| Title |
An Experimental Study on Film Condensation Heat Transfer Coefficients of R718 under Vacuum Pressure with Various Horizontal Tube Shapes |
| Authors |
Daegyu Lee ; Jin Man Kim ; Dong An Cha ; Seon-Chang Kim |
| DOI |
https://doi.org/10.6110/KJACR.2020.32.11.510 |
| Keywords |
열전달계수; 막응축; 진공압; 자연냉매; 물 Heat transfer coefficient; Film condensation; Vacuum pressure; Natural refrigerant; R718 |
| Abstract |
In this study, experiments were conducted to investigate film heat transfer coefficients of seven types of tube.
The saturated temperature of the refrigerant (R718) was fixed at 36.5℃. The flow rate of the cooling water inside the horizontal tube was 0.13~0.75 kg/s with controlling of the inlet temperature that ranged from 29 to 34℃. From experimental results, it was confirmed that the heat transfer coefficient improved when changing the surface shape of tube and the film condensation heat transfer coefficient was the largest at endcross 26 tube. And for the examined tubes, an empirical correlation between Nusselt number and film Reynolds number was suggested in exponential form. |