R-431A افزايش انتقال حرارت در چگالش اجباري بخار

Heat Transfer Enhancement During Forced Condensation of R-134 a Vapor

In the present study, enhancement of heat transfer during condensation of R-134a inside horizontal coiled wire inserted tubes has been investigated experimentally. Test condenser was a double pipe counter-flow water cooled heat exchanger which refrigerant flows inside the internal tube, while water flows in the annulus. Coiled wires with different wire diameters and coil pitches were utilized in full length of test condenser. It is found that the use of helically coiled wire increased the condensing heat transfer by as much as 85 percent above the plain tube values on a nominal area basis. Influence of variety of parameters such as vapor quality and coiled wire geometry on the heat transfer augmentation was also investigated. A correlation for the prediction of heat transfer coefficients inside the coiled wire inserted tubes was developed by utilizing the gained results for the rough tubes, on the basis of Boyko and Kruzhilin (1967) correlation.