Thermal values for a double pane window

[jghlee]

Homework Statement

So there's a double pane window, where between two identical sheets of glass is air. So on the outer surface side, there 3mm of glass, then 9mm of air, and then another 3mm of glass. Outside temp is 50 degrees C and inside temp is 25 degrees C.

Heat of conductivity for glass is 0.8W/(mxK) and for air is 0.024 W/(mxk).

a) What is the total R-value for the double pane window?
b) What is the conductive heat flow rate per square meter of window area through the double pane window?

Homework Equations

R = d/k

U = 1/R

The Attempt at a Solution

a) So for part a) I dug up an equation online stating the R-value = thickness/K-value.

Since the K-values and thickness are given... I plugged it in the equation...

R = [(.006m)/(0.8W/mxK)][(.009)/(.024W/mxK)] = .00281 m^2K/w

b) But for part b I'm not sure what the "conductive heat flow rate per square meter" is...

Is it the U-value? In which cause U = 1/R so it's just the reciprocal of the answer in part a?

I'm completely lost. Any help would be great!

 

[anathema]

your response to this forum post could be:

Hello,

Great job on calculating the R-value for the double pane window! You are correct, the R-value is simply the thickness of the material divided by its thermal conductivity.

For part b, the conductive heat flow rate per square meter is the amount of heat that is transferred through the window per unit area. This can be calculated using the formula Q = U x A x (T1-T2), where Q is the heat flow rate, U is the overall heat transfer coefficient (which is equal to 1/R), A is the area of the window, and T1 and T2 are the temperatures on either side of the window.

So in this case, the conductive heat flow rate per square meter would be Q = (1/R) x A x (T1-T2). Plugging in the values given, we get:

Q = (1/0.00281 m^2K/W) x (0.009m^2) x (50-25) = 640.57 W/m^2

I hope this helps clarify things for you. Keep up the good work!