Single-Pane Window Heat Loss Equation and Calculator

Heat Transfer Engineering
Thermodynamics
Engineering Physics

Heat Loss through a Single-Pane Window Equation and Calculator

Heat Loss through a Single-Pane Window Equation and Calculator

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Preview: Heat Loss Through a Single-Pane Window Calculator

Heat Loss Equation

R Total

R Glass

R Conv1

R Conv2

Where:

Q = Heat Steady State Transfer (W)
A = Area (m2)
k = Thermal Conductivity (W/m · °C)
T∞1 = Temperature (°C)
T∞2 = Temperature (°C)
h1 = Heat Transfer Coefficient (W/m2 · °C)
h2 = Heat Transfer Coefficient (W/m2 · °C)
Rconv, 1 = Thermal Resistance (°C/W)
Rconv, 2 = Thermal Resistance (°C/W)
Rglass = Thermal Resistance Glass (°C/W)

Example:

0.8-m-high and 1.5-m-wide glass window with a thickness of 8 mm and a thermal conductivity of k = 0.78 W/m · °C. Determine the steady rate of heat transfer through this glass window and the temperature of its inner surface for a day during which the room is maintained at 20°C while the temperature of the outdoors is -10°C. Take the heat transfer coefficients on the inner and outer surfaces of the window to be h1 = 10 W/m2 · °C and h2 = 40 W/m2 · °C, which includes the effects of radiation.

Assumptions

1 Heat transfer through the window is steady since the surface temperatures remain constant at the specified values.
2 Heat transfer through the wall is one-dimensional since any significant temperature gradients will exist in the direction from the indoors to the outdoors.
3 Thermal conductivity is constant.

R Glass, Ri, Ro

all three resistances are in series, the total resistance is

Total Resistance

steady rate of heat transfer through the window becomes

Steady HEat Transfer

Knowing the rate of heat transfer, the inner surface temperature of the window glass can be determined from

Surface Temperature

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