Experimental study on thermal performance of loop heat pipes with flat evaporator for LSI package
Thermal performance of a loop heat pipe (LHP) equipped with a flat evaporator and a compensation chamber integrated onto the evaporator and separated from the evaporator was experimentally investigated. The heat leak in the flat evaporator is a critical problem as it results in the degradation of the heat transport characteristics of the LHP. In this paper, the heat leak quantity during the steady-state operation of the LHP was calculated by carrying out a thermal energy balance analysis for the flat evaporator. From the results, the heat conduction along the case sidewall of the evaporator dominated the heat leak on the evaporator, and it was found that the heat leak from the heat source to the compensation chamber decreased to 5% or less of the applied input power due to the reduced heat conduction of the evaporator casing.
Mathematical modeling of loop heat pipes and experimental validation
A mathematical model to calculate the steady-state performance of a loop heat pipe (LHP) is presented. The mathematical model is based on the steady-state energy conservation equations and the pressure drop calculations along the fluid path in the LHP. The LHP operating temperature is calculated as a function of the applied power at a given LHP condition. The beat exchange between each component of the LHP and the surroundings is taken into account. Both convection and radiation environments are modeled. Experimental validation of the model is attempted by using two different LHP designs. The validity of the mathematical model is investigated for different sink temperatures and elevations. The comparison of the calculations and experimental results showed good agreement (within 5% ). The proposed method proved to be a useful tool for reliable prediction of the steady-state performance characteristics of the LHP.
Testing of a Miniature Loop Heat Pipe Using a Thermal Electrical Cooler for Temperature Control
This paper describes the design and testing of a miniature LHP having a 7 mm O.D. evaporator with an integral CC. The vapor line and liquid line are made of 1.6mm stainless steel tubing. The evaporator and the CC are connected on the outer surface by a copper strap and a thermoelectric (TEC) is installed on the strap. The TEC is used to control the CC temperature by applying an electrical current for heating or cooling. Tests performed in ambient included start-up, power cycle, sink temperature cycle, and CC temperature control using TEC. The LHP demonstrated very robust operation in all tests where the heat load varied between 0.5W and 1OOW, and the sink temperature varied between 243K and 293K. The heat leak from the evaporator to the CC was extremely small. The TEC was able to control the CC temperature within +/-0.3K under all test conditions, and the required control heater power was less than 1W.