Loop heat pipe (LHP) development by utilizing coherent porous silicon (CPS) wicks

Abstract

This paper introduces a theoretical model for a Loop Heat Pipe (LHP) utilizing a coherent porous silicon (CPS) wick. The paper investigates the effects of different parameters on the performance of the LHP such as evaporator temperature, condenser temperature, total mass charge, wick thickness, porosity, and pore size. A LHP is a two-phase device with extremely high effective thermal conductivity that uses capillary forces developed inside its wicked evaporator to pump a working fluid through a closed loop. The loop heat pipe is developed to efficiently transport heat that is generated by a highly localized concentrated heat source and then to discharge this heat to a convenient sink. This device is urgently needed to cool electronic components, especially in space applications. The LHP has been modeled utilizing the conservation equations and thermodynamic cycle. The loop heat pipe cycle is presented on a T-s diagram. A direct relation is developed between the ratio of heat going for evaporation as well as heat leaking to the compensation chamber.

Parametric analysis of loop heat pipe operation: a literature review

“…The operating principle of the LHP [1,33,35,36] is as follows. Under steady state conditions, for a heat input Q e supplied to the evaporator, liquid is vaporized, and the menisci formed at the liquid/vapour interface in the evaporator wick develop capillary forces to pump the liquid from the compensation chamber.…”

“…Due to the various designs of LHPs, these limitations have magnitudes and characteristics different from those of conventional heat pipes [32,36].…”

“…Currently, LHP miniaturization is in the forefront of an extensive research and development to provide cooling solutions to the high heat load/heat flux problem of advanced electronic packaging [20][21][22][23][24][25][26][27][28]. The constrained space of such applications requires to design specific LHPs.…”

Micromachined passive phase-change cooler for thermal management of chip-level electronics

“…In these systems, the microchannels have been generally fabricated by silicon (Si) etching technologies to use the capillary force of liquid coolants during the device operation. However, unexpected liquid-vapor interface oscillating [18], backward bubble flow [19], and dryout problems [20] occurred due to unstable capillary forces during the phase-change process, which have led to the development of continuous and reliable MEMS-based phase-change cooler to overcome dryout limitations.…”

“…The main cooling mechanism is to utilize phase-change of coolant, similar to the cooling process used in heat pipes. In conventional heat pipes, because the traveling vapor is in direct contact with turning liquid in the wick material, there is parasitic heat transfer from vapor to liquid during the circulation, which may cause oscillating vapor-liquid interface [18,19]. To prevent parasitic heat transfer, a physical (thermal) barrier (i.e., wick layer) between vapor and liquid channels was introduced in the proposed device.…”