Session: 11-13-01 Fundamentals and Applications of Evaporation, Boiling and Condensation

Paper Number: 73527

Start Time: Wednesday, 10:45 AM

73527 - Three-Dimensional Numerical Study on the Flow and Heat Transfer in Wick of Loop Heat Pipe 

The 190 ~ 250 K loop heat pipes are widely used in space detection systems. They can not only meet the demand of high-efficiency thermal control of the optical systems, but also isolate the mechanical vibration and electromagnetic interference caused by the cryogenic refrigerator, which is used to provide the cooling capacity in the system. When the space detection devices need to be arranged compactly, loop heat pipes are highly advantageous due to their flexible thin-walled transmission pipelines. In addition, the loop heat pipe is a kind of passive heat transfer device with no moving parts, so it can operate for a long term with high stability. In the 230K temperature zone, the quality factor of propylene is higher than ethane and other working media. Evaporator is the core component of the loop heat pipe. The wick in it drives the liquid working medium by capillary force, which makes the liquid evaporate on the surface of the wick continuously. The liquid flow, heat transfer and phase change process of the working medium in the wick can significantly affect the performance of the loop heat pipe, and yet are still not fully understood.

In this paper, a three-dimensional model of a propylene loop heat pipe evaporator is developed using CFD method. The flow, heat transfer and phase change of propylene in a cylindrical evaporator is investigated numerically. In the model of the wick of the evaporator, both of the capillary force on the vapor-liquid interface and the flow resistance of the fluid in the porous medium are considered. Fluid-structure coupling heat transfer analysis is also involved in the evaporator model. The flow and thermal boundary conditions are determined according to the existing results of experiments. The shell of the evaporator is made of copper and the Sintered nickel power is used as the material of the wick, whose porosity is 0.6 and the average diameter of the porous structure is 5μm. The temperature, vapor-liquid phase and pressure distribution in the wick and vapor groove of the evaporator under 20 W, 30 W and 40 W input heating power are studied. The simulation results show good agreement with the experimental data. By introducing the capillary force at the two phase interface, this model can better describe the vapor-liquid distribution in the wick of the cylindrical evaporator. The results may provide the guidance for optimizing the structural parameters of the loop heat pipe evaporator.

Presenting Author: Bo Shao Shanghai Institute of Technical Physics of the Chinese Academy of Sciences

Authors:

Bo Shao Shanghai Institute of Technical Physics of the Chinese Academy of Sciences
Nanxi Li Shanghai Institute of Technical Physics of the Chinese Academy of Sciences
Yu Chen Shanghai Institute of Technical Physics of the Chinese Academy of Sciences
Deping Dong Shanghai Institute of Technical Physics of the Chinese Academy of Sciences