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Effect of lubricating oil contamination on evaporation in refrigerants R12 and R22
Author(s) -
Cawte Howard,
Sanders David A.,
Poland G. Anthony
Publication year - 1996
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/(sici)1099-114x(199608)20:8<663::aid-er181>3.0.co;2-m
Subject(s) - refrigerant , evaporator , evaporation , heat transfer coefficient , thermodynamics , chemistry , copper , heat transfer , heat flux , analytical chemistry (journal) , materials science , metallurgy , heat exchanger , chromatography , physics
An investigation has been made into the effect of oil concentration on evaporation heat transfer coefficients in refrigerant‐oil mixtures flowing in a horizontal tube. A new correlation is presented for heat transfer coefficients in convective evaporation of refrigerant‐oil mixtures that predicts the results of the present study within approximately ±20%. The paper reports measurements of evaporation heat transfer coefficients in refrigerants R12 and R22, both oil‐free and with two concentrations of Shell Clavus 32 oil. A 1·8 m long ⅜ in O/D copper tube (8·05 mm I/D) was used, at evaporation temperatures of −5°C, 0°C and +5°C. Heat flux and mixture mass velocity were kept constant at 2500 W m −2 and 155 kg m −2 s −1 , respectively, and measured coefficients were in the range of 1400 to 3900 W m −2 K −1 . The results showed that, for a complete evaporator, 2% oil may be expected to increase the heat transfer coefficient by 12%, but 10% oil returns the coefficient to oil‐free values.