Novel condenser based cryogenic pulsating heat Pipe: Investigations on influence of geometrical parameters

Abstract

Pulsating heat pipes (PHPs) are becoming popular among passive cooling devices as a possible replacement for the thermal conductive links associated with cryocooler applications. To cool high-temperature superconductors, the need for a large cooling capacity cryocooler is rapidly increasing. The available literature studies show that the heat transfer capability of cryogenic PHP depends on the cryocooler's cooling power. Therefore, findings of a higher heat transport limit and optimal geometrical parameters for a cryogenic PHP remain unsolved. The present paper focuses on developing a novel cylindrical shell-type condenser (CSTC) to provide a high cooling load in a cryogenic PHP. Liquid nitrogen is used as a cryogen. The experiments are performed to study the influence of a number of turns (Single-Turn (ST), Two-Turn (TT)) and adiabatic length (60 mm, 120 mm) designated as ST-60, ST-120, TT-60 and TT-120 PHPs. The inner and outer diameters of PHPs are 1.3 mm and 3.2 mm, respectively. The filling ratio (FR) of cryogen is kept between 38 % and 95 %. The heat load varies from 1 W to 60 W with a bottom heating position. For a case of varying adiabatic length, the lowest thermal resistance increases by 24.78 % for ST-120 PHP compared to ST-60 PHP and 3.23 % for TT-120 PHP compared to TT-60 PHP. For a case of a number of turns, the lowest thermal resistance decreases by 36.57 % for TT-60 PHP compared to ST-60 PHP and 47.5 % for TT-120 PHP compared to ST-120 PHP. The maximum effective thermal conductivity (Keff) of 40,590 W/m-K is observed for an ST-120 PHP. A hybrid cooling technique is proposed with a combination of a novel CSTC and cryocooler to provide a high cooling load with a lower need for cryogen replenishment in the condenser section of a PHP device for an on-ground application.