How Do I Calculate Heat Transfer Through a Multi-Layered Ceiling?

In summary, the problem is that you need to calculate the heat transfer through a series of resistors, and you don't know how to do it.
  • #1
Ziga Casar
4
0
Hello guys,

I have a problem and I don't know how to solve it properly ...

So I have this situation:
armstrongplosca.png

And I must calculate the heat transfer (Q) through it ...

I know that the Indoor Temperature is 21C and the outdoor Temperature is 0C, I also know the following data for all layers:
Concrete: d (thickes) = 0.4m, k (Thermal conductivity) = 1.10 W/mK
Air: d = 2.25m, k = 0.0244 W/mK
Armstrong plate: d = 0.015m, k = 0.06 W/mK

And the surface is S = 731.9 m^2

I know I should calculate through this expression: Q = U S (T1-T2) and 1/U = SUM(d/k) = SUM(1/alpha)

the sum of d/k is no problem but for sum of 1/alpha, I do not know hot to calculate the alphas (Convection coefficient), because there is one alpha from air to Armstrong and one alpha from concrete to air (Or are there 2 alphas for each because the temperature under Armstrong plate is higher that the temperature above the Armstrong plate ...?)

So here is the problem, because there is a natural motion of air and a big horizontal plate I do not know hot to calculate the alphas... Can somebody please help me?
 
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  • #2
You need to concentrate on what the variables represent - and think: resistors in series.
 
  • #3
I do not exactly understand what you mean. Can you explain it a little bit better?
 
  • #4
How would you find the current through resistors in series?
Now: heat flow = current, temperature difference voltage.
 
  • #6
I completely understand the resistance circuits. But when I calculate the heat flux through the concrete only I get 42 253W, but when I calculate the heat flux through concrete, air and plate I get 165.5W. But this is only conduction, in real there is there also convection, and for convection I need alphas ... or is it not important to consider convection by calculating the heat flow?

I mean the heat flux difference is huge. I can not imagine that if you lower a ceiling with this plates you safe so much of energy? Air is a good isolator, but so good?
 

FAQ: How Do I Calculate Heat Transfer Through a Multi-Layered Ceiling?

1. How does heat transfer through a ceiling?

Heat transfer through a ceiling occurs through three main processes: conduction, convection, and radiation. Conduction is the transfer of heat through a solid material, such as the ceiling itself. Convection is the transfer of heat through a fluid, such as air, as it circulates through the room. Radiation is the transfer of heat through electromagnetic waves, which can pass through the ceiling and warm the space below.

2. What factors affect heat transfer through a ceiling?

The rate of heat transfer through a ceiling can be influenced by several factors, including the temperature difference between the ceiling and the surrounding space, the thermal conductivity of the ceiling material, the presence of insulation, and the air circulation within the room.

3. How can I reduce heat transfer through my ceiling?

To reduce heat transfer through a ceiling, you can improve insulation by adding more insulation materials, sealing any air leaks, and installing reflective barriers. You can also reduce air circulation by keeping doors and windows closed, using ceiling fans to circulate air, and using curtains or blinds to block direct sunlight.

4. Can heat transfer through a ceiling impact my energy bills?

Yes, heat transfer through a ceiling can have a significant impact on your energy bills. If your ceiling is not well insulated, heat can escape in the winter, causing your heating system to work harder and use more energy. In the summer, heat can enter through the ceiling, making your air conditioning work harder and increasing your energy costs.

5. Are there any safety concerns related to heat transfer through a ceiling?

There are potential safety concerns related to heat transfer through a ceiling, particularly if the ceiling is not well insulated. In the winter, the warm air from your heating system can rise and come in contact with a cold ceiling, causing condensation and potentially leading to mold growth. In the summer, heat entering through the ceiling can make your home uncomfortable and potentially lead to heat-related illnesses.

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