A thermopane window consists of two pieces of glass The window separates room air at 20°C from outside ambient air at -10°C. The convection coefficient associated with the inner (room-side) surface is 10 W/m²K. If the convection coefficient associated with the outer (ambient) air is ho 80 W/mK, what is the heat loss through a window that is 0.8 m long by 0.5 m wide? Neglect radiation, and assume the air enclosed between the panes to be stagnant. Take glass thermal conductivity K-1.4 W/m.K, air thermal conductivity K,-0.0245 W/m.K [3.

A thermopane window consists of two pieces of glass The window separates room air at 20°C from outside ambient air at -10°C. The convection coefficient associated with the inner (room-side) surface is 10 W/m²K. If the convection coefficient associated with the outer (ambient) air is ho 80 W/mK, what is the heat loss through a window that is 0.8 m long by 0.5 m wide? Neglect radiation, and assume the air enclosed between the panes to be stagnant. Take glass thermal conductivity K-1.4 W/m.K, air thermal conductivity K,-0.0245 W/m.K [3.

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 1.4P: 1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus...

See similar textbooks

Similar questions

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 .
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
1.63 Liquid oxygen (LOX) for the space shuttle is stored at 90 K prior to launch in a spherical container 4 m in diameter. To reduce the loss of oxygen, the sphere is insulated with superinsulation developed at the U.S. National Institute of Standards and Technology's Cryogenic Division; the superinsulation has an effective thermal conductivity of 0.00012 W/m K. If the outside temperature is on the average and the LOX has a heat of vaporization of 213 J/g, calculate the thickness of insulation required to keep the LOX evaporation rate below 200 g/h.
The rear window of an automobile is defogged by passing warm air over its inner surface. If the warm air is at T∞,i=40°C and the corresponding convection coefficient is hi=30 W/m2·K, what are the inner and outer surface temperatures, in °C, of 4-mm-thick window glass, if the outside ambient air temperature is T∞,o= -15°C and the associated convection coefficient is ho=65 W/m2·K? Evaluate the properties of the glass at 300 K. a. What is the Ts, i at °C? b. What is the Ts, o at °C?
The rear window of an automobile is defogged by passing warm air over its inner surface. If the warm air is at T∞,i=40°C and the corresponding convection coefficient is hi=30 W/m2·K, what are the inner and outer surface temperatures, in °C, of 4-mm-thick window glass, if the outside ambient air temperature is T∞,o= -27.5°C and the associated convection coefficient is ho=65 W/m2·K? Evaluate the properties of the glass at 300 K. a. what is the heat flux through the original walls in W/ m^2? b. what is the heat flux through the retrofitted walls in w /m^2?
Question One Explain how heat is transferred from one point to another illustrating with appropriate diagram. Calculate the heat flow per square meter (heat flux) through water medium with thermal conductivity of 0.6, flowing in a 5 cm thickness space, if the temperatures on the two surfaces are 50 and 210°C, respectively. Question 2 Distinguish between force and free convection with the aid of appropriate illustrations. What is the approximate temperature difference between a hot plate and the surrounding air if the heat flux from the plate is 800 W/m2? Assume that the air is flowing past the surface with a velocity of 5 m/s giving a heat transfer coefficient of 20 W/(m2K). Question 3 Explain the differences between laminar and turbulent flow Water (ν = 0.86x10-6m2/s) flows through a tube with the diameter 12 mm at a velocity of 2 m/s. Determine if the flow is laminar or turbulent!
A spherical thin walled metallic container is used to store liquid nitrogen at 72 K . The container has a diameter of 0.5 m and is covered with an evacuated, reflective insulation composed of silica powder. The insulation is 29 mm thick and its outer surface is exposed to ambient air at 301 K. The convection coefficient is known to be 24 W/m2 K. What is the rate of heat transfer to the liquid nitrogen (Enter the answer in W correct up to 3 decimal places)? Take the thermal conductivity k of evacuated silica powder is 0.0017 W/m K .
An insulated steam pipe passes through a room in which the air and walls are at 25°C. The outside diameter of pipe is 70 mm, and its surface temperature and emissivity are 200°C and 0.80, respectively. If the free convection coefficient from the surface to the air is 15 W/m2-K, what is the rate of heat loss from the surface per unit length of pipe?
Question 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.
Natural Convection Cooling of an Orange.An orange 102 mm in diameter having a surface temperature of 21.1°C is placed on an open shelf in a refrigerator held at4.4°C. Calculate the heat loss by natural convection, neglecting radiation. As an approximation, the simplified equation for vertical planes can be used withLreplaced by the radius of the sphere (M1). For a more accurate correlation, see (S2).
Read the question carefully and give me right solution according to the question. A solid copper sphere (k = 393 W/mK), 10 mm in diameter, initially at 800C is placed in an air stream at 300 C. The temperature is dropped to 650C after 61 seconds. Calculate the value of convection coefficient. Assume properties as ρ= 8925 kg/m3, C = 397 J/kg K.
Sketch the temperature distribution in wedge below along the centreline, showing your reasoning andproper equations used. assuming a uniform thermal conductivity and a temperature of 122 °C on the rightface, and 22 °C on the left face. The top and bottom faces are insulated and the solid is long in the direction of the page.