Heat transfer of R-134a in single-tube spray evaporation including lubricant effects and enhanced surface results

Single-tube spray evaporation experimental tests were conducted in order to evaluate the average wall heat transfer coefficients for seven different commercially available tubes. Liquid film supply rates were held constant in order to evaluate the effects of the enhancement on shell-side heat transfer under similar conditions. Because the spray evaporation phenomenon is so different from pool boiling, both condensation-type and evaporation-type enhanced surfaces were evaluated. A comparison of the results for all of the tubes showed that the enhanced condensation surfaces performed better than the enhanced boiling surfaces. In addition, the 26-fpi surface tested marginally better than the 40-fpi surface.

Heat transfer of R-134a in single-tube spray evaporation including lubricant effects and enhanced surface results Conference Paper