Solar radiation is incident on a 5-m2 solar absorber plate surface at a rate of 800 W/m2. Ninety-three percent of the solar radiation is absorbed by the absorber plate, while the remaining 7 percent is reflected away. The solar absorber plate has a surface temperature of
In addition, convective heat transfer occurs between the absorber plate surface and the ambient air of
Determine the efficiency of the solar absorber, which is defined as the ratio of the usable heat collected by the absorber to the incident solar radiation on the absorber.
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Chapter 1 Solutions
Heat and Mass Transfer: Fundamentals and Applications
- What are the important modes of heat transfer for a person sitting quietly in a room? What if the person is sitting near a roaring fireplace?arrow_forward2.34 Show that the temperature distribution in a sphere of radius . made of a homogeneous material in which energy is released at a uniform rate per unit volume , isarrow_forwardA hollow spherical iron container with outer diameter 20 cm and thickness 0.2 cm is filled with iced water at 0°C. If the outer surface temperature is 5°C, determine the approximate rate of heat loss from the sphere, in kW, and the rate at which ice melts in the container. The heat of fusion of water is 333.7 kJ/kg.arrow_forward
- Consider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is a) filled with still air with k = 0.0219 W/moC, b) free flowing air with h = 7.5 W/m2oC, c) evacuated, d) filled with urethane insulation with k = 0.026 W/moC, and e) filled with superinsulation that has an apparent thermal conductivity k = 0.00002 W/moCarrow_forwardA 3-m2 hot black surface at 80°C is losing heat to the surrounding air at 25°C by convection with a convection heat transfer coefficient of 12 W/m2 ·°C, and by radiation to the surrounding surfaces at 15°C. The total rate of heat loss from the surface is (a) 1987 W (b) 2239 W (c) 2348 W (d) 3451 W (e) 3811 Warrow_forwardConsider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is a) filled with still air with k = 0.0219 W/moC, b) free-flowing air with h = 7.5 W/m2oC, c) evacuated, d) filled with urethane insulation with k = 0.026 W/moC, and e) filled with superinsulation that has an apparent thermal conductivity k = 0.00002 W/moCarrow_forward
- Consider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is free flowing air with h = 7.5 W/m2oCarrow_forwardWhat are the mechanisms of heat transfer?arrow_forwardA 10-cm-high and 20-cm-wide circuit board houses on its surface 100 closely spaced chips, each generating heat at a rate of 0.08 W and transferring it by convection to the surrounding air at 25°C. Heat transfer from the back surface of the board is negligible. If the convection heat transfer coefficient on the surface of the board is 10 W/m2 ·°C and radiation heat transfer is negligible, the average surface temperature of the chips is (a) 26°C (b) 45°C (c) 15°C (d) 80°C (e) 65°Carrow_forward
- The roof of an electrically heated home is 12m long, 16m wide, and 0.50m thick, and is made of a flat layer concrete whose thermal conductivity is k=0.8W/m 2 ·°C. The temperature of the inner and outer surfaces of the roof one night are measured to be 12°C and 1°C, respectively, for a period of 12 hours. Determine a) the rate of heat loss through the roof that night b) the cost of that heat loss to the home owner if the cost of electricity is $0.14/kWh.arrow_forwardA hot water pipe at 80°C is losing heat to the surrounding air at 5°C by natural convection with a convection heat transfer coefficient of 25 W/ m2.°C. The rate of heat loss from the pipe by convection is to be determined.arrow_forwardThe inner and outer surfaces of a 0.5-cm-thick 2-m × 2-m window glass in winter are 15°C and 6°C, respectively. If the thermal conductivity of the glass is 0.78 W/m·°C, determine the amount of heat loss, in kJ, that occurs through the glass over a period of 10 h. What would your answer be if the glass were 1 cm thick?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning