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.
Submillimeter-thick loop heat pipes fabricated using two-layer copper sheets for cooling electronic applications
Abstract A new submillimeter-thick loop heat pipe (LHP) fabricated using two copper sheets is proposed as a cooling solution for thermal management of electronics. The experimental investigation was conducted by measuring the temperature of each part of the surface of the thin LHPs for its heat input, to evaluate the heat transport characteristics of the LHPs discussed in this paper. Submillimeter LHPs with thicknesses of 0.6 and 0.4 mm were fabricated using chemical etching and diffusion bonding processes on two thin copper sheets. A design is exhibited that achieves efficient heat transfer under a variety of operating orientations with a thin LHP, by using a half-etching process on a thin copper sheet to form a grooved structure that generates capillary force. A thermal resistance of 0.09 K/W between the evaporator and the condenser is achieved at 5 W in the top heat orientation, using a nonwoven fabric consisting of copper fibers located inside the flow path of one of the copper sheets. Moreover, it is demonstrated that heat transport can be achieved up to a heat input amount of 7.5 W without orientation dependence for an ultrathin LHP of 0.4 mm thickness.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.