A solar pond, 1.5 m deep, is built in Pondicherry (11°56' N). The following values of global and diffuse radiation are measured by a on April 20 at 1.300 h horizontal pyranometer placed beside the pond (LAT): I=0.964 kW/m² Id=0.210 kW/m² Calculate the variation of the solar radiation flux as it penetrate through the pond.

1. Two large plates are maintained at a temperature of 900 K and 500 K respectively. Each plate has area of 6°. Compare the net heat exchange between the plates for the following cases. (i) Both plates are black (ii) Plates have an emissivity of 0.5 Given: T =900 K T, =500 K A=6m’ To find: (i) (Qu)u Plates have an emissivity of €= 0.5

A flat-plate collector with one glass cover is placed in horizontal. The absorber plate temperature is 95 oC and its emittance is 0,12. The glass cover temperature is 45 oC, and the (glass) cover has an emittance of 0.85. The plate-cover spacing is 15 mm. The ambient and surrounding temperature are equal at 25 oC. The wind velocity is 20 km/hour. If solar radiation is 850 W/m2 , and the plate absorptivity is 95%, calculate over all heat transfer coefficient losses and the useful energy (W/m2 ). ----- s

Determine the amount of acres of land necessary to generate 50 MW of solar power at noon in Philadelphia with an array of panels positioned horizontally. Assume that the panels are 21 % efficient and that the solar irradiation at noon is 900 W/m?

Concentrating collectors X and Y are constructed for heat generation. Both collectors have the same concentration factor of 14 and optical efficiency of 84.52%. The collector temperature is found to be 141.01 deg C for both collectors. For collector X, the incident solar irradiance is 775.37 W/m² and the heat transfer coefficient is 2.92 For collectorY, the heat transfer coefficient is 4.33 . Determine the incident solar irradiance on collector Y in W/m2, if it has the same efficiency as collector X. The ambient air temperature is 25 deg C.

2. (a)   Consider a 25-cm-diameter spherical ball at 700 K suspended in air and assume the emissivity of the ball to be ε=0.95.                     Calculate:       (i) the total emissive power in kW/m2;                                                (ii) the total amount of radiation emitted by the ball in 3 minutes.                     (b)   The inner and outer surfaces of a 25-cm-thick wall are at 27 oC and 45 oC, respectively. The outer surface of the wall exchanges heat by radiation with surrounding surfaces at 40 oC, and convection with ambient air at 42 oC with convection heat transfer coefficient of 9.0 W/m2 K. Solar radiation incident on the surface is at a rate of 150 W/m2. If the emissivity and the solar absorptivity of the outer surface are 0.75 and 0.85, respectively:                 (i) write the expression of the energy balance at the outer surface;…

The view factor integral in radiation heat transfer between two bodies A, and A, is given by IGE cos 0, cos 0, F = dA,dA, 1) TR2 A¡ Aj sin 0, sin 0, TR2 dA,dA, 2) Aj Aj F, = AA) rcose, sin 0, dA,dA, cos 0, cos 0, dA,dA, 4) AIAj TR2

Consider a 25-cm-diameter spherical ball at 700 K suspended in air and assume the emissivity of the ball to be ɛ=0.95. Calculate: (i) the total emissive power in kW/m_ (ii) the total amount of radiation emitted by the ball in 3 minutes.

Define Emissivity of some materials at 300 K.

A flat-plate solar collector, as shown in Fig. 1, is used to heat water by having water flow through tubes attached at the back of the thin solar absorber plate. The absorber plate has an emissivity and an absorptivity of 0.8. The top surface (* = 0) temperature of the absorber is To = 35 °C, and solar radiat ion is incident on the absorber at 600 W/m? with a surrounding temperature of 0 °C. The convection heat transfer coefficient at the absorber surface as 8 W/m?-K. Assuming constant thermal conductivity and no heat generation in the wall, i express the differential equation and the boundary conditions for steady one- dimensional heat conduct ion through the wall, obtain a relation for the variation of temperature in the wall by solving the differential equation, and ii iii. determine the net heat flux, ġo absorbed by the collector ε, α, Τ. Absorber plate Water tubes Insulation Fig. 1