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- 3.16 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_forwardA cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.arrow_forwardA furnace wall comprises three layers of thickness 250 mm, 100 mm, and 150 mm with thermal conductivities of 1.65, k and 9. W/m K respectively. The inside is exposed to gases at 1250 ˚C with convection of 25 W/m2K, and the inside surface is at 1100 ˚C, the outside surface air at 25 ˚C with convection of 12 W/m2K. Determine the overall heat transfer coefficient in W/m2-K to 2 d.p. ?arrow_forward
- In a multilayered rectangular wall, the thermal resistance of the first layer is 0.005 °C/W, the resistance of the second layer is 0.2° C/W, and for the third layer it is 0.1 ° C/W. The overall temperature gradient in the multilayered wall from one side to another is 70° C. a. Determine the heat flux through the wall. b. If the thermal resistance of the second layer is doubled to 0.4° C/W, what will be its influence in % on the heat flux, assuming the temperature gradient remains the same?arrow_forwardIn a new residential project, you strongly believe that double-paned windows are ‘better’ than single-paned windows. Compare the rate of heat loss between single and double-paned windows(1.5 m x 1 m) if the thickness of each pane is (th = 0.4 cm) and (k = 0.9 W/m.K). The indoor and outdoor temperatures are 18 °C and 2 °C, respectively. Thickness of the air gap between the double-paned windows is (th = 1 cm), and (k = 0.022 W/m.K). Image credit: Windowwhirl.arrow_forwardIn a new residential project, you strongly believe that double-paned windows are ‘better’ than single-paned windows. Compare the rate of heat loss between single and double-paned windows (1.5 m x 1 m) if the thickness of each pane is (th = 0.4 cm) and (k = 0.9 W/m.K). The indoor and outdoor temperatures are 18 °C and 2 °C, respectively. Thickness of the air gap between the double-paned windows is (th = 1 cm), and (k = 0.022 W/m.K).arrow_forward
- In an experiment to measure the thermal conductivity of a plate of unknown material with area 1 m2 and thickness 0.1m, one of its surfaces is maintained at 100 °C and the other at 20 °C and a heat at the rate of 100 kW was supplied across it. Determine the thermal conductivity of the hot plate. Is the material metallic, non-metallic, or gas/liquid?arrow_forwardA 3-mm-diameter and 5-m-long electric wire is tightly wrapped with a 2-mm- thick plastic cover whose thermal conductivity is k=0.15 W/m · °C. Electrical measurements indicate that a current of 10 A passes through the wire and there is a voltage drop of 8 V along the wire. If the insulated wire is exposed to a medium at T=30°C with a heat transfer coefficient of h=12 W/m2 · °C, determine the temperature at the interface of the wire and the plastic cover in steady operation.arrow_forwardConsider a 2-m-wide 1.5-m-high wood-framed window with 3-mm-thick single-panel glass covering 85 percent of the area (k = 0.7 W/m °C). Pine wood (k = 0.12 W/m °C) is used for the frame, which is 5 cm thick. Inside, the heat transfer coefficient is 7 W/m2 °C, while outside, it is 13 W/m2 °C. The temperature in the room is kept at 24°C, while the outside temperature is 40°C. Considering and stating the necessary assumptions. calculate the percent inaccuracy in heat transfer when the window is supposed to be made entirely of glass. (b) Consider the continuous heat flow through a room's wall in the winter. As a result of the winds, the convection heat transfer coefficient at the outer surface of the wall is three times that of the inner surface. Which side of the wall do you believe the temperature will be closest to the temperature of the surrounding air? Explain.arrow_forward
- Question 2 A 2.2-mm-diameter and 10-m-long electric wire is tightly wrapped with a 1-mm-thick plastic cover whose thermal conductivity is k = 0.1 W/m·K. Electrical measurements indicate that a current of 13 A passes through the wire and there is a voltage drop of 8 V along the wire. If the insulated wire is exposed to a medium at T∞ = 19°C with a heat transfer coefficient of h = 20 W/m2·K, determine the temperature at the interface of the wire and the plastic cover in steady operation. Also determine if doubling the thickness of the plastic cover will increase or decrease this interface temperature.arrow_forwardAs seen in the attached figure, a 5-mm-diameter spherical ball (k = 15 W/m·K, Cp=480 J/kg·K) at 50°C is exposed to a medium at 15°C, with a combined convection and radiation heat transfer coefficient of 20 W/m2·K (to be used for option a and b) a) If the ball is covered by a 1-mm-thick plastic insulation (k = 0.13 W/m·K), determine whether the plastic insulation on the ball will help or hurt heat transfer from the ball. b) Assume that the ball is initially at uniform temperature of 50 °C. Determine how long it will take for the center of the ball to drop to 20 °C.arrow_forwardA long stainless-steel (AISI 316) steam pipe, with an inside diameter of 6.00 cm and an outside diameter of 8.00 cm, is covered with a layer of asbestos insulation (k = 0.150 W/m-K) 1.00 cm thick, which in turn is covered with foam insulation (k = 0.044 W/m-K) 6.00 cm thick. The inside surface temperature of the stainless-steel steam pipe is measured to be 250.0°C, while the outside surface of the foam is exposed to convection, T_inf = 25.0°C, h_inf = 15.0 W/m^2-K. • Draw and label a sketch of this system. Include dimensions, known temperatures, etc. • Draw and completely label the corresponding 1-D steady-state conduction resistor diagram. • Determine the heat transfer rate through the pipe per unit length. • Calculate the temperature at the asbestos/foam interface.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning