| Title |
A Study of External Condensation Heat Transfer of Flammable Refrigerants |
| Keywords |
Flammable refrigerants ; 가연성 냉매 ; Horizontal plain tube ; 수평관 ; External condensation heat transfer coefficients ; HTCs, 외부 응축 열전달계수 ; Enhanced tubes ; 촉진관 ; Enhancement ratio ; 열전달 촉진비 |
| Abstract |
In this study, external condensation heat transfer coefficients(HTCs) of flammable refrigerants of propylene, propane, isobutane, butane, DME, and HFC32 were measured on a horizontal plain tube, 26fpi low fin tube, and Turbo-C tube. All data were taken at the temperature of 39℃ with a wall subcooling of 3～8℃. Test results showed a typical trend that condensation HTCs of flammable refrigerants decrease with increasing wall subcooling. HFC32 had the highest HTCs among the tested refrigerants showing 44% higher HTCs than those of HCFC22 while DME showed 28% higher HTCs than those of HCFC22. HTCs of propylene and butane were similar to those of HCFC22 while those of propane and isobutane were similar to those of HFC134a. Based upon the tested data, Nusselt's equation is modified to predict the plain tube data within a deviation of 3%. For 26fpi low fin tube, Beatty and Katz equation predicted the data within a deviation of 7.3% for all flammable refrigerants tested. The heat transfer enhancement factors for the 26fpi low fin and Turbo-C tubes were 4.6～5.7 and 4.7～6.9 respectively for the refrigerants tested indicating that the performance of Turbo-C tube is the best among the tubes tested. |