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Re: [EnergyPlus_Support] A question about CTFs
Here is a code which I wrote in VBA to bring in CTFs from Excel along with inside and outside surface temperatures, and can then calculate the new heat flux. I have an expanded version which performs surface heat balances so that you do not have to bring in surface temperatures, but I figured this is focused more on what you were wanting. Hope it helps in some way.
Sub CTFtoFlux()
'Calculates hourly flux values for a given day using CTFs up to order n=5
'Dimension Variables
'X(n),Y(n),Z(n),PHI(n),Text(day, hour),Tint(day, hour),
'days, hours
Dim qflux_in(8761) As Single, Text(8761) As Single, Tint(8761) As Single
Dim X(7) As Single, Y(7) As Single, Z(7) As Single, PHI(7) As Single
'*******Read in CTFs
Xflag = 0: Yflag = 0: Zflag = 0: PHIflag = 0
For i = 0 To 7
If Xflag = 0 Then
If IsEmpty(Cells(i + 6, 3)) = False Then
X(i) = Cells(i + 6, 3).Value
Else
n_X = i - 1
Xflag = 1
End If
End If
If Yflag = 0 Then
If IsEmpty(Cells(i + 6, 4)) = False Then
Y(i) = Cells(i + 6, 4).Value
Else
n_Y = i - 1
Yflag = 1
End If
End If
If Zflag = 0 Then
If IsEmpty(Cells(i + 6, 5)) = False Then
Z(i) = Cells(i + 6, 5).Value
Else
n_Z = i - 1
Zflag = 1
End If
End If
If PHIflag = 0 Then
If IsEmpty(Cells(i + 6, 6)) = False Then
PHI(i) = Cells(i + 6, 6).Value
Else
n_PHI = i - 1
PHIflag = 1
End If
End If
Next i
'*******Input Daily Temp Range
For days = 1 To 364
For hours = 1 To 24
HRofYR = 24 * days + hours
Text(HRofYR) = Cells(hours + 18, 3)
Tint(HRofYR) = Cells(hours + 18, 4)
Next hours
Next days
'*******Initial (day zero) Heat Flux set to zero
For hours = 1 To 24
qflux_in(hours) = 0
Next hours
'******Calculate fluxes for three days, check for convergence
For days = 1 To 3
For hours = 1 To 24
HRofYR = 24 * days + hours
'**************interior: qcond=Z0term-Zsum+Y0term+Ysum+PhiSum
zTerm = Z(0) * Tint(HRofYR)
'Sum up Z terms (inside temperature terms)
zSum = 0
For k = 1 To n_Z
zSum = zSum + Z(k) * Tint(HRofYR - k)
Next k
yTerm = Y(0) * Tint(HRofYR)
'Sum up Y terms (outside temperature terms)
ySum = 0
For k = 1 To n_Y
ySum = ySum + Y(k) * Text(HRofYR - k)
Next k
'Sum up flux history terms
phiSum = 0
For k = 1 To n_PHI
phiSum = phiSum + PHI(k) * qflux_in(HRofYR - k)
Next k
qflux_in(HRofYR) = -zTerm - zSum + yTerm + ySum + phiSum
Next hours
Next days
'*****************exterior: qcond=-Y0term-Ysum+X0term+Xsum+PhiSum
'*****************Output flux data
For days = 1 To 3
For hours = 1 To 24
HRofYR = 24 * days + hours
Cells(9 + hours, days + 8) = qflux_in(HRofYR)
Next hours
Next days
End Sub
----- Original Message ----
From: wanglei <wangleihello@xxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Monday, October 22, 2007 9:11:16 PM
Subject: [EnergyPlus_Support] A question about CTFs
Dear all:
I want to use the CTF to calculate the heat transfer through the wall.
The form of the conduction transfer function solution is below equation:
Current Inside Conductive Flux = (Inside Term 0) * (Current Inside Face Temperature)
+(Inside Term 1) * (Previous Inside Face Temperature)
+(Inside Term 2) * (Inside Face Temperature 2 Time Steps Ago)
+(Inside Term 3) * (Inside Face Temperature 3 Time Steps Ago)
+ ...
