate under the same superheat. However, the maximum heat transfer coefficient reached a certain value even as the mass flow rate increased. Further, on comparing the experimental results with numerical ones performed in this study, it was confirmed that the heat transfer performance with the configuration of layered parallel microchannels depended on the thermal resistance between each layer. Furthermore, to realize the maximum potential of the heat sink with the layered parallel microchannels, it was important to prevent a decrease in wall superheat at the channels on the far side from the heat source. Eventually, in the series of experiments, a heat flux of 3.04×106 W/m2 and a heat transfer coefficient of 5.20×104 W/(m2∙K) were reached at a pressure drop of 48.4 kPa under a mass flow rate of 3.33×10-2 kg/s. This was achieved despite the use of a simple configuration for heat transfer enhancement and a refrigerant having poor latent heat dissipation.

Keywords

• boiling
• microchannel
• heat transfer enhancement
• fluorochemicals
• refrigerant
• phase change
• heat sink