A pulsating heat pipe embedded radiator: Thermal-vacuum characterisation in the pre-cryogenic temperature range for space applications

Abstract

The use of Pulsating Heat Pipes (PHPs) in the space field is still an open issue because of the lack of data obtained during actual operation in relevant environment. A considerable amount of data is available in the literature on the thermal response of PHPs to a variable gravity condition and on the operation in the cryogenic field but in both cases the heat load at the condenser is rejected by convection to a constant temperature sink. On the other hand, barely any work in the PHP's literature deals with thermal radiation to a low temperature sink as only heat transfer mode. The present work attempts to fill the gap by testing a PHP radiator (16 turns, 1.1 mm inner diameter, 50% filled with FC-72 at 293K) in thermo-vacuum conditions in horizontal orientation at different heat loads and different environment (chamber) temperature. Fluid pressure measurements coupled with the frequency analysis characterised the effect of the cold source temperature on the device operational limits and efficiency. Results show that the device thermal performance in the radiative configuration is mostly affected by the lower operating temperatures needed to obtain a sensible heat rejection, rather than the heat transfer mode itself. The decrease of the environment temperature shortens the operational heat load range: the start-up occurs at higher heat input levels while the thermal crisis occurs at lower heat loads. The frequency analysis reveals that the equivalent thermal resistance is positively affected by higher values of the dominant frequency for all the cases.

Micro-Channel Oscillating Heat Pipe Energy Conversion Approach of Battery Heat Dissipation Improvement: A Review

“…The application of PHP in space had made great progress in recent years. Radiation PHP can be used for space applications requires an appropriate amount of heat input to start working at a lower operating temperature [89]. Iwata et al [90] tested a metal flexible PHP of the spacecraft.…”

Are Local Heat Transfer Quantities Useful for Predicting the Working Behavior of Different Pulsating Heat Pipe Layouts? A Comparative Study

“…PHP heat transfer performance is usually studied in terms of thermal characterizations, i.e., by evaluating equivalent thermal resistances under different operating conditions, including varying working fluid, the heat load to the evaporator, orientation, and condenser temperature [7][8][9][10][11]. Such an approach has been proven to be extremely suitable and effective from an application standpoint, i.e., when specific applications are considered, spanning from thermal management of batteries and electronic equipment to heat recovery applications and the cooling of foldable systems in both standard and microgravity conditions [12][13][14]. Nonetheless, the effectiveness of equivalent thermal resistance in terms of overall generalization of the working behavior is extremely controversial.…”