Thermal analysis of water-filled micro heat pipes of natural-convection water heat sink

Abstract

Based on the principles of mass, momentum, and energy conservations as well as the Young-Laplace capillary equation, a one-dimensional steady-state model of micro heat pipes (MHPs) of equilateral-triangle cross section has been constructed, with the incorporation of a natural convection heat sink surrounding the condenser section. Subsequently, the model is utilized to address some of the issues associated with a copper-water MHP whose condenser section is immersed in a nominally quiescent cooling water. The heat transport capacity derived in this study agrees well with existing experimental results. Moreover, four parameters – the heat load, the operating temperature, the temperature of the condenser coolant, and the average temperature of the evaporator section – have been identified as the key factors associated with the performance of an MHP, and a detailed investigation on their relationships has been carried out. For an MHP filled with a fixed amount of working fluid, an operation chart relating these parameters has been constructed. Moreover, it is shown that these parameters are not totally independent of each other, since, given any two of them, the remaining two can be determined using a set of two coupled, approximately linear algebraic equations.