| Computational and experimental investigations of fluid flow and heat transfer aspects of loop heat pipes (LHPs) are presented in this thesis. The overall goal is to formulate and develop cost-effective mathematical models and numerical solution methods for computer simulations of LHPs. This work has five distinct parts.; First, a basic network thermofluid model of conventional LHPs operating under steady-state conditions is proposed, implemented, tested, and applied. It illustrates the main steps in the formulation of such models. The capabilities of this basic model are assessed by applying it to an LHP for which experimental results are available in the literature. The results show that this model is capable of at least qualitatively accurate predictions and could serve as a tool in preliminary designs of LHPs.; Second, experimental apparatus and procedures are designed and implemented for measurements of the following properties of sintered powder-metal porous plates that are used as wicks in LHPs: Porosity; maximum effective pore size; effective permeability; and effective thermal conductivity when saturated with a liquid (distilled water in this work). The aforementioned experimental apparatus and procedures are applied to two sintered powder-metal porous plates, one made of nickel 200 and the other of stainless steel 316, and the results are presented and discussed.; Third, an LHP with a flat (plate-type) evaporator and a fixed active mass of the working fluid (distilled water) is designed and constructed, and an experimental investigation of its steady-state operation is conducted. Full details of this LHP and the experimental setup and procedures are presented. The experimental results augment the available repertoire of experimental data on LHPs. They are used to test the predictions of the proposed network thermofluid model.; Fourth, an enhanced version of the aforementioned basic network thermofluid model is proposed and adapted for computer simulations of the above-mentioned LHP operating under steady-state conditions.; Fifth, results of experimental and computational investigations of the abovementioned LHP, operating with a stainless steel 316 wick and distilled water as the working fluid, are presented, compared, and discussed. The proposed network thermofluid model provides predictions that are within +/-10% of the experimental results. |
