Experimental Study on Closed-Loop Two-Phase Thermosyphon Devices for Cooling MCMs

Abstract

Thermosyphon cooling modules, to cool multichip modules (MCMs), were designed and tested. The cooling module consists of a cold plate with micro nned channels and a plate-type integrated condenser. A separate ow model was employed to predict the mass ux and the pressure drop in the channel of the cold plate. The local and average convective boiling heat transfer coef cients and the corresponding wall superheat were calculated using the Chen's correlation. Experiments were performed to nd out how the thermal performance of the cooling module was affected by the condenser size and the amount of charging uid. Great emphasis was placed on the transient characteristics of the cooling module. For an allowable temperature rise of 58°C on the surface of the heater, the cooling module can handle a heat ux of as much as 2.5 W/cm 2 . No boiling retardation was observed inside the cold plate, which resulted in smooth transition from the transient state to the steady one. It was also found that the appropriate size of the condenser and the adequate amount of charging liquid are crucial factors affecting the performance of a closed two-phase thermosyphon device.Switching systems in a broadband integrated services digital network (B-ISDN) will use the asynchronous transfer mode (ATM) and will have a throughput on the order of terabits per second. Correspondingly, the heat ux in a B-ISDN is one or two orders of magnitude higher than in conventional systems, and will reach 1-2 W/cm 2 , which will necessitate new packaging systems and ingenious cooling technology [1,2]. The multichip module (MCM) has been considered [3] an appropriate packaging design for B-ISDNs because its high packaging density will decrease signal propagation delay and reduce electromagnetic emission.The direct immersion cooling module [4] has been considered a promising method for such application because it removes a large amount of heat effectively. However, application of such a cooling method to communication systems is not an easy task because of dif culties in maintenance and reliability. As an alternative, ingeneous air-cooled thermosyphon modules [5,6] and indirect liquid-cooling thermosyphons [7,8] have been proposed for cooling high-density electronic packaging. However, it has been observed [9] that the 29

Thermal performance of a carbon fiber composite material heat sink in an FC-72 thermosyphon

“…The carbon-fiber heat sink tested here exhibits thermal performance below that of the carbon foam due to a smaller surface area resulting from the pin fin design. However, the thermal performance is improved when compared to the other traditional pin-fin evaporators [3][4][5][6][7] which dissipated a maximum of 2.5 W/cm 2 . Thus heat sink presented here dissipates up to 25% more flux than the previously studied pin fin designs.…”

“…Any effect of condenser temperature should be evident over this range. Heat flux at the evaporator ranged from 0.5 to 3.5 W/cm 2 , which was typical in the previous studies for pin-fin heat sinks at the evaporator surface [3][4][5][6][7].…”

“…The parameters considered in this study are evaporator power level, condenser operating temperature and fill ratio, which are the parameters seen to have an effect on thermosyphon performance in previous studies [3][4][5][6][7][8][9][10][11]. Based on the ranges studied in previous experiments as detailed in the introduction, the fill ratio was initially varied from 0.25 to 0.45 to investigate the effects of both flooding and starving the liquid levels.…”

“…Na et al [7] experimentally study an R-11 filled thermosyphon for indirect cooling of a multi-chip module at heat fluxes between 0.2 and 2.5 W/cm 2 . The average heat transfer coefficient was found to range from 900 to 2200 W/m 2 K. In this study it was found that higher fill ratios improve thermal performance.…”

“…While these studies [1][2][3][4][5][6][7] all use either flat plates or traditional pin-fin heat sinks at the evaporator, Klett and Trammell [8] perform a parametric investigation of a graphite foam evaporator in a thermosyphon with FC-72 and FC-87 as the working fluids. The effects of foam density, foam structure, working fluid and fill ratio are studied.…”