insulated. What is the minimum thickness of styrofoam insulation (k = 0.030 W/m K) that must be applied to the top and side walls to ensure a heat load of less than 500 W, when the inner and outer surfaces are -10 and 35°C? 1.10 A freezer compartment consists of a cubical cavity that is 2 m on a side. Assume the bottom to be perfectly

insulated. What is the minimum thickness of styrofoam insulation (k = 0.030 W/m K) that must be applied to the top and side walls to ensure a heat load of less than 500 W, when the inner and outer surfaces are -10 and 35°C? 1.10 A freezer compartment consists of a cubical cavity that is 2 m on a side. Assume the bottom to be perfectly

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.26P

See similar textbooks

Similar questions

2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)
Required info: There is a 2.00 cm thick stagnant air pocket. a) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m-K and of cork is 0.0460 W/m-K. b) What thickness of tin would be required for the same R-factor as a 2.00-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m:K and of tin is 66.8 W/m-K. THANK U
3. A composite plain wall is to be constructed of (1/4)-in. stainless steel (k-17.03 W/m-K), 3-in. of corkboard (k=0.04 W/m-K) and (1/2)-in. of plastic (k=2.6 W/m-K). (a) Draw a thermal circuit for the steady-state heat conduction through this wall; (b) Evaluate the individual thermal resistances of each material layer; (c) Determine the heat flux if the inside steel surface is maintained at 400 K and the outer surface of plastic surface is held at 300 K; and (d) What are the temperatures on each surface of the corkboard under these conditions?
Q2/ A metal plate of 4mm thickness (k = 95.5 W/m°C) is exposed to vapor at 100°C on one side and cooling water at 25°C on the opposite side. The heat transfer coefficients on vapor side and waterside are 14500 W/m^2°C and 2250 W/m^2 °C respectively. Determine the overall heat transfer coefficient *
Problem 5.18: A furnace has inside dimensions of 1 m × 1.2 m × 1.5 m. The walls are 0.25 m thick. The inside surface is at 750°C while the outside surface is at 80°C. If the conductivity of the material is 0.45 W/mK determine the heat loss, taking into account the corner and edge effects and also the bottom. (shape factors are taken from hand books). h-1
A boiler furnace wall must have a heat loss no greater than 700 Btu/hr~ft2 and is madeof a material with a thermal conductivity of 0.60 Btu/hr~ft~F. The inner wall surfacetemperature is '2000°F, and the outer surface temperature is 800°F. What wall thick~ness is required?
Answer within 10 minutes : The temperature at the inside surface of an oven is 460 oF. The inside wall of the oven is made of brick and is 8 inch thick. The thermal conductivity of the brick is 2.2 Btu/hr.ft2.(oF/ft). The outside of the oven is covered with a 3-inch layer of asbestos as insulation, which has a thermal conductivity of 0.11 Btu/hr.ft2.(oF/ft). If the outer surface of the insulation has a temperature of 100 oF , calculate the amount of heat lost through 2 ft2 of wall area in 3 hours.
27c) A plane wall is having 160 mm thickness, ‘b’ mm width and its height is three times the width is having a thermal conductivity of 14 W/mK. The surface temperatures are at 2000oK and 400o K. The heat flow across the plane wall is 465 W Calculate the width, height and area of the wall?
1. A 140 mm thick wall of 5 m x 3 m size is made of red brick (k = 0.6 W/m-K). It is covered on both sides by layers of plaster, 2 cm thick (k = 0.71 W/m-K). The wall has a double pane window size of 120 cm x 120 cm. The double pane window consists of 2 sheets of glass 6 mm thick (k = 0.96 W/m-K) separated by 138.8 mm thick air gap (k = 0.025 W/m- K). If the inner and outer surface temperatures are 18°C and 37°C, determine the total rate of heat transfer (W) through the composite wall and glass window. Express your final answer in five significant figures.
Question 1 The exterior wall of a building consists of 100 mm thick face brick (k = 0.9 W/m-K), 40 mm thick polystyrene insulating board (k = 0.036 W/m-K), 125 mm thick concrete block (k = 1.8 W/m-K) and 15 %3D mm thick interior gypsum board (k = 0.18 W/m-K). The inside and outside convective heat transfer coefficients are 6.5 W/m2-K and 22.5 W/m2-K, respectively. The outside air temperature is -5°C and the inside air temperature is 20°C. The wall is 3 m high and 15 m long. Calculate the rate of heat loss (in W) through the wall. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 1, calculate the temperature (in °C) of the interior surface of the wall. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 1, calculate the temperature (in °C) of the exterior surface of the wall. Round your answer to 2 decimal places. Add your answer
c) A steel pipe of 100 mm bore, and 10 mm bore thickness, carrying dry saturated steam at 28 bars, is insulated with a 40 mm layer of moulded insulation. This insulation in turn is insulated with a 60 mm layer of felt. The atmospheric temperature is 15 °C. Calculate: (i) the rate of heat loss by the steam per metre pipe length. (ii) the temperature of the outside Dimensions in mm surface.zzzzzzz h₂-15 W/m²K Steel k₁=50 W/mK AVALEHT Ø100 1₂ " Steam 28 bar h-550 W/m²K, Inner heat transfer coefficient = 550 W/m² K Outer heat transfer coefficient = 15 W/m² K Thermal conductivity of steel = 50 W/m K Thermal conductivity of felt = 0.07 W/m K Moulded insulation Felt Moulded insulation K₂=0.09 W/mK Thermal conductivity of moulded insulation = 0.09 W/m 40 10. A 60 15°C Felt K₁=0.07 W/mK zzzzzzzz
What is the rate of heat transfer, temperature gradient, and the direction of the heat transfer through a piece of Celotex 3 ft by 8 ft by 1 in. in thickness, if the temp of one surface is 80°F and of the other side is 60°F? - thermal conductivity of Celotex in AES = 0.028.