| Summary: | 碩士 === 國立交通大學 === 機械工程研究所 === 85 === An experimental refrigerant loop has been established in the present study to measure the condensation heat transfer coefficient h and pressure drop ΔP of R-134a in a vertical plate exchanger. Two vertical counter flow channels were formed int he exchanger by three plates of comercialized geometry with a corrugated sin 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, imposed heat flux, system pressure (saturated temperature) and vapor quality of R-134a on the measured data were explored.
The results indicate that at a higher vapor quality the condensation heat transfer and pressure drop are significantly higher. The increase in the pressure drop with the quality is much larger. While a rise in the refrigerant mass flux only causes a mild increase in the h values for most cases. The corresponding rise in the Δp is slightly larger. Furthermore, it was noted that the condensation heat transfer is only slightly better for a higher imposed heat flux. But the associated ΔP is larger. However, at a higher system pressure the rise in h with the heat flux can be significant. finally, at a higher system pressure the h value was fond to be slightly lower. But the effects of the system pressure on ΔP is small. Correlations were also developed for the measured heat transfer coefficients and pressure drops in terms of the Nusselt number and friction coefficient.
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