2. A refrigerated cold room wall has a thickness of 100mm and a thermal conductivity 0.14 W/m-K. The room wall has a 60mm thick internal lining of cork having a thermal conductivity of 0.05 W/m.K. The thermal conductance between the exposed faces and the respective atmosphere is 12 W/m²-K. If the room is maintained at 0°C and the external atmospheric temperature is 20°C, Calculate the heat loss rate through 1m² of the wall.

2. A refrigerated cold room wall has a thickness of 100mm and a thermal conductivity 0.14 W/m-K. The room wall has a 60mm thick internal lining of cork having a thermal conductivity of 0.05 W/m.K. The thermal conductance between the exposed faces and the respective atmosphere is 12 W/m²-K. If the room is maintained at 0°C and the external atmospheric temperature is 20°C, Calculate the heat loss rate through 1m² of the wall.

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.

Chapter4: Numerical Analysis Of Heat Conduction

Section: Chapter Questions

Problem 4.12P

See similar textbooks

Similar questions

1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss through a wall of 10-cm thickness is . If a thermocouple at the inner surface of the wall indicates a temperature of 22°C while another at the outer surface shows 6°C, calculate the thermal conductivity of the concrete and compare your result with the value in Appendix 2, Table 11.
As a designer working for a major electric appliance manufacturer, you are required to estimate the amount of fiberglass insulation packing (k = 0.035 W/m K) that is needed for a kitchen oven shown in the figure below. The fiberglass layer is to be sandwiched between a 2-mm-thick aluminum cladding plate on the outside and a 5-mm-thick stainless steel plate on the inside that forms the core of the oven. The insulation thickness is such that the outside cladding temperature does not exceed 40C when the temperature at the inside surface of the oven is 300C. Also, the air temperature in the kitchen varies from 15Cto33C, and the average heat transfer coefficient between the outer surface of the oven and air is estimated to be 12.0W/m2K. Determine the thickness of the fiberglass insulation that is required for these conditions. What would be the outer surface temperature when the inside surface of the oven is at 475C?
1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.
2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
The heat transfer coefficient between a surface and a liquid is 57 W/(m2K). How many watts per square meter will be transferred in this system if the temperature difference is 10C?
A large concrete wall is 300 mm thick and has a thermal conductivity of 1.2 W/m C. The heat flux through the wall is 100 W/m2. The higher-temperature surface of the wall is at 42 C. What is the temperature of the other surface of the wall?
A cold-storage room is constructed of an inner layer of 14 mm of pine with thermal conductivity of 0.15 W/m K, and an outer layer of 75 mm of concrete with thermal conductivity of 0.75 W/m K. The wall surface temperature is 258 K inside the cold room and 298 K at the outside surface of the concrete. Calculate the heat loss in W per 1 m2. Please keep one decimal and take positive value for the final answer.
A cold-storage room is constructed of an inner layer of 11 mm of pine with thermal conductivity of 0.15 W/m K, and an outer layer of 75 mm of concrete with thermal conductivity of 0.75 W/m K. The wall surface temperature is 253 K inside the cold room and 299 K at the outside surface of the concrete. Calculate the heat loss in W per 1 m2. Please keep one decimal and take positive value for the final answer.
If the rate of heat flow through a furnace wall is 0.94 kW/m². The wall consisting of 0.20 m thick inner layer of chrome brick, a center layer of kaolin brick of 10.0 cm and an outer layer of masonry brick 100 mm thick, having a thermal conductivity of 1.25 W/m°C , 0.74x10ª kW/m°C_and 0.555x10³ kW/m°C respectively. The unit surface conductance at the inner surface is 74 W/m2 °C and the outer surface temperature is 70 °C . The temperature of the gases inside the furnace is 1670 °C , assume steady heat flow, Calculate the following: 1- The temperatures of the gases inside the furnace. 2- The interior surface temperature of the inner and outer layers.
The temperature at the inner and outer surfaces of a boiler wall made of 25 mm thick steel and covered with an insulating material of10 mm thickness are 300 C and 50C respectively. If the thermal conductivities of steel and insulating material are 58W/mC and 0.116W/mC respectively, determine the total resistance through the boiler wall. (Note area of sample boiler wall is 8 m2)
A furnace wall is constructed of a firebrick that is 6 inches thick. The temperature of the inside of the wall is 1300°F, and the temperature of the outside of the wall is 175°F. If the mean thermal conductivity under these conditions is 0.17 BTU/hr-ft-°F. What is the rate of heat loss through 10 square feet of wall surface?
a flat wall is covered with a layer of insulation 1.0 in. thick whose thermal conductivity is 0.8 Btu/hr-ft- F. the temperature of the wall on the inside of the insulation is 600F. the wall loses heat to the environment by convection on the surface of the insulation. the average value of the convection heat transfer coefficient on the inslation surface is 950 Btu/hr-ft^2-F. compute the bulk temperature of the environment if the outer surface of the insulation does not exceed 105 F.