Consider a thin electrical heater attached to a plate and backed by insulation. Initially, the heater and plate are at the temperature of the ambient air,
(a) Sketch and label, on
(b) Sketch the heat flux at the outer surface
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Introduction to Heat Transfer
- 2.3 The shield of a nuclear reactor is idealized by a large 25-cm-thick flat plate having a thermal conductivity of . Radiation from the interior of the reactor penetrates the shield and there produces heat generation that decreases exponentially from a value of at the inner surface to a value of at a distance of 12.5 cm from the interior surface. If the exterior surface is kept at 38°C by forced convection, determine the temperature at the inner surface of the field. Hint: First set up the differential equation for a system in which the heat generation rate varies according to .arrow_forwardBoth ends of a 0.6-cm copper U-shaped rod are rigidly affixed to a vertical wall as shown in the accompanying sketch. The temperature of the wall is maintained at 93C. The developed length of the rod is 0.6 m, and it is exposed to air at 38C. The combined radiation and convection heat transfer coefficient for this system is 34W/m2K. (a) Calculate the temperature of the midpoint of the rod. (b) What will the rate of heat transfer from the rod be?arrow_forward1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4arrow_forward
- A square silicon chip 7mm7mm in size and 0.5-mm thick is mounted on a plastic substrate as shown in the sketch below. The top surface of the chip is cooled by a synthetic liquid flowing over it. Electronic circuits on the bottom of the chip generate heat at a rate of 5 W that must be transferred through the chip. Estimate the steady-state temperature difference between the front and back surfaces of the chip. The thermal conductivity of silicon is 150 W/m K. Problem 1.6arrow_forwardA 0.6-cm diameter mild steel rod at 38C is suddenly immersed in a liquid at 93C with hc=110W/m2K. Determine the time required for the rod to warm to 88C.arrow_forwardQuestion 1: A glass window of width W = 1 m and height H = 2m is 5 mm thick and has a thermal conductivity of kg =1.4 W/m.K. If the inner and outer surface temperatures of the glass are 15 °C and -20 C, respectively, on a cold winter day, what is the rate of heat loss through the glass? To reduce heat loss through windows, it is customary to use a double pane construction in which adjoining panes are separated by an air space. If the spacing is 10 mm and the glass surfaces in contact with the air have temperatures of (last two digit of your Registration number) °C and -15 °C, what is the rate of heat loss from a 1 mx2mwindow? The thermal conductivity of air is ka = 0.024 W/m.K.arrow_forward
- 4) In a tempering process, glass plate, which is initially at a uniform temperatureTi, is cooled by suddenly reducing the temperature of both surfaces to Ts Theplate is 20 mm thick, and the glass has a thermal diffusivity of 6x 10-7 m2/s.(a) How long will it take for the midplane temperature to achieve 50% of itsmaximum possible temperature reduction? Ans t= 63 s(b) If (Ti -T5) = 300°C, what is the maximum temperature gradient in the glass atthe above time? Ans. -2.36 104 °C/m.arrow_forwardA food product with 80% moisture content in a 5 cm diameter can wants to be frozen. The density of the product is 1000 kg / m cubic, the thermal conductivity is 1.0 W / (m K), and the initial freezing temperature is -1.75 ° C. After 10 hours in -25 ° C freezing medium, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinderarrow_forwardA sphere of 80 mm diameter (k=50 W/m.K and α=1.5x10-6 m2/s) is initially at a uniform, elevated temperature, and is quenched in an oil bath maintained at 30 °C. The convection coefficient for the cooling process is 1100 W/m2K. At a certain time, the surface temperature of the sphere is measured to be 120 °C. What is the corresponding center temperature of the sphere?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning