Pulsating heat pipe (PHP) is a high efficiency heat transfer device and has unique advantages in cooling electronic apparatus with high heat flux in tiny space.With simple structure

it operates with complex internal rule.The variation of the thermal resistance changing with heating power and filling ratio and the characteristics in nature is analyzed.The dryout characteristic of the PHP is discussed.From experiments on the PHP with four working fluids including water

methanol

ethanol and acetone under different operation conditions

four conclusions can be derived. (1) There is a limitation of thermal resistance for the PHP phase-change convection heat transfer mechanism.And the limitation has little to do with the filling ratio. (2) For different working fluids and filling ratios without dryout phenomenon

the thermal resistances are almost the same under high heating power. (3) The dryout phenomenon only emerges in some of the individual pipes in the evaporation section periodically.When the heat load is further intensified

dryout will occur in more pipes in the evaporation section and last for a longer time

but the temperature will not increase rapidly so that the PHP will not be burned out. (4) Before valid oscillation starts

the experimental data show that the decrease of thermal resistance may slow down or change to increase first and then decrease

with an inflection point

which is different from the almost linear decrease described in literature.This work provides a reference for establishing theoretical model and understanding the heat-transfer of pulsating heat pipe.