Condensation heat transfer and pressure drop of refrigerant R-134a in a plate heat exchanger

An experimental refrigerant loop has been established in the present study to measure the condensation heat transfer coefficient h(r) and frictional p ressure drop Delta P-f of R-134a in a vertical plate heat exchanger. Two ve rtical counter flow channels were formed in the exchanger by three plates o f commercialized geometry with a corrugated sinusoidal shape of a chevron a ngle of 60 degrees. Downflow of the condensing R-134a in one channel releas es heat to the cold upflow of water in the other channel. The effects of th e refrigerant mass flux, average imposed heat flux, system pressure (satura ted temperature) and vapor quality of R-134a on the measured data were expl ored in detail. The results indicate that at a higher vapor quality the con densation heat transfer coefficient and pressure drop are significantly hig her. A rise in the refrigerant mass flux only causes a mild increase in the it, values h(r) most cases. The corresponding rise in the Delta P-f value is slightly larger. Furthermore, it is noted that the condensation heat tra nsfer is only slightly better for a higher average imposed heat flux. But t he associated rise in Delta P-f is larger. Finally? at a higher system pres sure the h(r) value is found to be slightly lower. But the effect of the sy stem pressure on Delta P-f is small. Correlations are also provided for the measured heat transfer coefficients and pressure drops in terms of the Nus selt number and friction factor, (C) 1998 Elsevier Science Ltd. All rights reserved.