Study on the effect of condenser configuration of pulsating heat pipes for space applications

Abstract

In this study, the effect of condenser configuration on the thermal performance of pulsating heat pipes (PHPs) for space applications is experimentally investigated. The thermal performances of a single-condenser PHP and double-condenser PHP are compared under the constraints of the same evaporator and condenser areas. The PHPs are composed of a meandering channel with 30 turns and are made of a stainless-steel tube with the inner and outer diameters of 1.0 and 1.6 mm, respectively. R-134a is used as the working fluid, and the filling ratio is varied from 30 % to 60 %. Under various experimental conditions, the thermal performances of both single- and double-condenser PHPs are examined from two perspectives. First, the thermal resistances of the two PHPs are compared across a range of condenser temperatures from 10 to 30 degrees C and heat inputs from 0 to 700 W. According to the experimental observations, the double-condenser PHP exhibits a considerable reduction in thermal resistance, up to 55 % compared with the single-condenser PHP, across all the experimental conditions. Second, the operating ranges of the two PHPs are compared. For the single-condenser PHP, either an increase in the filling ratio or a decrease in the condenser temperature results in a narrower range of stable operation, with a maximum allowable heat input of approximately 200 W. On the other hand, the double-condenser PHP is mostly in the stable operating region regardless of the filling ratio or condenser temperature. Consequently, it exhibits an operating range approximately four times wider than that of the single-condenser PHP, indicating a significantly expanded range of stable operation. These improvements in thermal performance can be attributed to having the effects of doubling the number of evaporator-condenser pairs and halving the length between the evaporator and the condenser.