A thin, disk-shaped silicon water of diameter 20cm on a production line must be maintained at a temperature of 100 degree celcius. The wafer loses heat to the room byconvection and radation from its upper surface, while heat is supplied at a constant flux from below. The surrounding air is at 20 degree C while all surrounding surfaces can be approximated to be isothermal at a temperature of 15 degree C. The wafer to air heat transfer coefficient is 30W/m^2-K and the emisivity of the wafer’s surface (approximate as graybodies) is 0.85. How much heat must be applied to the wafer at the unit of W?

A thin, disk-shaped silicon water of diameter 20cm on a production line must be maintained at a temperature of 100 degree celcius. The wafer loses heat to the room byconvection and radation from its upper surface, while heat is supplied at a constant flux from below. The surrounding air is at 20 degree C while all surrounding surfaces can be approximated to be isothermal at a temperature of 15 degree C. The wafer to air heat transfer coefficient is 30W/m^2-K and the emisivity of the wafer’s surface (approximate as graybodies) is 0.85. How much heat must be applied to the wafer at the unit of W?

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.18P: The heat transfer coefficient for a gas flowing over a thin float plate 3-m long and 0.3-m wide...

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1.4 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 1.4
2.45 Heat is transferred from water to air through a brass wall . The addition of rectangular brass fins, 0.08 cm thick and 2.5 cm long, spaced 1.25 cm apart, is contemplated. Assuming a water-side heat transfer coefficient of and an airside heat transfer coefficient of , compare the gain in heat transfer rate achieved by adding fins to (a) the water side, (b) the air side, and (c) both sides. (Neglect temperature drop through the wall.)
The heat transfer coefficient for a gas flowing over a thin float plate 3-m long and 0.3-m wide varies with distance from the leading edge according to hc(x)=10x1/4Wm2K If the plate temperature is 170C and the gas temperature is 30C, calculate (a) the average heat transfer coefficient, (b) the rate of heat transfer between the plate and the gas, and (c) the local heat flux 2 m from the leading edge. Problem 1.18
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