Parametric Investigation Into the Effects of Pressure, Subcooling, Surface Augmentation and Choice of Coolant on Pool Boiling in the Design of Cooling Systems for High-Power-Density Electronic Chips

Abstract

A high power electronic chip was simulated experimentally to investigate upper cooling capabilities using a variety of pool boiling enhancement techniques. Parametric effects of system pressure, subcooling, surface augmentation, and choice of coolant on boiling heat transfer from a vertical 12.7 × 12.7 mm2 flat surface were examined. The two fluorocarbon coolants tested, FC-72 and FC-87, resulted in similar boiling curves, but FC-87 significantly reduced chip surface temperature for a given heat flux. Increasing pressure enhanced boiling performance and critical heat flux slightly. However, the significant increase in chip temperature, and the practical problems associated with packaging electronic hardware in a pressurized environment precluded pressurization as a viable enhancement option. Subcooling was very effective in increasing critical heat flux and significantly reducing bubble size and growth of the bubble boundary layer on the chip surface. Surface augmentation was also effective in enhancing critical heat flux; however, some surface geometries promoted noticeable temperature excursion at incipience.

Effects of pressure, orientation, and heater size on pool boiling of water with nanocoated heaters

“…This tends to decrease the number of active bubble nucleation sites and increases the wall superheat which allows bubbles to depart from the surface. This is further supported for various liquids by other researchers [16][17][18][19]. Various authors [14,16,17,[19][20][21][22] reported that CHF also shows an increasing trend with increasing pressure.…”

“…This is further supported for various liquids by other researchers [16][17][18][19]. Various authors [14,16,17,[19][20][21][22] reported that CHF also shows an increasing trend with increasing pressure. Mudawar and Anderson [19] reported that an increase in pressure results in higher values of CHF using water as the working fluid.…”

“…Various authors [14,16,17,[19][20][21][22] reported that CHF also shows an increasing trend with increasing pressure. Mudawar and Anderson [19] reported that an increase in pressure results in higher values of CHF using water as the working fluid. Kazakova [22] found that the CHF value continues to increase with pressure till 40% of the critical pressure of the fluid and decreases beyond that critical value.…”

Assessment of high-heat-flux thermal management schemes

“…Recent studies (see [5]) have demonstrated various means of enhancing the performance of thermosyphons including: 1) geometrically modifying the chip surface (surface enhancement), 2) subcooling the coolant to a temperature well below the boiling point, and 3) increasing coolant pressure.…”

“…They include micro-texturing the surface with cavities and features whose size and shape are configured relative to the contact angle and thermophysical properties of the coolant [3], [8]- [14]. A second form of surface enhancement is machining of mini-structures (e.g., mini-grooves and mini-studs) which both help sustain the bubble nucleation and increase the surface area available for boiling [3], [5], [15]. The third method of enhancement consists of bonding a relatively large extended surface onto the device surface for the purpose of greatly increasing the heat transfer area, provided the conduction resistance associated with the heat sink does not increase the device temperature appreciably [15], [16].…”