A heat transfer model of the simple loop pulsating heat pipe（PHP）was established to analyze the key influence factors for the thermal resistance and heat transfer rate of PHP.The results indicated that the thermal resistance of PHP included cooling thermal resistance and cycling thermal resistance.The velocity of cooling flow

cooling area

and the ratio of cooling area to heating area were the major factors affecting the cooling resistance

while the temperature of heat source and the charging ratio were the main factors affecting the cycling thermal resistance.The cooling temperature had less influence on thermal resistance.Heat transfer rate could be enhanced by the increase of cooling area

the ratio of cooling area to heating area

velocity of cooling flow

temperature of heat source

charging ratio

and reduction of cooling temperature.Enhancing the first three factors was the best way to increase heat transfer rate.The charging ratio varied from 10% to 80%

when the loop pulsating heat pipe was in the steady working condition

and the heat transfer rate increased a little as the charging ratio increased.