A recent theoretical model for condensation on low-finned tubes has been used to examine and compare the performance characteristics of CFC refrigerants and possible medium and long-term replacements. The fluids investigated are CFC11, CFC12, HCFC123, HFC134a and ammonia. The dependence of "enhancement ratio" on fin spacing, thickness and height has been calculated. All three dimensions have a significant effect on enhancement. The sensitivity of the enhancement ratio to the geometric parameters (in the vicinity of the optimum values) is less for ammonia than for the other fluids studied. A significant finding is that, for fluids other than ammonia, thinner fins than those currently used give appreciably improved performance. Highest values of enhancement ratios (with optimum fin dimensions) are around 24 for CFC12 and HFC134a, around 17 for HCFC123, around 14 for CFC11 and around 5 for ammonia.
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