Question

An industrial process involves the evaporation of water from a liquid film that forms on a well-insulated contoured surface. Dry air is passed over the surface, and from laboratory measurements the convection heat transfer correlation is of the form \overline{N u}_{L}=0.43 R e_{L}^{0.58} P r^{0.4} For an air temperature and velocity of 27°C and 2.5 m/s, respectively, what is the rate of evaporation from a surface of 1-m2 area and characteristic length L =1 m? Approximate the density of saturated vapor as pa sat = 0.0077 kg/m. What is the steady-state temperature of the liquid film?

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