| This dissertation addresses the modeling and characterization of a novel MEMS-based flat Micro Loop Heat Pipe (MLHP). The MLHP is proposed to be used in regulating the surface temperature of the ever-advancing state-of-the-art high power electronic devices and for other space or terrestrial thermal management purposes. MLHP is a micro scale two-phase heat transport device derived from heat pipes which consists of an evaporator with microgrooves, a compensation chamber, a condenser, and liquid and vapor lines. Numerical models were developed to simulate and optimize the flat-shape MLHP for various applied heat and operating temperatures under steady state condition. For most electronics, the maximum working temperature is an important design factor; therefore a closer estimation of surface temperature of the heat source (the electronic device) is crucial. This was performed in the model for various geometrical dimensions and working fluids as a function of the applied heat load. In these models, a typical evaporative heat transfer coefficient was assumed. In an upgraded version of the model, the principles of thin film evaporation were utilized in a submodel to predict the evaporative heat transfer coefficient in the grooves structures. This capability resulted in a self-sufficient model. To the extent of the available computational resources, the design of the MLHP was improved by evaluating the effects of the geometric feature variations while taking into account the fabrication limitations.; The final model was capable of predicting the heat removal capability, surface temperature, and local and average heat transfer coefficients in the evaporator of a working device at various applied heat loads. The results indicated that extremely high cross-sectionally averaged evaporative heat transfer coefficients can he achieved. The modeling results were verified by comparison to available experimental data. It was shown, in a separate study that the heat transfer coefficient, the contact angle of the meniscus, and the meniscus radius along the groove are non-uniform for uniform input heat fluxes but can be assumed almost uniform for most of the similar applications. |
