| Title |
Pool Boiling Heat Transfer Coefficients of New Refrigerants on Various Enhanced Tubes |
| Keywords |
Pool boiling heat transfer ; 풀비등 열전달 ; Low fin tube ; 낮은 핀관 ; Enhanced tube ; 촉진관 ; Enhancement ratio ; 촉진비 ; Alternative refrigerant ; 대체냉매 |
| Abstract |
Pool boiling heat transfer coefficients (HTCs) of HCFC123, HFC134a, HCFC22, HFC407C, HFC410A and HFC32 were measured on a horizontal smooth tube, 26 fpi low fin tube, Turbo-B and Thermoexcel-E enhanced tubes. An experimental apparatus was designed such that all tubes heated by cartridge heaters could be installed at the same time to save the refrigerant. Data were taken in the pool of 7℃ with the heat flux decreasing from 80 kW/m2 to 5 kW/m2. Test results showed that HTCs of pure refrigerants and those of a azeotrope were greatly influenced by reduced pressure. HTCs of HFC407C were 21∼25% lower than those of HCFC22 due to mass transfer resistance. For all refrigerants, enhanced tubes with sub-surface and sub-tunnels showed the largest heat transfer enhancement. Especially the largest heat transfer enhancement was obtained for HCFC123 whose reduced pressure is the lowest among all the refrigerants tested. This indicates that either Turbo-B or Thermoexcel-E enhanced tube would be the best choice when used with a low vapor pressure refrigerant. |