A solar flux of 700 W/m2 is incident on a flat-plate solar collector used to heat water The area of the collector is 3 m2 and 90% of the solar radiation passes through the cover glass and it absorbed by the absorber plate. The remaining 10% is reflected away from the collector Water flows through the tube passages on the back side of the absorber plate and is heated from an inlet temperature T, to an outlet temperature T o The cover glass, operating at a temperature of 30 degree C. has an emissivity of 0.94 and experiences radiation exchange with the sky at - 10 degree C. The convection coefficient between the cover glass and the ambient air at 25 degree C is 10 W/m2 K a. Perform an overall energy balance on the collector to obtain an expression for the rate at which useful heat is collected per unit area of the collector. qw Determine the value of qc
b. Calculate the temperature rive of the water. if the flow rate is 0.01 kg/s. Assume the specific heat of the water to be 4179 J/kg K.
c. The collector efficiency eta is defined as the ratio of the useful heat collected to the rate at which solar energy is incident on the collector What is the value of eta?