Mechanism Investigation On Flow And Heat Transfer Of Capillary Pumped Loop

Capillary Pumped Loops (CPLs) and Loop Heat Pipes (LHPs) are two-phase heat transport devices which utilize the capillary forces developed in evaporator wick to drive the working fluid. They are capable of transferring large heat loads over long distances with small temperature differentials. Both CPLs and LHPs are considered to be most promising thermal control devices of spacecrafts in the future.The purpose of this thesis is to investigate operational mechanisms of the evaporator and the whole system, optimize the design and test the operation characteristics of small-scale CPLs and LHPs. The investigation is focused on the following aspects.1. Numerical investigation of the porous wick and evaporatorA 2D generalized mathematical model is given, which includes coupled heat and mass transfer process in the porous wick. With this model, the temperature field, liquid-vapor front and velocity field could be easily simulated, which reveals the physical operational mechanisms of the porous wick. A 3D numerical model of the evaporator is developed with software FLUENT. The heat and mass transfer processes in the evaporator with different structure are calculated and discussed. The numerical results will guide the evaporator design of CPLs and LHPs.2. Analytical investigation of CPL and LHP systemA mathematical model is proposed to predict the steady-state performance characteristics of the LHP. Some factors of affecting the operational temperature, such as temperature of heat sink, temperature of ambient and adverse height, are included.A transient model is developed to predict the thermal and dynamic behavior of a CPL. This model can be used to explain the start-up process failure and the evaporator depriming when abrupt change of heat load. It also indicates that the possible temperature oscillations in the reservoir are disadvantageous for the stabilization of CPL.3. Development of high performance sintered wicks for CPLs and LHPsThe slip casting and cold pressing technique are used to develop the sintered wicks of a CPL and a LHP. The influences of different sintering parameters including density of the blank, sintering temperature and sintering time on the pore size, porosity, mechanical strength and distortion of the sintered wick are analyzed. Their electronic photographs (TEM) and the test results reveals that the sintered wicks have excellent properties with the...