The specifications of a flat-plate collector is as follows: = 0.88, = 0.97, U =

The specifications of a flat-plate collector is as follows: τ = 0.88, α = 0.97, U = 1.3 Btu/h·ft2·oF. The heat removal factor for the collector is 0.92, the solar insolation is 210 Btu/h·ft2, and the ambient air temperature is 60oF. Determine
(a) The collector efficiency if the water enters the collector at 115oF
(b) The temperature of water at which the collector efficiency is zero. Take the incident angle modifier to be 1.