- #1

- 14

- 0

- Thread starter Futsal1st
- Start date

- #1

- 14

- 0

- #2

Mapes

Science Advisor

Homework Helper

Gold Member

- 2,593

- 20

If the window is a uniform single material, then that material's thermal conductivity is essentially the U factor multiplied by its thickness (ignoring convective effects). But usually windows have internal structure, multiple panes with air gaps, etc., that make the U factor more convenient to use in practice than the thermal conductivity.

- #3

- 14

- 0

- #4

Mapes

Science Advisor

Homework Helper

Gold Member

- 2,593

- 20

No, that doesn't follow. Check the units: W mSo is thermal conductivity multipied by the area of the surface the U Factor (or close as damn to it)?

- #5

- 14

- 0

So is it divide by a unit depth (I assume 1000mm) and multiply by area?

- #6

Mapes

Science Advisor

Homework Helper

Gold Member

- 2,593

- 20

What is "it"?So is it divide by a unit depth (I assume 1000mm) and multiply by area?

- #7

russ_watters

Mentor

- 19,946

- 6,436

They are just inverses of each other.

- #8

- 14

- 0

So is thermal conductivity divide by a unit depth (I assume 1000mm) and multiply by area = U factor?

- #9

- 4

- 0

In chemeng, U is used as a bundling of (various) heat transfer resistances.

Q= U*A*DT

U can be composed of heat transfer resistances due to conduction of various layers of materials and convection eg representing a building wall as inside surface convection, brick/plaster conduction, insulation conduction, and external convection...etc.

U need basic ht trfr understanding - read a basic text on heat transfer.

- #10

sophiecentaur

Science Advisor

Gold Member

- 25,200

- 4,824

I did this once when estimating how much heating I'd need in my home but ignored to add the losses due to air exchange. I couldn't believe how small the room radiators would need to be. Then I thought again and got a much higher answer. The man who came to give me an estimate for the job just looked and came up with virtually the same figure I'd spent ages calculating.

- #11

- 56

- 0

- #12

russ_watters

Mentor

- 19,946

- 6,436

Whoops, sorry, I was thinking R-value was the same as thermal conductivity. Gotta read better...

- Last Post

- Replies
- 4

- Views
- 6K

- Replies
- 2

- Views
- 2K

- Replies
- 6

- Views
- 2K

- Last Post

- Replies
- 2

- Views
- 7K

- Last Post

- Replies
- 1

- Views
- 4K

- Replies
- 3

- Views
- 1K

- Replies
- 1

- Views
- 4K

- Last Post

- Replies
- 8

- Views
- 3K

- Last Post

- Replies
- 1

- Views
- 9K

- Replies
- 1

- Views
- 2K