| Title |
Flow Boiling Heat Transfer Characteristics of R22 Alternative Refrigerants in a Horizontal Smooth Tube |
| Keywords |
Heat transfer coefficients ; 열전달계수 ; Flow boiling ; 흐름비등 ; Wall temperature measurement method ; 벽면온도 측정방법 ; Wilson plot method ; 윌슨플롯방법 ; Alternative refrigerants ; 대체냉매 |
| Abstract |
Flow boiling heat transfer coefficients(HTCs) of R22, R134a, R407C, and R410A were measured for a horizontal plain tube. The test section was made of a copper tube of 8.8 mm inner diameter and 1000 mm length respectively. The refrigerant was heated by passing hot water through an annulus surrounding the test section. All tests were performed at a fixed refrigerant saturation temperature of 5℃ with mass fluxes of 100∼300 kg/m2s. HTCs were measured by two methods: the direct wall temperature measurement method and the indirect Wilson plot method. Experimental results showed that the Wilson plot method was affected greatly by the external test conditions and yielded inconsistent results. For the mass flux of 100 kg/m2s, HTCs were almost constant regardless of the quality for a given refrigerant, HTCs of R134a and R407C were similar to those of R22 while those of R410A were 60% higher than those of R22. For the mass fluxes of 200 and 300 kg/m2s, HTCs of R407C were almost the same as those of R22, while HTCs of R134a and R410A were 12∼13% and 20∼23% higher than those of R22 respectively. For pure refrigerant, Shah's correlation yielded a good agreement with the measured data both qualitatively and quantitatively. |