مکانیک هوافضا (Apr 2023)
Experimental Study of the Pressure Drop and Condensed Heat Transfer of R-406a Refrigerant in Tubes Equipped with Extended Surface of Twisted Fins in Different Steps and Lengths
Abstract
Having been developed in accordance with the Montreal Protocol, R134a has been proposed as a potential replacement for R12. In accordance with the Kyoto Protocol, the use of R134a, which has a significant global warming potential, must be restricted. It has been stated that there is no one refrigerant or combination available that can address both the ozone depletion potential (ODP) and the global warming potential (GWP) concerns at the same time. According to the research, the goal of this effort was to produce an environmentally friendly refrigerant combination with minimal ODP and GWP values that perform virtually identically to R12 in terms of performance. With extremely low ODP and GWP values, R406a has the potential to be a useful refrigerant. Experimental investigations conducted on R406a refrigerant have shown that it may be a viable replacement for R12. In this research, the pressure drop created by the torsion in the steam condensation of R-406a inside the horizontal tubes and also changes in the heat transfer coefficient are investigated experimentally. In each experiment, parameters such as mass flow, refrigerant temperature and pressure, and water at the inlet and outlet of the condensers were measured. Examination of the results for annular and torsional fins pipes, it was determined that heat transfer and pressure drop increase with the reduction of the pitch. The use of spirals increases the average heat transfer coefficient and pressure drop by about 47% and 220%, respectively, compared to the pipe without fins. Finally, using the results from the twisted tubes and based on the relationships that best match the experimental results related to the pressure drop, a new relationship for the pressure drop in the twisted tubes was obtained. The values calculated by it are in the range of approximately 15% of the experimental values.
