2- For general office room, only one side of it is exposed to the outside while the other sides are faced to conditioned spaces. If we neglect the heat loss through the roof and floor calculate the heat loss through the exposed wall if it consists of (19 mm plaster outside cement & sand), (20 cm hollow concrete block, sand &gravel 3 hollows) and (12.5 mm plaster inside, gypsum and sand), if the exposed wall has a window represent 50 percent of it. If the inside and outside temperatures are 22 °C and 0°C calculate the heat loss through the exposed wall. (Assume the thermal conductivity for materials)

On a winters day the outside temperature of a 15 inch thick concrete wall is -25F, the wall is 16 ft long and 10 ft high. How manu BTU are required to keep the inside of the wall at 75F? Assume walls thermal conductivity is 0.8BTU/h ft F. Show detailed solutions

Q2/ A composite wall is formed of a 2.5 cm copper plate, a 3.2 mm layer of asbestos, and a 5 cm layer of fiberglass. The wall is subjected to an overall temperature difference of 560 C. Calculate the heat flow per unit area through the composite structure.

[2] A reservoir of hot water kept at 380K is well insulated except for a copper rod with a cross sectional area of 0.25 m? and a length of 0.50 meters. The rod is also well insulated except for its ends and the other end is in a second well insulated reservoir of water held at 280K. a) Determine the rate of heat flow through the copper rod. b) Calculate the temperature at the center of the rod (0.25 meters from either end). Then extend the process to find the temperature at each point 0.1m along the rod. c) Calculate the rate of entropy change at each end of the rod. d) Using your answer for (c), show that the statements "Heat flows spontaneously from high temperature to low temperature." and "Any spontaneous process causes the entropy of the universe to increase." are logically equivalent for situations with heat flow. e) Each reservoir of water holds 1 m of water. With a steady flow established, the power fails so that the heating and cooling of the water ceases. What are the…

you are assigned by your food engineering professor to assist a food manufacturing company as part of your task. On your first day of report, the owner wants to know if their furnace is still in condition, in which the heat loss per square meter should be at least 1,000 W/m2. The details of the furnace are as follows. The furnace wall is 1m by 1m. It is made up of 3 layers, in which the inner wall is made up of fire brick, followed an insulating brick and finally, red brick for the outer layer. You checked the inside surface temperature and got a temperature of 870oC which is 830oC hotter than the outer surface. Other data are provided from the furnace manual and specs. Co-efficient of thermal conduciveness and thickness of the layers are as follows: 1.0 W/m-K, thickness: 22 cm 0.12 W/m-K, thickness: 7.5 cm 0.75 W/m-K, thickness: 11 cm

3.6 Heat losses through windows in buildings are substantial. What would be the percentage reduction in heat loss that would be mitigated by replacing a window containing a single pane of glass with (a) double-pane low-E insulating glass or (b) a 3-inch-thick sheet of expanded polystyrene sheet? The quoted R values for these items are: • single pane of glass: 0.90 ft 2 hr ° F/Btu, • double pane of low-E insulating glass: 2.3 ft 2 hr ° F/Btu, • 1-inch-thick sheet of polystyrene sheet: 4.0 ft 2 hr ° F/Btu.

To 8. Ti 1. 2. 3. 4" Common Brick 1/2" OSB Sheathing 3-1/2" x 1-1/2" (2x4) Yellow Pine Studding placed on 16" center 4. 5. 3-1/2" Figerglass Insulation 1/2" Drywall A wall of a house as shown in the accompanying sketch is 10 ft. high and 30 ft. long and has no windows. The outside heat transfer coefficient, h., is 6.0 Btu/hr ft2°F and the inside convective heat transfer coefficient hi is 1.45 Btu/hr ft2°F. 6. Calculate the heat loss through the wall if the house is heated such that the room air temperature, Ti, is 70°F on a day when the outside air temperature, T., is 0°F. State all assumptions and list the thermal resistances and thermal conductivities for 3 each selection of the wall. 7. For this problem, what would be the value of the overall heat transfer coefficient, U? Ans: U = 0.056 Btu/hr ft2ºF You are asked to design a metal hot dog holder for roasting hot dogs over an open campfire. The holder is to be designed such that while the end holding the hot dog becomes cherry red…

The thermal resistance for convection at the outer surface of the hollow cylinder is a. None of the options b. Re 1/hrL c. Rc 1/2nhrL %3D d. R= 2 nhrL %3D

What is the thermal resistance of a 3 in fired clay brick with density of 120 Ibm/ft3 a. 0.422 b. 6.8 c. 0.48 d. 6.2

An office space contains one (6`x 3`) well- fitted door made of nominal 2" wood. The heat loss through door is (517.2 Btuh) if Tb.l.=80 F and To= -10 F. ? True or false