Steam condensation on copper-enhanced tubes used in an absorption refrigeration system

For the condenser of an absorption refrigerator, many enhanced geometries (smooth, corrugated, notched, floral, etc.) have been developed and are used in the field. However, no quantitative condensation heat transfer data is available in the literature. In the present study, seven enhanced tubes (floral, notched, endcross, corrugated, endcross floral, notched floral, endcross corrugated) used for condensers of absorption refrigerators were tested at the saturation temperature 40^◦C. Results showed that significant enhancements of condensation heat transfer were noted, especially for compound enhanced tubes. At the wall subcooling 2^◦C, the enhancement was 133% for the endcross corrugated tube, 77% for the endcross floral tube, and 73% for the notched floral tube. Between the notched and endcross tubes, larger enhancement was obtained from the notched tube (62% vs. 43%). The corrugated tube also yielded a significant amount (51%) of enhancement. In general, compound enhanced tubes showed higher heat transfer coefficients than single enhanced tubes. Of single enhancement geometries, three-dimensional shapes (notch, endcross) yielded higher enhancements than the floral shape and yielded approximately equal enhancements to the corrugated shape.