heat transfer in a non insulated house

[jayanth090909]

Hi,

As i'm new to the field of thermodynamics, I had a doubt, i wanted to know the heat transfer from outside of the wall into the room. I also wanted to know the behaviour wrt time. I know the heat transfer happens by conduction through wall, but my particular doubt was if we integrate we get some dynamics wrt outside to room heat transfer. I wanted to know that.

 

[KiwiMace]

Most of the heat transfer on non insulated buildings is driven by solar gain, rather than delta temp. Look up sol-air temp for estimation of heat gain and internal temp, but this won't get you transients without some form of model.

 

[willard3]

You should take a course in heat transfer/thermodynamics which will be available at a university near you with an Engineering school.

You're not going to learn this on a web forum.

 

[jayanth090909]

Thank you for ur reply, but if u integrate wrt to the heat transfer by conduction or convection wrt outside and room temperature , there should be some dynamics or behaviour with time. I wanted that part exactly.

 

[chicopee]

There is and the basic equation is the heat transfer in minus the heat transfer out is equal to the rate of change of the temperature.

 

[KiwiMace]

Wouldn't that be 'differentiate'?

 

[IRstuff]

"I know the heat transfer happens by conduction through wall"

That's a problem that others are trying to point out. Conduction is just the part involving the interior of the wall. Convection applies to both sides of the wall, and radiation from the sun applies to the outside of the wall, and some radiation applies to the inside of the wall.

TTFN

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[jayanth090909]

Hi ,

I know the above concepts what u told, but if u see the behaviour wrt time, there should be some plot rite. I need that wrt time not wrt thickness of the wall.

 

[MintJulep]

Heat transfer will change with the difference in temperature and solar gain.

So when it's hot outside and the sun is shining heat will go in.

When it's cold outside and dark heat will go out.

 

[LostHippie]

Heat transfer is affected by many factors...especially on the scale you are talking about:

Temperature outside
Temperature inside
Humidity outside
Air movement both outside and inside
Orientation of surfaces
Emmissivity of certain materials
Solar insolation (day)
Cloud cover (night)
structure and materials of flooring, roofing, walls, windows (shading coefficients, u factors, etc.), doors, presence of appliances and electronics...

these can all affect the RATE of heat transfer into and out of a structure, and when integrated will not yield a simple inside temperature wrt but will yield a 3 dimensional temperature vs time plot for all points within the system...and would be ridiculously complex...

simple heat transfer that you are thinking about requires a simple mathematical model, which means simplifying your current model with a lot of assumptions...a problem like this would be quite an undertaking without making assumptions, there are simply too many degrees of freedom...

 

[jayanth090909]

thank you.

 

[vpl]

This isn't the right place for you. You would be better served by going to Wikipedia. There you will find formulas and maybe even plots of heat change over time.

You might also try a Google search (though that might be what brought you here) on something like "daily and annual temperatures for [your location.]" Then create a plot for inside that reflects the outside, with some delay factor Simplistically, if you have no insulation, and no heating or cooling, then your house will basically be the outside temperature. As it heats up outside, the temperature will go up, and as it cools down outside, the temperature will go down. There is usually some delay. If you have heating or cooling then it will impact the inside temperature.

The better the insulation, the less effect the outside has on the inside (though if there is no heating or cooling, eventually there will be equilibrium with the outside, there just will be more of a delay.)

Patricia Lougheed

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