Fundamental issues, mechanisms and models of flow boiling heat transfer in microscale channels

Abstract

This paper presents state-of-the-art review on the fundamental and frontier research of flow boiling heat transfer, mechanisms and prediction methods including models and correlations for heat transfer in microscale channels. First, fundamental issues of current research on flow boiling in microscale channels are addressed. These mainly include the criteria for macroscale and microscale channels. Then, studies on flow boiling heat transfer behaviours and mechanisms in microscale channels are presented. Next, the available correlations and models of flow boiling

On the Phenomenal Mechanisms and Prediction Methods of Flow Boiling Heat Transfer in Microchannels

“…However, a universal agreement is not clearly established in the literature. Instead, there are various definitions on this issue, which are based on the engineering applications and bubble confinements as summarized by Cheng and Xia [2], Cheng and Mewes [5] and Cheng et al [8]. Just to give one definition here, based on engineering practice and application areas such as refrigeration industry in the small tonnage units, compact evaporators employed in automotive, aerospace, air separation and cryogenic industries, cooling elements in the field of microelectronics and micro-electro-mechanical-systems (MEMS), Kandlikar [3] defined the following ranges of hydraulic diameters Dh which are attributed to different channels: According to this definition, the distinction between small and conventional size channels is 3 mm.…”

“…These heat transfer mechanisms are commonly considered when developing flow boiling heat transfer correlations in conventional channels such as the Chen correlation [10] and others [11][12][13][14][15][16][17]. However, nearly all conventional flow boiling correlations have been found to be inadequate to predict the flow boiling heat transfer data in the microchannels [2,18]. On a general basis, although by chance they sometimes work for a particular data set, the failure of these methods to accurately predict the heat transfer coefficient in microchannels means that more complex flow boiling heat transfer mechanisms dominate the flow boiling processes in microchannels.…”

“…As a result of the enhanced thermal performance compared to other processes, better axial temperature uniformity, reduced coolant flow rates, and thus smaller pumping powers are obtained in flow boiling and two phase flow cooling technology. However, flow boiling heat transfer characteristics and mechanisms in microchannels are quite different from those in conventional channels [2][3][4][5][6][7]. The channel confinement has a significant on the flow boiling heat transfer characteristics and mechanisms.…”

“…Flow boiling in microchannels has become one of the "hottest" research topics in heat transfer as a highly efficient cooling technology for the past decades [1][2][3][4][5]. It has numerous advantages of high heat transfer performance, chip temperature uniformity, hot spots cooling capability, and more.…”

“…It has numerous advantages of high heat transfer performance, chip temperature uniformity, hot spots cooling capability, and more. For instance, the micro-electronics technology continues to develop with surprisingly rapidity and the thermal energy density of electronic devices to be dissipated is becoming much higher up to 300 W/cm 2 or even higher [6]. One possible solution is to use forced vaporization in micro-channels (e.g.…”