Experimental heat transfer coefficients for R12, R134a, and mixture of R22/R124/R152a (52%/33%/15%) are reported. Tests were conducted using a single-tube evaporator test facility. The test section used was a 2.43 m (8ft) long, 7.04 mm (0.277 in.) inside diameter, horizontal, smooth copper tube. Heat was applied to the test section using electric resistance heaters. Test parameters were varied as follows – mass flux, 25 to 100 kg/m2×s (19 to 76 klbm/ft2×h), heat flux, 2 to 10 kW/m2 (600 to 3,200 Btu/h×ft2), quality, 10% to 90%, and saturation temperature, -15 deg C to 5 deg C (5 deg F to 41 deg F). The heat transfer coefficients for R134a were higher than those for R12 using equivalent mass flux and cooling capacity bases. The heat transfer coefficients for the mixture were lower than those for R12 using equivalent mass flux and cooling capacity bases. The correlations of Shah and Kandlikar were compared with the experimental heat transfer coefficients. For correlating purposes, some high mass flux data with annular flow patterns, reported previously, are also included. An empirical correlation developed for annular flow data using an asymptotic form was modified to account for the decrease in heat transfer due to the wavy-stratified flow pattern in the low mass flux cases.
KEYWORDS: properties, evaporators, heat transfer coefficient, R12, R134a, R22, R124, R152a, refrigerants, mixtures, heat flow, experiment, testing, saturation temperature, comparing, refrigeration.
Citation: Symposium, ASHRAE Trans. 1994, Vol.100, Part 1,
Product Details
- Published:
- 1994
- File Size:
- 1 file , 1.3 MB
- Product Code(s):
- D-17762
