Prediction of subcooled flow boiling local heat transfer coefficient in microchannel heatsinks

Abstract

This study aims to evaluate previous models that describe the average heat transfer coefficient (HTC) of subcooled flow boiling in microchannels and modify them to predict the local HTC. To enrich and extend the databases of these models, three-dimensional computational fluid dynamics simulations of HFE-7100, ethanol, and water in a wide range of heat fluxes were performed. The effect of the inlet degree of subcooling, or the difference between saturation and bulk fluid temperatures, on thermal performance is first investigated. Following that, the effect of the channel height-to-width ratio is investigated by examining four microchannels of different sections. Although decreasing the inlet subcooling tends to increase the overall HTC, it results in a lower maximum allowable heat flux due to the increase in bubble coverage of the bottom wall. A greater height-to-width ratio may improve the HTC, but there is an optimum ratio beyond which thermal performance degrades. Finally, the predictability of five models describing the average HTC of the subcooled flow boiling region is investigated, and adjusted correlations for accurate local HTC prediction are presented. A new correlation predicting the length of the onset of nucleate boiling is also demonstrated.

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Notes on contributors

Armin Beitollahi

Armin Beitollahi completed his M.Sc. in thermos-fluids at the school of Mechanical Engineering at the University of Tehran in 2021. His research interests are multiphase flows and applied computational fluid dynamics.

Amirmohammad Sattari

Amirmohammad Sattari is a Postdoctoral Fellow at the University of Tehran, Iran, School of Mechanical Engineering. He has a Ph.D. from the University of Tehran, Iran. His research interests are multiphase flow, microfluidics, drug delivery, and bubble dynamics. He has currently published 24 articles in peer-reviewed journals.

Pedram Hanafizadeh

Pedram Hanafizadeh is an Associate Professor in the School of Mechanical Engineering at the University of Tehran, Iran. He received his Ph.D. from the Sharif University of Technology, Iran. His research interests are multiphase flows, fluid mechanics, numerical simulations, and energy conversion.

Mehdi Ashjaee

Mehdi Ashjaee is a Professor of thermal-fluid science in the School of Mechanical Engineering at the University of Tehran, Iran. He received his Ph.D. in 1986 from the University of Wisconsin-Madison, USA. His research interests are forced and free convection heat transfer problems using interferometry and holography. He has published over 180 articles in well-recognized journals and proceedings.