Question

6.83 A disk of 20-mm diameter is covered with a water film. Under steady-state conditions, a heater power of 200 mW is required to maintain the disk-water ilm at 305 K in dry air at 295 K and the observed evaporation rate is 2.55 × 10-4 kg/h. Air T 295 K Water film, T 305 K Disk, D = 20 mm Heater, 200 m (a) Calculate the average mass transfer convection (b) Calculate the average heat transfer convection (c) Do the values of h and h satisfy the heat-mass (d) If the relative humidity of the ambient air at coefficient m for the evaporation process. coefficient h. analogy? 295 K were increased from 0 (dry) to 0.50, but the power supplied to the heater was maintained at 200 mW, would the evaporation rate increase or decrease? Would the disk temperature increase or decrease?

Answer 1

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