Loop heat pipe (LHP) is a kind of heat transfer device whose operating principle is based on the evaporation and condensation of a working fluid

and uses the capillary pumping forces to ensure the fluid circulationA series of tests were performed with a miniature loop heat 〖HJ*3〗pipe (mLHP) with flat evaporator and a finandtube type condenserThe loop is made of pure copper with stainless mesh wick and with acetone as the working fluid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 mLHP at heat fluxes from 15 W·cm-2 to 4 W·cm-2.The amplitude and frequency of the fluctuations were very high at evaporator wall and evaporator inlet

and the temperature oscillations of other sections had a smaller amplitudeThe compensation chamber was found to be the most critical component of the mLHP

and its hydrodynamic state dictated the extent and characteristics of the temperature oscillations for the input heat loadThe heat leaks from the evaporator to the compensation chamber

the heat loss to the surrounding and the subcooled liquid temperature dictated 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 liquid charging ratio and tilt angle on the temperature oscillation were studied in detailWith the increase of charging ratio

the zone of heat load in which temperature oscillation occurred narrowed but the amplitude became larger. With the increase of tilt angle

the amplitude increased while the frequency decreased

and the limit of heat load at which temperature oscillation occurred increased.