Experimental heat transfer analysis of a cryogenic nitrogen pulsating heat Pipe at various liquid fill ratios. (5th February 2018)

• Record Type: Journal Article
• Authors: Fonseca, Luis Diego; Miller, Franklin; Pfotenhauer, John
• Is Part Of: Applied thermal engineering. Volume 130(2018)
• Page Start: 343
• Page End: 353
• Publication Date: 2018-02-05
• Subjects: Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2017.11.029
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: A nitrogen based PHP has been operated at temperatures between 77 K and 80 K. Various fill ratios below 40% and heat loads below 4.5 W have been applied. A minimum startup heat load of 2 W is required to operate the PHP successfully. Results show a maximum thermal conductivity of 70 kW/m/K at a fill ratio of 20%. Abstract: The experimental results of extensive testing of a cryogenic Pulsating Heat Pipe (PHP) using nitrogen as the working fluid operating between 77 K and 80 K is presented. Fifty-two different test runs were analyzed over a range of different fill ratios, heater input powers, and orientations in order to map thermal performance as a function of the system operating parameters. The temperature difference between the evaporator and condenser section were obtained using platinum resistance thermometers (PRTs), and a pressure transducer was used to record the fluid's pressure oscillations. As opposed to other N2 pulsating heat pipes which use less than 16 parallel tubes, this experimental PHP consists of 40 parallel tubes. The PHP was operated at different liquid fill ratios ranging between 10% and 40% and heat loads between 1 W to 4.5 W. Results show that the PHP's temperature difference between section are small and resulted in high effective thermal conductivities up to 70, 000 W/m/K at fill ratios around 20%. Also, it was shown the PHP stopped oscillating at heat loads below 1.5 W but operated successfully above 2 W. Results from experiments conducted in both horizontal and vertical orientations show that gravity has a significant effect on the thermal performance of the PHP even with a high number of turns.