A 2 x 2 m flat plate solar collector for domestic hot water heating is shown in the figure. The incident solar radiation on the glass cover, which transmits 90% of the incident flux, is 750 W/m2. Water flows through the tubes soldered to the backside of the absorber plate, entering at a temperature of 25°C. The temperature of the glass cover is 27°C, and it radiates heat with an emissivity of 0.92 to the sky at –50°C. Additionally, the glass cover losses heat by convection to air at 20°C flowing over its surface at 30 km/h. Assume that the radiation heat transfer between the absorber plate and glass cover and the heat transfer through the back and sides of the collector is negligible.

A point source emits 200 radiant watts and has a luminous efficacy of 120 lumens/watt. Itsspatial distribution is spherically uniform. state any assumptions, check answer w bold text.  a) What is the luminous intensity of this source? 1910 cdb) What is the average illuminance on a unit sphere centered around the point source? 6000/pii lx or fcc) What is the illuminance at point p at the center of circular surface A? 212 Ixd) If surface A has a radius of 2 m, what is the illuminance at point q? 122 lxf) what is the total number of lumens incident onto surface a? ~2015lmg) The total reflectance of surface A is 0.50. What is the average exitance of surface A? 80 Im/m2

An electronic package with a surface area of 1 m² placed in an orbiting space station is exposed to space. The electronics in this package dissipate all 1 kW of its power to the space through its exposed surface. The exposed surface has an emissivity of 1.0 and an absorptivity 0.25. Determine the steady state exposed surface temperature of the electronic package (a) if the surface is exposed to a solar flux of 750 W/m², and (b) if the surface is not exposed to the sun.