Condensing and evaporating heat transfer and pressure drop characteristics of an ozone friendly refrigerant HFC-134a and a HCFC refrigerant R-22, flowing inside a 9.5 mm (3/8 in) OD axially grooved tube were investigated experimentally to obtain the quasi-local heat transfer data and the correlations. When compared to R-22 at the same refrigerant flow rate, the condensing heat transfer coefficients for R-134a are 8 percent to 18 percent higher, and the pressure drop is 50 percent higher. The evaporating heat transfer coefficient with R-134a is about the same for mass velocity below 270 kg/m2-s and decreases above that velocity, relative to R-22. Performance characteristics are compared with data from literature reports.

Issue Section:
Phase Change and Multiphase Heat Transfer
Keywords:
Condensation, Evaporation, Refrigeration
Topics:
Evaporation, Heat transfer, Pressure drop
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