Re: [EnergyPlus_Support] U-values for constructions

On 16 July 2012 22:08, Linda Lawrie <linda@xxxxxxxxxxxxxx> wrote:

they are calculated dynamically throughout the simulation in EnergyPlus.

I searched for "film coefficients" in the documentation -- there are 66 instances in 7 documents.

Suggest that you read those findings.

At 01:17 PM 7/16/2012, Nacho Gomis wrote:

Back to the film coefficients, where can I find the values? I found in my notes that they depends on direction and type of air movement(downwards, upwards, horizontal and outdoor/indoor). Which values use EnergyPlus?
The U-value w/o film coefs is calculated following the tipical equation:
U=1/(R1+...+Rn)
n=number of layers in the construction
The U-value with film coefs adds them to the former ecuation but I don't know which values EnergyPlus is using.
Thanks,
Ignacio Gomis

On 16 July 2012 20:35, Nacho Gomis <nachogo27@xxxxxxxxx> wrote:

Thanks Dru, it is easier to check them in that way.

On 16 July 2012 17:33, Dru Crawley <dbcrawley@xxxxxxxxx> wrote:

An easier way to view the U-values are in the Summary Reports. Add this object to your input:

Output:Table:SummaryReports,EnvelopeSummary;

(or if you want more summary info: Output:Table:SummaryReports,AllSummaryAndMonthly; )

On Mon, Jul 16, 2012 at 10:12 AM, Ignacio <nachogo27@xxxxxxxxx> wrote:

Hello group,

I was looking for the U-value for my constructions, I think I found them in the eio file,the next lines are the headers where I found them:

! <HeatTransfer/Shading/Frame/Divider_Surface>,Surface Name,Surface Class,Base Surface,Construction/Transmittance Schedule,Nominal U (w/o film coefs)/Min Schedule Value,Nominal U (with film coefs)/Max Schedule Value,Solar Diffusing,Area (Net),Area (Gross),Area (Sunlit Calc),Azimuth,Tilt,~Width,~Height,Reveal,<ExtBoundCondition>,<ExtConvCoeffCalc>,<IntConvCoeffCalc>,<SunExposure>,<WindExposure>,ViewFactorToGround,ViewFactorToSky,ViewFactorToGround-IR,ViewFactorToSky-IR,#Sides

! <Units>,,,,,{W/m2-K}/{},{W/m2-K}/{},{},{m2},{m2},{m2},{deg},{deg},{m},{m},{m},,,,,,,,,,

So I understood that the U-values are the "Nominal U (w/o film coefs)" and "Nominal U (with film coefs)". The problem is that I dont understand very well the difference between with and without film coefs (probably I have a gap in my mind about heat transfer). Which is used to solve the heat transfer equations? Could someone help me?

Ignacio Gomis