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A concreate wall a surface area of 20 m2 and a thickness of 0.30 m separates conditioned room air from ambient air. The temperature of the inner surface of the wall (T1) is maintained at
(a) Determine the heat loss
(a total of 11 data points for each thermal conductivity value). Tabulate the result for all three cases in one table. Also provide a computer-generated graph [Heat loss,
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HEAT+MASS TRANSFER:FUND.+APPL.
- 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.arrow_forward1.37 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.arrow_forwardA pipe carrying superheated steam in a basement at 10C has a surface temperature of 150C. Heat loss from the pipe occurs by radiation (=0.6) and natural convection (hc=25W/m2K). Determine the percentage of the total heat loss by these two mechanisms.arrow_forward
- 1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.arrow_forwardThe 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?arrow_forwardA plane wall 15 cm thick has a thermal conductivity given by the relation k=2.0+0.0005T[W/mK] where T is in kelvin. If one surface of this wall is maintained at 150C and the other at 50C, determine the rate of heat transfer per square meter. Sketch the temperature distribution through the wall.arrow_forward
- A high-speed computer is located in a temperature-controlled room at 26C. When the machine is operating, its internal heat generation rate is estimated to be 800 W. The external surface temperature of the computer is to be maintained below 85C. The heat transfer coefficient for the surface of the computer is estimated to be 10W/m2K. What surface area would be necessary to assure safe operation of this machine? Comment on ways to reduce this area.arrow_forwardUsing Table 1.4 as a guide, prepare a similar table showing the orders of magnitude of the thermal resistances of a unit area for convection between a surface and various fluids.arrow_forward3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.arrow_forward
- HEAT TRANSFER (a) Determine the thermal conductivity of an insulating material given the following data: steel pipe with 0.1025 m inner diameter and 0.1150 m outer diameter, insulation thickness 3 cm, heat flow per meter is 150 W/m, steel thermal conductivity 55 W/m-°C, and overall temperature difference of 72.2°C. If the temperature of the steam inside the pipe is 128°C, (b) find the outside temperature of the insulating material.arrow_forwardA house has walls made out of steel with the following properties: Thickness 300 mm Density kg/m3 7800 Thermal Conductivity w/m-K 50 Specific Heat Capacity Embodied J/kg-K 500 MJ/kg 26 Energy Cost $/kg 0.70 The time that it will take, in hours, for the interior temperature to start changing after the exterior is exposed to a sudden temperature is:arrow_forwardConsider a wall that is 5 m high, 8 m long, and 0.22 m thick. The thermal conductivities of the various materials used, in W/m °C, are kA = kF = 2, kB = 8, kC = 20, kD = 15 and kE = 35. The left and right surfaces of the wall are maintained at uniform temperatures of 300 °C and 100 °C, respectively. If the heat transfer through the wall is one-dimensional, determine (a) the rate of heat transfer through the wall; b) the temperature at the point where sections B, D, and E meet, and c) the temperature drop across section F. Disregard any contact resistances between the interfaces.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning