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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
INFLUENCE OF WORKING FLUID ON THERMAL PERFORMANCE OF THERMOSYPHONS FOR APPLICATION IN HIGH PRESSURE VACUUM TUBE SOLAR COLLECTORS
Submission Author:
Thiago Antonini Alves , PR , Brazil
Co-Authors:
Guilherme Antonio Bartmeyer, Victor Vaurek Dimbarre, Pedro Leineker Ochoski Machado, PAULO HENRIQUE DIAS DOS SANTOS, Thiago Antonini Alves
Presenter: Pedro Leineker Ochoski Machado
doi://10.26678/ABCM.ENCIT2020.CIT20-0621
Abstract
Solar collectors are devices that absorb solar radiation and transfer it to a flowing fluid in order to heat it. One of the ways to increase the efficiency of these devices consists in using thermosyphons. Thermosyphons are highly efficient heat transfer devices which use latent heat of vaporization to transport high amounts of energy in the form of heat with a small temperature gradient. These devices consist basically in an evacuated metallic tube filled with a working fluid. Heat is absorbed in the evaporator region, generating steam from the working fluid. When the steam reaches the condenser region, heat is dissipated to the environment, condensing the steam that returns to the evaporator at the liquid state. In this work, different thermosyphons with three different working fluids (acetone, methanol, and distilled water) were built and tested. The evaporator and the adiabatic section have an outer diameter of 8.33mm and lengths of 1,600mm and 40mm, respectively. The condenser has an outer diameter of 13.40mm and a length of 35mm. The filling ratio used was 50% of the evaporator’s volume. Tests were carried out discharging heat at the evaporator due to Joule’s effect using a resistive tape and a power supply, while water flows at the condenser absorbing heat from it. Three different flow rates of water were used: 0.50, 0.75, and 1.00 L/min. Thermocouples were placed along the devices in order to obtain temperature data. The thermal analysis was based in temperature distribution, thermal resistance, and thermal efficiency. Acetone was found out as the working fluid with best performance along the three working fluids tested. Concerning the influence of the flow rate of water, higher flow rates equals lower temperatures along the devices and higher thermal efficiencies.
Keywords
Thermosyphon, heat pipe, Heat transfer, Solar Collector
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