Experimental investigation on temperature oscillation in a miniature loop heat pipe with flat evaporator

Abstract In this work, a series of experiments were conducted to investigate the effect of temperature oscillation on startup behavior and operating performance in a miniature LHP with flat evaporator of 8 mm thick. The evaporator with sintered copper powder wick is in series structure with compensation chamber and made of copper. Water is the working fluid. It is found that the LHP is able to start up at heat load of 15 W with temperature oscillation. And the oscillating frequency of temperature rises and amplitude decreases with increasing heat load. For the LHP in the present work, temperature oscillation is caused by insufficient driving force and phase distribution of working fluid in the compensation chamber under different heat load. The development of unstable operation in the LHP is the reflection of the re-distribution of working fluid in the loop while the hydrodynamic and thermal equilibrium of the loop is broken and re-built repeatedly. For specific heat load, high operating temperature can improve the operating stability of LHP due to large capillary force.