| Title |
A Comparison of Flow Condensation HTCs of R22 Alternatives in the Multi-Channel Tube |
| Keywords |
Flow condensation ; 흐름 응축 ; Multi-channel flat tube ; 다채널 평판관 ; R22 ; 냉매22 ; R134a ; 냉매134a |
| Abstract |
Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4mm hydraulic diameter and 0.53m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1～0.9 at mass flux of 200～400kg/m2s and heat flux of 7.3～7.7kW/m2 at the saturation temperature of 40℃. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heating or cooling type heat transfer experimental apparatus. |