U Value

[michael7]

Please could anyone tell me the U Value of 30mm Lead. I have to put AC in a room with walls, ceiling and floors of this material.

[nike123]

http://www.engineersedge.com/properties_of_metals.htm

[frank]

Please could anyone tell me the U Value of 30mm Lead. I have to put AC in a room with walls, ceiling and floors of this material.
A single component material will not have a 'U' value, it will have a 'K' value.

A 'U' value is a combination of different materials, each having a 'K' Value, and relates to an area.

For instance, a wall, made up of an internal boundary layer, plaster layer, brick layer, insulation layer, outer brick layer and external boundary layer will have a 'U' Value.(W per metre squared per degree C difference.)(w/m2C)

Any one of the component parts will have a 'K' value.

[multisync]

You can lead a horse to water but a pencil must be lead..

[frank]

Please could anyone tell me the U Value of 30mm Lead. I have to put AC in a room with walls, ceiling and floors of this material.

30mm lead????????????

Who has got a back strong enough to lift that? :confused:

[Brian_UK]

30mm lead
:off topic: Well, you won't hear the fan bearings failing on that one :D

[nike123]

A single component material will not have a 'U' value, it will have a 'K' value.

A 'U' value is a combination of different materials, each having a 'K' Value, and relates to an area.

For instance, a wall, made up of an internal boundary layer, plaster layer, brick layer, insulation layer, outer brick layer and external boundary layer will have a 'U' Value.(W per metre squared per degree C difference.)(w/m2C)

Any one of the component parts will have a 'K' value.


I taught that 'K' Value is:


K-value

The k-value, or heat transfer coefficient, is the measured value of the heat flow which is transferred through an area of 1 m² at a temperature difference of 1 K. The units of measure are watts per square meter per temperature difference (W/m²K). K-value = energy / (area x temperature difference x time).




and U-value is:


U-value

The U-factor (or U-value), more correctly called the overall heat transfer coefficient (http://en.wikipedia.org/wiki/Heat_transfer_coefficient#Overall_heat_transfer_coefficient), describes how well a building element conducts heat. It measures the rate of heat transfer through a building element over a given area, under standardised conditions. The usual standard is at a temperature gradient of 24 °C, at 50% humidity (http://en.wikipedia.org/wiki/Humidity) with no wind[3] (http://en.wikipedia.org/wiki/R-value_%28insulation%29#cite_note-2) (a smaller U-value is better).

[taz24]

Please could anyone tell me the U Value of 30mm Lead. I have to put AC in a room with walls, ceiling and floors of this material.


With 30mm of lead as a shield I would not like to be in that room when the machine is turned on :p :p.


I have tried looking up and find no referance for lead.

I will keep on looking but I would think the thermal value of lead would be fairly high. Do your calculations with out the lead there and you will not be any worse off. If the lead has any insulation value then it will only help with the efficiency..

Cheers taz.

.

[SteinarN]

The lead itself has a K-value of 35.3W/m/K.

For a wall consisting of a 30mm thick lead sheet this gives an U-value of 1177W/m2/K.

A very poorly insulated room :rolleyes:

[Argus]

.



We’re all scratching our heads wondering why the lead has to be 30mm thick…… no doubt there is some heavy duty radiation going on.

Perhaps you’ll tell us.

In basic terms, SteinarN’s right, not allowing for surface resistance etc., the U value of lead calculated from the thermal resistance and 30mm thickness is about 1177 W/M2K. Any metal, (and lead is no exception), will provide very poor insulation value.

You then need to add the reciprocals of all K values and the total thicknesses of material behind the lead on all sides of the structure to achieve the true thermal conductivity.

I’d be paying some attention to the safety hazards of lead, too…….




.

[frank]

And give me a shout when the job is ready for demolition, as I for one, would like to be removing the lead for scrap value :D

[SteinarN]

In basic terms, SteinarN’s right, not allowing for surface resistance etc.

I know I didn't take the surface resistance into acount. The OP wasn't too detailed so I decided to do a simple calculation. I suppose there has to bee some structural components involved here also.