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.
Study on Thermal Performances of a Small Loop Heat Pipe
This paper describes thermal performance of a small loop heat pipe device in an atmospheric condition. A comprehensive test program including start-up, power step up, power cycle and low power tests was performed. The effects of gravity on start-up and heat transport capability were also evaluated. An analytical model for the loop was developed to predict and evaluate the steady state operating performance. The test results demonstrated the robustness of the LHP. The analytical results showed good agreement with the test results except at the low power region. The feasibility of loop temperature control through compensation chamber temperature control was also experimentally demonstrated.
Influence of pressure and fluidization velocity on the hydrodynamics of a fluidized bed containing horizontal tubes
Abstract An experimental investigation of the influence of horizontal tubes on the bubble behaviour and through-flow velocity of gas inside bubbles was carried out and the influence of pressure and fluidization velocity was studied. The visible bubble flow rate and the gas velocity through the bubbles were measured simultaneously in a pressurized fluidized bed, using capacitance and Pitot-static pressures probes respectively. Silica sand with a mean particle diameter of 0.7 mm was fluidized at pressures between 01. and 1.6 MPa, in a bed of 0.2 × 0.3 m cross-section. Six different horizontal tube configurations were used and comparisons were made with results obtained in the same bed operated without tubes. The results from the bed with tubes show that the influence of pressure and fluidization velocity is basically the same as in the bed without tubes; an increase in pressure and fluidization velocity increases the bubble activity. At low excess gas velocities, the influence of immersed tubes on the bubble behaviour is less pronounced than at high excess gas velocities. Measurements and visual observations show that a small tube pitch gives a more uniform distribution of the visible bubble flow over the bed cross-section. At a combination of high pressure, high excess gas velocity and a large tube pitch, a preferred bubble path was observed in the centre of the bed cross-section. The pressure probe measurements show that the through-flow velocity of gas inside the bubbles is in most cases higher when tubes are present in the bed. The through-flow velocity consistently decreases with increasing pressure in the bed without tubes. The tendency is largely the same at a low excess gas velocity when tubes are present, but at a high excess gas velocity the through-flow velocity first decreases and then increases as the pressure is increased.