A transparent film is to be bonded onto the top surface of a solid plate inside a heated chamber. For the bond to cure properly, a temperature of 70°C is to be maintained at the bond, between the film and the solid plate. The transparent film has a thickness of 1 mm and thermal conductivity of 0.05 V’mK, while the solid plate is 13 mm thick and has a thermal conductivity of 1.2 W/m⋅K. Inside the heated chamber, the convection heat transfer coefficient is 70 W/m2 K. If the bottom surface of the solid plate is maintained at 52°C, determine the temperature inside the heated chamber and the surface temperature of the transparent film. Assume thermal contact resistance is negligible.
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Chapter 3 Solutions
Heat and Mass Transfer: Fundamentals and Applications
- Under steady-state conditions, the wall of a brick house is measured to have an inside temperature of T = 29O K and an outside temperature of To = 320 K . Assume %3D this wall has constant thermal conductivity k = 1.5 W/(m²-K) and the temperature profile through the wall is linear. If the brick wall is 0.11 m thick, determine the total heat transfer through the wall (in Watts) if the wall has an area of 25 m².arrow_forwardHeat is lost through the glass pane of a window. The thickness of the glass is 3 mm, and the window is 0.9 m by 1.8 m. The thermal conductivity of glass is 0.8 W/mK. If the temperature difference across the glass is 17 K, what is the total heat transfer through the pane of glass? Give your answer in Watts to the nearest integer.arrow_forward1/ The roof of an electrically heated home is 6 m long, 8 m wide, and 0.25 m thick, and is made of a flat layer of concrete whose thermal conductivity is k = 0.8 W/m.°C (Figure. 1-3). The temperatures of the inner and the outer surfaces of the roof one night are measured to be 15°C and 4°C, respectively, for a period of 10 hours. Determine the rate of heat loss through the roof at nightarrow_forward
- At a temperature of 21.4°C the hole in a steel plate has an area of 8.80 x 10- m2. You heat the plate until the area of the hole increases to 8.97 x 10- m2, which allows a steel rod to just slip through this hole. What is the final temperature of the plate? The coefficient of linear expansion of steel is 12 × 10-0/°C.arrow_forwardA father and son conducted the following simple experiment on a hot dog which measured 12.5 cm in length and 2.2 cm in diameter. They inserted one food thermometer into the midpoint of the hot dog and another one was placed just under the skin of the hot dog. The temperatures of the thermometers were monitored until both thermometers read 20°C, which is the ambient temperature. The hot dog was then placed in 94°C boiling water and after exactly 2 min they recorded the center temperature and the skin temperature of the hot dog to be 59°C and 88°C, respectively. Assuming the following properties for the hot dog: r = 980 kg/m3 and cp = 3900 J/kg·K and using transient temperature charts, determine (a) the thermal diffusivity of the hot dog, (b) the thermal conductivity of the hot dog, and (c) the convection heat transfer coefficient.arrow_forwardDetermine the ratio of thermal conductivity for N2 at sea level (T = 300 K, P = 1 atm) versusthe lower stratosphere (T = 230 K, P = 0.25 atm).arrow_forward
- The author and his then 6-year-old son have conducted the following experiment to determine the thermal conductivity of a hot dog. They first boiled water in a large pan and measured the temperature of the boiling water to be 94°C, which is not surprising, since they live at an elevation of about 1650 m in Reno, Nevada. They then took a hot dog that is 12.5 cm long and 2.2 cm in diameter and inserted a thermocouple into the midpoint of the hot dog and another thermocouple just under the skin. They waited until both thermocouples read 20°C, which is the ambient temperature. They then dropped the hot dog into boiling water and observed the changes in both temperatures. Exactly 2 min after the hot dog was dropped into the boiling water, they recorded the center and the surface temperatures to be 59°C and 88°C, respectively. The density of the hot dog can be taken to be 980 kg/m3, which is slightly less than the density of water, since the hot dog was observed to be floating in water while…arrow_forwardIn a double-glazed window, the panes of glass are separated by 1.0 cm and the space is filled with a gas with thermal conductivity 24 mW K−1 m−1. What is the rate of transfer of heat by conduction from the warm room (28 °C) to the cold exterior (−15 °C) through a window of area 1.0 m2? You may assume that one pane of glass is at the same temperature as the inside and the other as the outside. What power of heater is required to make good the loss of heat?arrow_forwardA 4-mm and 2-m-long electric wire is tightly wrapped with a 2-mm-thick plastic cover whose thermal conductivity is k =0.1 W/m-°C. Electrical measurements indicate that a current of 10 A passes through the wire and there is a voltage drop of 10 V along the wire. If the insulated wire is exposed to a medium at =20 °C with a heat transfer coefficient of h=10 T. W/m2.°C, determine the temperatures T1 and T2 as shown in the figure below. Also determine whether doubling the .thickness of the plastic cover will increase or decrease T2 Tarrow_forward
- Two large steel plates at temperature of 90°C and 70°C are separated by a steel rod 2.5 cm diameter and 0.25 m long. The rod is welded to each plate. The space between the plates is filled with insulation which also insulates the circumference of the rod. Because of voltage difference between the two plates current flows through the rod and the electrical energy is dissipated at a rate of 10 W. Determine the maximum temperature in the rod and the heat flux at each end. Proceed to compare the net heat flow rate of the two ends with the total rate of heat generation. Thermal conductivity for the rod material is 42.5 W/m-deg.arrow_forwardIt is designed in such a way that the internal temperature of a commercial heat treatment furnace can reach up to 165 oC. All surfaces of the furnace consist of firebrick (10 cm), insulation material and sheet metal (3mm) from the inside out. Given that the outdoor temperature is 22 oC, the outer sheet will be allowed to go up to 35 oC, which is a temperature that will not disturb in contact with hands. In this case, determine the insulation material thickness to be used. The thermal conductivity coefficient of the insulation material is insulation 0.066 W / m oC, 60 W / m oC for sheet metal and 115 W / m oC for firebrick. Indoor heat transfer coefficient will be accepted as 25 W / m2 oC and 12 W / m2 oC for outdoor environment.arrow_forwardA 1-in Sch 40 stainless steel pipe with a thermal conductivity of 45 W/m-K can move 1,000 kg of saturated steam per hour at 150 °C. Refractory material 0.25 inches thick with a thermal conductivity of 0.025 W/m-K insulates the pipe. At a temperature of 25 °C, the pipe is exposed to the outside air. There is a 1135 W/m2 internal heat transfer coefficient.40 W/m2-K is the outside heat transfer coefficient, whereas -K. Suppose that only the radial direction is involved in steady-state heat transfer and that radiation effects are negligible. ✓ Determine how much heat is being lost through these pipes to the environment.a. 399.1 W/mb. 1525.0 W/mc. 618.4 W/md. 1128.7 W/me. none of the above √ How about the insulated pipe's surface temperature?a. 118.5 °Cb. None of the abovec. 101.5 °Cd. 216.3 °Ce. 292.2 °Carrow_forward
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