+(Cross Term 0) * (Current Outside Face Temperature)
+(Cross Term 1) * (Previous Outside Face Temperature)
+(Cross Term 2) * (Outside Face Temperature 2 Time Steps Ago)
+(Cross Term 3) * (Outside Face Temperature 3 Time Steps Ago)
+ ...
+(Flux Term 1) * (Previous Inside Face Flux)
+(Flux Term 2) * (Inside Face Flux 2 Time Steps Ago)
+(Flux Term 3) * (Inside Face Flux 3 Time Steps Ago)
+ ...
and I get the CTFs in *.eio file, the value of CTFs is shown below:
Construction, EXTERWALL1_ CONCRETE_ 2100, 4, 18, 0.167, 0.6033 , 0.900, 0.900, 0.700, 0.700,Rough
Material,SLUSH MORTAR, 0.0200, 0.930, 1800.000, 1062.000, 0.2151E-01
Material,EPS1, 0.0500, 0.040, 15.000, 1400.000, 1.250
Material,CONCRETE1_ 2100, 0.2000, 1.280, 2100.000, 920.000, 0.1562
Material,LIME MORTAR, 0.2000, 0.870, 1700.000, 1050.000, 0.2299
CTF,18,0.15049167E- 07,-0.21682487E- 18,0.67069711E- 13, -0.15626633E- 14
CTF,17,-0.26448243E -05,-0.15318301E -18,-0.66319653E -07, 0.15918648E- 08
CTF,16, 0.15333157E- 03,0.16905925E- 18, 0.94242000E- 05, -0.22710729E- 06
CTF,15, -0.44145301E- 02,-0.84324973E- 17, -0.39650340E- 03, 0.96432515E- 05
CTF, 14,0.76655816E- 01, 0.12202644E- 14, 0.87375554E- 02, -0.21485780E- 03
CTF, 13, -0.88895541, 0.91721351E- 13, -0.12139338 , 0.30224184E- 02
CTF, 12, 7.3048382 , 0.37306641E- 11, 1.1614489 , -0.29318711E- 01
CTF, 11, -44.119610, 0.64830792E- 10, -8.0375559 , 0.20599150
CTF, 10, 200.43401 , 0.56642175E- 09, 41.419788 , -1.0792574
CTF, 9, -694.62120 ,0.25311226E- 08, -161.69510 , 4.2897295
CTF, 8, 1849.9195 ,0.60119969E- 08, 482.45677 , -13.050737
CTF, 7, -3792.0595 , 0.74054537E- 08, -1102.8340 , 30.461354
CTF, 6, 5958.2866 , 0.47728248E- 08,1923.9766, -54.337180
CTF, 5, -7099.4379 , 0.13441164E- 08, -2534.5777 , 73.285778
CTF, 4, 6290.1754 , 0.27272593E- 09, 2472.3625 , -73.274261
CTF, 3, -4008.4518 , -0.53020291E- 10, -1727.2414 , 52.524960
CTF, 2, 1733.9872 , 0.29931675E- 10, 815.66186 , -25.472846
CTF, 1, -455.33483 , -0.87445859E- 11,-232.84147 , 7.4729689
CTF, 0, 54.733855 , 0.11687668E- 11, 30.301279
The C languange source code of my program is shown below:
for(t=0;t<TotalNum; t++)
{
ZTi=0;
YTo=0;
Qqi=0;
for(j=1;j<=N; j++)
{
if(t-j>=0)
{
ZTi=ZTi+Z[j] *TI[t-j];
YTo=YTo+Y[j] *TO[t-j];
Qqi=Qqi+Q[j] *QI[t-j];
}
}
QI[t]=0-Z[0] *TI[t]-ZTi+ Y[0]*TO[t] +YTo+Qqi;
// printf("%f\t% f\t%f\n", -Z[0]*TI[ t],-ZTi,YTo, ,Qqi);
}
After run this program, the result confuses me, because the heat flue is increasing with time increasing.
Anyone can told me why?
Wang Lei
[Non-text portions of this message have been removed]
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