Using some simplifying assumptions the average heat

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Unformatted text preview: ator by ND. For low vapor velocities, film condensation heat transfer inside horizontal tubes can be determined from hinternal Ts) and represents heat transfer during condensation per unit mass of condensate. Here Cpl is the specific heat of the liquid in J/kg · °C. Using some simplifying assumptions, the average heat transfer coefficient for film condensation on a vertical plate of height L is determined to be hvert Equations for vertical plates can also be used for laminar film condensation on the upper surfaces of the plates that are inclined by an angle from the vertical, by replacing g in that equation by g cos . Vertical plate equations can also be used to calculate the average heat transfer coefficient for laminar film condensation on the outer surfaces of vertical tubes provided that the tube diameter is large relative to the thickness of the liquid film. The average heat transfer coefficient for film condensation on the outer surfaces of a horizontal tube is determined to be 0.555 g l( l l (Tsat ) k3 l h Ts) fg 3 C (T 8 pl sat 1/4 Ts) and Revapor D inlet 35,000 where the Reynolds number of the vapor is to be evaluated at the tube inlet conditions using the internal tube diameter as the characteristic length. Finally, the heat transfer coefficient for dropwise condensation of steam on copper surfaces is given by hdropwise 51,104 2044Tsat , 255,310 22°C Tsat Tsat 100°C 100°C where Tsat is in °C and the heat transfer coefficient hdropwise is in W/m2 · °C. cen58933_ch10.qxd 9/4/2002 12:38 PM Page 553 553 CHAPTER 10 REFERENCES AND SUGGESTED READING 1. N. Arai, T. Fukushima, A. Arai, T. Nakajima, K. Fujie, and Y. Nakayama. “Heat Transfer Tubes Enhancing Boiling and Condensation in Heat Exchangers of a Refrigeration Machine.” ASHRAE Journal 83 (1977), p. 58. 2. P. J. Berensen. “Film Boiling Heat Transfer for a Horizontal Surface.” Journal of Heat Transfer 83 (1961), pp. 351–358. 3. P. J. Berensen. “Experiments in Pool Boiling Heat Transfer.” I...
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This note was uploaded on 01/28/2010 for the course HEAT ENG taught by Professor Ghaz during the Spring '10 term at University of Guelph.

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