Experimental investigation of a flat-plate closed-loop pulsating heat pipe

[+] Author and Article Information
Wessel Wits

Thales Netherlands, P.O. Box 42, 7550 GD Hengelo, Netherlands; Netherlands Aerospace Centre (NLR), P.O. Box 153, 8300 AD Emmeloord, Netherlands; Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands

Gerben Groeneveld

Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands

Henk Jan Van Gerner

Netherlands Aerospace Centre (NLR), P.O. Box 153, 8300 AD Emmeloord, Netherlands

1Corresponding author.

ASME doi:10.1115/1.4042367 History: Received September 11, 2018; Revised December 17, 2018


The thermal performance and operating modi of a flat-plate closed-loop Pulsating Heat Pipe (PHP) are experimentally observed. The PHP is manufactured through CNC milling and vacuum brazing of stainless steel 316L. Next to a plain closed-loop PHP also one that promotes fluid circulation through passive Tesla-type valves was developed. Each channel has a 2×2mm2 square cross section. In total, twente parallel channels fit within the 50×200mm2 effective area. During the experimental investigation, the power input was increased from 20W to 100W. Three working fluids were assessed: water, methanol and ammonia. The PHP was charged with a 40% filling ratio. Thermal resistances were obtained for different inclination angles. It was observed that the PHP operates well in vertical evaporator-down orientation, but not horizontally. Moreover, experiments show that the minimum operating orientation is between 15-30°. Two operating modi are observed, namely the thermosyphon modus, without excessive fluctuations, and the pulsating modus, in which both the temperature and pressure responses oscillate frequently and violently. Overall thermal resistances were determined as low as 0.15K/W (ammonia) up to 0.28 and 0.48K/W (water and methanol, respectively) at 100W power input in the vertical evaporator-down orientation. Infrared thermography was used to visualize the working fluid behaviour within the PHPs. Infrared observations correlated well with temperature and pressure measurements. The experimental results demonstrated that the developed flat-plate PHP design, suitable for high-volume production, is a promising candidate for electronics cooling applications.

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