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

Abstract

An experimental refrigerant loop has been established in the present study to measure the condensation heat transfer coefficient h r and frictional pressure drop Δ P f of R-134a in a vertical plate heat exchanger. Two vertical counter flow channels were formed in the exchanger by three plates of commercialized geometry with a corrugated sinusoidal shape of a chevron angle of 60°. Downflow of the condensing R-134a in one channel releases heat to the cold upflow of water in the other channel. The effects of the refrigerant mass flux, average imposed heat flux, system pressure (saturated temperature) and vapor quality of R-134a on the measured data were explored in detail. The results indicate that at a higher vapor quality the condensation heat transfer coefficient and pressure drop are significantly higher. A rise in the refrigerant mass flux only causes a mild increase in the h r values for most cases. The corresponding rise in the Δ P f value is slightly larger. Furthermore, it is noted that the condensation heat transfer is only slightly better for a higher average imposed heat flux. But the associated rise in Δ P f is larger. Finally, at a higher system pressure the h r value is found to be slightly lower. But the effect of the system pressure on Δ P f is small. Correlations are also provided for the measured heat transfer coefficients and pressure drops in terms of the Nusselt number and friction factor.