Saturated steam at 34 kPa condenses on a 1-m-tall vertical plate whose surface temperature is uniform at 60°C. Compare the average heat transfer coefficient and the value of the coefficient 1/3, 2/3, and 1 m from the top. Also, find the maximum plate height for which the condensate film will remain laminar.
GIVEN
? Saturated steam condensing on a vertical plate
? Steam pressure (p) = 34 kPa
? Plate height (L) = 1 m
? Plate surface temperature (Ts) = 60°C (uniform)
FIND
(a) The average heat transfer coefficient (hc)
(b) The local heat transfer coefficient (h?) at x = 1/3 L, 2/3 L, and L
(c) The maximum height for which the condensate film will remain laminar
ASSUMPTIONS
? Steady state
? Film condensation occurs
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 13, for saturated water at 34 kPa
(a) The average heat transfer coefficient is given by Equation (9.21)
(b) The local heat transfer coefficient is given by Equation (9.18)
(c) Turbulence occurs when
Combining the definition of the Reynolds number with Equation (9.14)
Solving this for the critical film thickness
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