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The heat flux that is applied to one face of a plane wall is
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Chapter 1 Solutions
Introduction to Heat Transfer
- A 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_forward1.10 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_forwardA 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_forward
- A plane wall, 7.5 cm thick, generates heat internally at the rate of 105 W/m3. One side of the wall is insulated, and the other side is exposed to an environment at 90C. The convection heat transfer coefficient between the wall and the environment is 500 W/m2 K. If the thermal conductivity of the wall is 12 W/m K, calculate the maximum temperature in the wall.arrow_forwardShow that the rate of heat conduction per unit length through a long, hollow cylinder of inner radius ri and outer radius ro, made of a material whose thermal conductivity varies linearly with temperature, is given by qkL=TiTo(rori)/kmA where Ti = temperature at the inner surface To = temperature at the outer surface A=2(rori)/ln(ro/ri)km=ko[1+k(Ti+To)/2]L=lenthofcyclinderarrow_forward2.38 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.arrow_forward
- 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.arrow_forwardThermodynamics In a solid sphere of 0.2 m diameter, heat is generated at the rate of 1.2 x 106 W/m3. The center temperature is 300°C. Conductivity is 50 W/m-K. What is the surface temperature?arrow_forwardI need answer within 20 minutes please please with my best wishesarrow_forward
- Plaster Insulation Brick Inside Outside Air Air R/2 R3/2 G R/2 A particular house wall consists of three layers and has a surface area A. The inside layer is made of plaster board, the middle layer is made of fiberglass insulation, and the outside layer is made of brick. The thermal conductivity of all three layers is known, and the thickness of the plaster board and siding are also known. The convection coefficient for the inside and outside wall surfaces are known: System_Parameters - (h; = 40.0 h, = 60.0 k = 0.2 k = 0.04 k3 = 0.3 A= 30.0) System_Parameters = (L = 10.0 L2= unknown L3 = 100.0 cp1 = 950.0 c p2 = 10.0 cp3= 800.0 P1 = 700.0 Pz = 0.5 P3= 2000.0) W - mm; A ~ m²; k ~. m °C ;p~ 8: T ~ °C kg °C L m² °C m- a) If the thermal capacitances of the walls is ignored, How thick must the insulation layer be so that the heat loss is no greater than 400W if the outside temperature is -15-C? b) Now consider the situation where the thermal capacitance is also considered. Develop the state…arrow_forwardA room is 3600 mm in height. It has wall length and width of 5 meters and 6 meters, respectively. Considering the internal temperature be 18 C and outside temperature be 30 C. Wall U = 29 W/m^2-C, floor U=15 W/m^2-C, and ceiling U = 23 W/m^2-C. The ground temperature is about 25 C. Identify the heat load through transmission in BTU/hr. please answerarrow_forwardQ1: Consider a large plane wall of thickness L = 0.4 m, thermal conductivity k=2.3 W/m °C, and surface area A= 20 m2. The left side of the wall at x= 0 is subjected of T1 = 80°C. while the right side losses heated by convection to the surrounding air at T-15 °C with a heat transfer coefficient of h=24 W/m2 C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, and (c) evaluate the rate of heat transfer through the wall Ans : (c) 6030 Warrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
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