A Flat-plate solar collector has two glass covers, a black absorber with ɛp = (0.95, mean plate temperature of 110°C at an ambient temperature of 10•C, Tei= 77.64°C, Tc2=36.41°C and a wind loss coefficient of 10 W/m².•C. Estimate its top loss cocfficicnt. If the back of the collcctor is insulated with 50mm of mincral wool insulation of k = 0.035 W/m.°C, what is its overall loss coefficient? (Neglect edge effects.). Plate-to-cover and cover-to-cover spacing is 25 mm. where, & =0.88. Cover1- cover2 Plate-coverl NU 2.96 2.43 K W/m-K (0.02787 (0.0305

PROBLEM 4: A black thermocouple is inside a chamber with black walls. If the air around the thermocouple is at 20°C, the walls are at 100-C, and the heat transfer coefficient between the thermocouple and the air is 75 W/m²K, what temperature will the thermocouple read?

An opaque surface which is insulated at the back side has a total, hemispherical absorptivity a=0.8 for solar radiation and a total, hemispherical emissivity of e=0.2. A solar radiation flux of 800 W/m2 is incident on this surface. The surface is exposed to the ambient air at T 300 K and convective heat transfer coefficient is h=15 W/m2 K. Neglect the sky radiation. • Sketch the heat fluxes received and dissipated by this surface • Estimate the equilibrium temperature of the surface (assume the surface temperature is higher than the ambient air temperature). 1.= 300 K, h-15 W/m*K 800 W/m? a-0.8 , e-0.2