The MEMS Loop Heat Pipe Based on Coherent Porous Silicon — The Modified System Test Structure

Abstract

The previous papers presented at STAIF 2002 and STAIF 2003 discussed the design, fabrication and characterization of the evaporator section and the initial test cell of a planar MEMS loop heat pipe based upon coherent porous silicon or "CPS" technology. The potentially revolutionary advantage of CPS technology is that it is planar and allows for pores or capillaries of absolutely uniform diameter. Coherent porous silicon can be mass-produced by various MEMS fabrication techniques. The preliminary experiments made with the original test structure exhibited the desired temperature and pressure differences, but these differences were extremely small and oscillatory. This paper describes modifications made to the initial test cell design, which were intended to improve its evacuated, closed loop performance. Included among these changes were the redesign of the compensation chamber and condenser, an increase in the porosity of the coherent porous silicon wick, the fabrication of silicon top "hot" plates with an increased depth of the vapor reservoir and the integration of metal resistive heater elements onto the backside of the top plates to simulate the input heat. Some changes were made in the test sequence to produce more discernable differences in temperatures and pressures. The most recent results of the tests made with the modified system will be presented.

MEMS-Based Micro-heat Pipes

“…In addition to MEMS-based micro-grooved heat pipes, some other mini-or micro-scale heat pipes, such as capillary pumped loops (CPLs) [60][61][62][63][64], loop heat pipes (LHPs) [65][66][67][68][69], oscillating heat pipes (OHPs) [70][71][72][73][74][75], and vapor chambers (VCs) [76][77][78][79][80] as shown Figure 13, were also successfully constructed on silicon substrates by means of micro-fabrication technique recent years and became two-phase passive micro-coolers for electronic cooling. Similar to MEMS-based micro-grooved heat pipes, these novel MEMS-based MHPs could be considered as small versions of corresponding conventional prototypes and work at the related mechanism.…”