In a particular solar collector, dyed water runs down a vertical plate in a laminar film with thickness δo at the top.
The sun's rays pass through parallel glass plates (see Section 10.6) and deposit qs W/m2 in the film. Assume the water to be saturated at the inlet and the plate behind it to be insulated.
Develop an expression for δ(x) as the water evaporates. Develop an expression for the maximum length of wetted plate, and provide a criterion for the laminar solution to be valid.