Fundamental Investigations for Very High Heat-Flux Innovative Operations of Milli-Meter Scale Flow Boilers

Michigan Technological University, Houghton MI

Investigators

Abstract

CBET-1402702 High heat flux removal is of critical importance in a number of key applications such as electronic cooling or data center cooling (where heat generated by electronic processors or components have to be rapidly dissipated to keep them working reliably). One of the most effective ways of removing heat is through a phase change process such as boiling in cooling channels integrated on the back side of the heat-generating device. In electronic applications, the heat is typically generated at the chip-level, and due to the small sizes, significant functionality and boiling efficiency problems arise due to the vapor blocking the channel, and instabilities in the channel. The proposed research will focus on methods that will overcome the efficiency issues by ensuring a thin continuously evaporating film on the heated surface. Successful development of these methods will ensure improved reliability of computer and electronic devices and enable denser packaging and smaller footprint. For the proposed study, high heat-flux capabilities are expected under externally imposed pulsations in the two phases (liquid and vapor). Thin and wavy boiling liquid films arise as a result of the pulsations, and cover the entire heat-exchange surface. Investigations will confirm if one can achieve high heat-flux values along the length of the flow boiler by a suitable adjustment of the mean quasi-steady film thickness profile (in the absence of pulsations) along with amplitude control of superposed waves (by controlling the amplitude of imposed pulsations). This is expected because the liquid film flow dynamics near the wave-troughs are dominated by the contact-line flow physics which causes the wave-troughs to "stick/dwell?" near the heat exchange surface. Therefore, under the proposed pulsatile operations, at most locations, the mean liquid film thickness will be significantly reduced and convection effects (in the liquid flow between the heat-exchange surface and the liquid-vapor interface) will be concurrently increased.