Investigation of instability on loop heat pipe with flat evaporator

Abstract

Loop heat pipes (LHPs) are heat transfer devices whose operating principle are based on the evaporation and condensation of a working fluid, using the capillary pumping forces to ensure the fluid circulation. A series of tests have been carried out with a loop heat pipe (LHP) with flat evaporator and a fin-and-tube type condenser. At some low heat loads, temperature oscillations were observed throughout the loop. Detailed study was conducted on the characteristics of temperature oscillation of the flat LHP at various heat loads. It is expected that the compensation chamber is the most critical component of the LHP; its hydrodynamic state dictates the extent and the characteristics of the temperature oscillations. The heat leakage from the evaporator to the compensation chamber, the heat loss to ambient and the subcooled liquid temperature dictate the vapor condition inside the compensation chamber, and the rate of vapor growth or dissipation dictated the nature of the temperature oscillation. The effects of different working fluid to the temperature oscillations were studied in detail.