If a heat transfer coefficient of 2.84 W l(m2 • K) exists on each of the two inside faces of two sheets of 6.35-mm-thick glass separated by an air gap, calculate the gap that can be used such that the rate of heat transfer by conduction through the air gap equals the rate of heat transfer by convection. What is the rate of heat transfer if this gap is exceeded. The thermal conductivity of air of 0.0242 WI (m . K). Solve for temperature of 20°C and 12°C on the outside surfaces of the glass. Would the calculated gap change in value for different values of the surface temperatures? Would there be any advantage to increasing the gap beyond this calculated value?

If a heat transfer coefficient of 2.84 W l(m2 • K) exists on each of the two inside faces of two sheets of 6.35-mm-thick glass separated by an air gap, calculate the gap that can be used such that the rate of heat transfer by conduction through the air gap equals the rate of heat transfer by convection. What is the rate of heat transfer if this gap is exceeded. The thermal conductivity of air of 0.0242 WI (m . K). Solve for temperature of 20°C and 12°C on the outside surfaces of the glass. Would the calculated gap change in value for different values of the surface temperatures? Would there be any advantage to increasing the gap beyond this calculated value?

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...

See similar textbooks

Similar questions

1.1 On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to temperature of –5°C, while the inner surface is kept at 20°C. The thermal conductivity of the concrete is 1.2 W/m K. Determine the heat loss through the wall, which is 10-m long and 3-m high. Problem 1.1
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
1.11 Calculate the heat loss through a glass window 7-mm thick if the inner surface temperature is 20°C and the outer surface temperature is 17°C. Comment on the possible effect of radiation on your answer.
One end of a 0.3-m-long steel rod is connected to a wall at 204C. The other end is connected to a wall that is maintained at 93C. Air is blown across the rod so that a heat transfer coefficient of 17W/m2 K is maintained over the entire surface. If the diameter of the rod is 5 cm and the temperature of the air is 38C, what is the net rate of heat loss to the air?
2.51 Determine by means of a flux plot the temperatures and heat flow per unit depth in the ribbed insulation shown in the accompanying sketch.
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
A 1 in. o.d. (outer diameter) tube reactor is insulated with a 3 inch layer of asbestos. If the temperature of the outer surface of the insulation is 100 °F and the rate of heat loss per foot of reactor length is 50 BTU/hr, what must the temperature of the inside of the reactor be? [for asbestos, k = 0.105 BTU/hr ft °F]
What is thermal conductivity? How the thermal conductivity of Solid, liquid and gases are varying with temperatures and pressure? Explain the variation of thermal conductivity of metals and non-metals with temperatures?
In 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.
In 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).
Answer within 10 minutes : The temperature at the inside surface of an oven is 460 oF. The inside wall of the oven is made of brick and is 8 inch thick. The thermal conductivity of the brick is 2.2 Btu/hr.ft2.(oF/ft). The outside of the oven is covered with a 3-inch layer of asbestos as insulation, which has a thermal conductivity of 0.11 Btu/hr.ft2.(oF/ft). If the outer surface of the insulation has a temperature of 100 oF , calculate the amount of heat lost through 2 ft2 of wall area in 3 hours.
Question 1.2:Consider heat loss through the two walls of a house on a winter night. The walls are identical, except that one of them has a tightly fit glass window. Through which wall will the house lose more heat? Explain. (03)