The laminar boundary layer theory is used to analyze the film condensation on a vertical plate. The calculated result is well consistent with the experiment and empirical relation of the laminar film condensation. A c...The laminar boundary layer theory is used to analyze the film condensation on a vertical plate. The calculated result is well consistent with the experiment and empirical relation of the laminar film condensation. A convection number E is presented,which shows the contribution of convection to heat-transfer in film condensation. When E is less than 1,the condensation region is controlled by conduction. When E is far less than 1,the region is called Nusselt region. When E is larger than 1,the region of condensation is controlled by convection. When E is much more than 1,Co_m is proportional to Re_L^1/3.展开更多
An experimental study on R22 film condensation on single horizontal tubes(one smooth tube and two doubly enhanced ones) was conducted at the saturation temperatures of 32℃, 35℃ and 38℃ respectively. A modified Wi l...An experimental study on R22 film condensation on single horizontal tubes(one smooth tube and two doubly enhanced ones) was conducted at the saturation temperatures of 32℃, 35℃ and 38℃ respectively. A modified Wi lson plot was used to obtain the water-side and vapor-side heat transfer coeff icients. The results indicated that the experimental condensation heat transfer coefficients agreed with the Nusselt theory with ±10%. The water side heat tr ansfer coefficients of tube No.1 and tube No.2 were 2.78 and 2.99 times of t hat of smooth tube, respectively. At the same heat flux the condensation heat t ransfer coefficients of tube No.1 and tube No.2 were 8.2—18.0 times and 8. 1—12.4 times of the smooth tube, respectively. Thermal resistance analysis sh owed that the relative percentage of vapor-side thermal resistance increased wi th water velocity. When the thermal resistance values of the two sides were equ al, the water velocity of tube No.1 was 1.25 m·s-1(Re=2.41×104) and that of No.2 was 0.82 m·s-1(Re=1.54×104).For all cases, th e wall thermal resistance was less than 4 percentage. The reasons accounting fo r the superiority of tube No.1 were analyzed.展开更多
文摘The laminar boundary layer theory is used to analyze the film condensation on a vertical plate. The calculated result is well consistent with the experiment and empirical relation of the laminar film condensation. A convection number E is presented,which shows the contribution of convection to heat-transfer in film condensation. When E is less than 1,the condensation region is controlled by conduction. When E is far less than 1,the region is called Nusselt region. When E is larger than 1,the region of condensation is controlled by convection. When E is much more than 1,Co_m is proportional to Re_L^1/3.
文摘An experimental study on R22 film condensation on single horizontal tubes(one smooth tube and two doubly enhanced ones) was conducted at the saturation temperatures of 32℃, 35℃ and 38℃ respectively. A modified Wi lson plot was used to obtain the water-side and vapor-side heat transfer coeff icients. The results indicated that the experimental condensation heat transfer coefficients agreed with the Nusselt theory with ±10%. The water side heat tr ansfer coefficients of tube No.1 and tube No.2 were 2.78 and 2.99 times of t hat of smooth tube, respectively. At the same heat flux the condensation heat t ransfer coefficients of tube No.1 and tube No.2 were 8.2—18.0 times and 8. 1—12.4 times of the smooth tube, respectively. Thermal resistance analysis sh owed that the relative percentage of vapor-side thermal resistance increased wi th water velocity. When the thermal resistance values of the two sides were equ al, the water velocity of tube No.1 was 1.25 m·s-1(Re=2.41×104) and that of No.2 was 0.82 m·s-1(Re=1.54×104).For all cases, th e wall thermal resistance was less than 4 percentage. The reasons accounting fo r the superiority of tube No.1 were analyzed.
