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Loop heat pipes (LHP) are passive thermal management systems widely used in electronics cooling, military applications, renewable energy, and spacecraft. These two-phase systems employ capillary forces instead of pumps to circulate the coolant. In these devices, the coolant evaporates and condenses in the evaporator and condenser, respectively. The condensed coolant liquid is driven toward the evaporator by capillary action in a wick structure located inside the evaporator. A mechanical pump can be added to the liquid line of the loop to reach the distributed heat loads and control the temperature to produce an isothermal surface. In this work, the porous wick of an evaporator in a mechanically pumped loop heat pipe was analyzed employing the Computational Fluid Dynamics (CFD) code ANSYS/Fluent. The Volume of Fluid (VOF) model in ANSYS/Fluent is modified using a User Defined Function (UDF) to calculate mass transfer between the liquid and vapor phases at the interface. This research focuses on effect of applied heat flux on the evaporator, liquid mass flow rate at the wick inlet, wick porosity, permeability, and material thermal conductivity, and value of gravitational acceleration on the overall performance of the system. The results illustrate effect of each parameter on overall system performance and flow patterns of two-phase working fluid inside the porous wick. Some design recommendations also are made to fabricate the wick of such a system for any precious thermal management application. |
