Thermal Analysis and Flow Visualization of a Flat Loop Heat Pipe

Abstract

Thermal management is an important issue for electronic cooling application. Choosing an efficient cooling technique depends on thermal performance, reliability, manufacturing cost, and prospects for minimization of packaging cost. A loop heat pipe with a flat evaporator and a flat gap condenser was designed and developed to evaluate the loop performance for a range of heat load. During the study, the startup process and temperature profiles at different components of loop were compared at various heat loads. Heat transfer coefficients and the thermal resistances of the loop were also measured at these loads. In the evaporator, a disc shape copper wick was able to handle 100-watt heat load with the evaporator thermal resistance of 0.14Ԩ/ܹ and heat transfer coefficient of 14.114ܹ/݉ ଶ Ԩ. To visually investigate the startup process and component performance, main structure of loop heat pipe was fabricated inside acrylic plastic block. The startup process in the vapor line, the formation of bubble inside condenser and compensation chamber during the loop heat pipe operation were visualized and explained. The visualization process helps to understand the physical phenomenon of the complete heat loop in a single frame.