Effect of Microchannels Dimensions on Flow Boiling Using R134a

Abstract

In this study, we look at the effects of microchannel dimensions of tooling such as channel width and depth on the flow boiling aspects of refrigerant R134a, an issue that has received growing academic interest in the context of small scale, high-performance thermal management of electronics, aerospace and automotive system. Due to their increased surface-area-volume ratios, microchannels provide better performance in terms of heat-dissipation and thus, a large amount of experimental data has been undertaken correspondingly; by using an engineered experimental system our research endeavors in constructing better heat-extraction coolant data sets including the heat-transfer coefficient (HTC), critical heat flux (CHF), pressure drop, and flow-regime dynamics in the boiling cycle. The experimental evidence shows that channels of reduced diameter improve nucleate boiling, due to the large interfacial surface and stable and enhanced nucleation of bubbles, but it increases the pressure losses through vapor barrier and flow disturbances. Conversely, deeper channels enhance CHF by increasing wetted area and flow state stabilization, but at the cost of the possibility of unreasonable addendum to hydraulic resistance with excessive ones. It has been observed by flow-regime transition relating to bubbly flow to annular flow based on geometry and mass-flux conditions. This evidence highlights the critical role of a well-organized maximization of width and depth in the design of the microchannels to attain an excellent performance in boiling. Finally, this study will provide information in the form of empirical data and theories that can be used to design effective microchannel heat sinks using R134a, which will contribute to thermal regulation in high-performance systems.