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Article

Experimental Study on the Stability and Transient Behavior of a Closed-Loop Two-Phase Thermosyphon (CLTPT) Charged with NOVEC 649

1
Centro de Investigación en Tecnologías Energía y Procesos Industriales (CINTECX), Universidade de Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain
2
Grupo de Tecnología Energética (GTE), Universidade de Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain
*
Author to whom correspondence should be addressed.
Academic Editor: Antonio Rosato
Energies 2021, 14(23), 7920; https://doi.org/10.3390/en14237920
Received: 25 October 2021 / Revised: 20 November 2021 / Accepted: 23 November 2021 / Published: 25 November 2021
Currently, the growing need for efficient refrigeration resources in the industrial sector has led to an increasing interest in finding technologies with a higher heat removal potential and better cooling performance. Along these lines, two-phase liquid cooling appears to be a very interesting solution, with the CLTPT (closed-loop two-phase thermosyphon) being one of the leading alternatives. Most works in the scientific literature study loop thermosyphons that work in flow boiling conditions in steady state. The present paper analyzes the transient thermal behavior of a pool boiling CLTPT gravitational channel as a passive cooling system using NOVEC 649 as working fluid. The evaporator works with two submerged cylindrical heaters that represent different heat sources located in different positions. The initial transient behavior and consequent instabilities of a laboratory-scale facility were studied, followed by a stability analysis for various power inputs. Parameters such as temperature and pressure along the experimental setup were monitored, and the effects of internal pressure and room conditions were also tested. The results show some instabilities in the process to start the flow circulation and a relative stability and quick adaptation to changes when circulation is reached. The temperature in the evaporator chamber was highly homogeneous during the whole process; however, the temperature changes in the riser and the loop top were delayed with respect to the evaporator zone. The analysis shows several pressure and temperature raises before the vapor flux reaches the condenser. When the flow circulation is established, the system becomes highly stable and thermally homogeneous, decreasing the thermal resistance when increasing the power input. The stability analysis also showed that, when the system reaches the steady state, the changes in the power input produce a transient increase in the pressure and temperature of the fluid, followed by a quick decrease of the previous steady state values. The heat transfer analysis in the evaporator shows a higher heat flux on the upper heater caused by the buoyancy flow that rises from the lower heater. It was also observed that the lower heater reaches the CHF point with a lower heat flux. View Full-Text
Keywords: cooling; heat transfer; pool boiling; transient behavior; system stability; thermosyphon; NOVEC; temperatures evolution cooling; heat transfer; pool boiling; transient behavior; system stability; thermosyphon; NOVEC; temperatures evolution
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MDPI and ACS Style

Larrañaga, A.; Gómez, M.A.; Patiño, D.; Porteiro, J. Experimental Study on the Stability and Transient Behavior of a Closed-Loop Two-Phase Thermosyphon (CLTPT) Charged with NOVEC 649. Energies 2021, 14, 7920. https://doi.org/10.3390/en14237920

AMA Style

Larrañaga A, Gómez MA, Patiño D, Porteiro J. Experimental Study on the Stability and Transient Behavior of a Closed-Loop Two-Phase Thermosyphon (CLTPT) Charged with NOVEC 649. Energies. 2021; 14(23):7920. https://doi.org/10.3390/en14237920

Chicago/Turabian Style

Larrañaga, Ana, Miguel A. Gómez, David Patiño, and Jacobo Porteiro. 2021. "Experimental Study on the Stability and Transient Behavior of a Closed-Loop Two-Phase Thermosyphon (CLTPT) Charged with NOVEC 649" Energies 14, no. 23: 7920. https://doi.org/10.3390/en14237920

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