Experimental study of ethane pulsating heat pipe with varying evaporator lengths based on pulse tube refrigerator

Abstract

The study aims to investigate how the evaporator length affects the thermal performance of ethane pulsating heat pipe (PHP). It is also expected to offer an approach for further practical application. The experimental apparatus is designed with varying evaporator lengths, ranging from 40 to 240 mm, and the condenser length is kept at 40 mm. The facility measures 440 mm long and has a 2 mm inner diameter. The experiment is carried out by changing the working temperatures from −100 to −20 °C and the filling ratios from 40 to 60% with different heating inputs. A thorough analysis of the temperature oscillation and heat transfer performance of the PHP with different evaporator lengths is presented. Effective thermal conductivity is introduced to further evaluate the effect of the prolonged evaporator on the performance of the PHP. The influence of the working temperature on the selection of the evaporator length is explored. The optimal filling ratios with different working conditions are provided. Experiments confirm that extending the evaporator length stabilizes the evaporator temperature and generates a decrease in thermal resistance. The most stable operation of the PHP is achieved when the evaporator is 120 mm long. The thermal performance deteriorates as the working temperature decreases. The optimal working temperature occurs at −40 °C. The increment of the filling ratio enhances the performance of the PHP and is conducive to the lower working temperature.