Problem with the dynamic radiator system

["Richard Heimrath" <heimrath@xxxxxxxxxxxxxxxxx>]

Hallo everybody !

I have a problem with the combination from the Type 56 (building) and the
Types 162 and 120 (radiator and PID controller).

If I use very small time steps in my .dck (> 1/16 ) and also a
convergence and integration under 0.01, the building is getting room
temperatures over 100 °C and more. 

Attached you find the part of my .dck with the Types 162 and 120. 

If you have some experience on this problem, please help me.

Thanks in advance,

Richard

---

Richard Heimrath
Institute of Thermal Engineering
Graz University of Technology, Austria
Inffeldgasse 25, A-8010 Graz
E-mail: heimrath@iwt.tu-graz.ac.at
IWT-Homepage: http://wt.tu-graz.ac.at

* Just for example !!

   cpwat=4.19
   trset=20
   tambd= design ambient temperature
   Tind= design flow temperature
   Toutd= design return pipe temperature
*  Nominal heating power of radiator
   Pd=(20-tambd)*QStand/30
*  mdot max kg/h
   mdot80=Pd/(cpwat*(tind-toutd))
*  ftemp faktor Qnorm -> Qreal
   ftemp=(60/((tind+toutd)/2-20))**1.3
*  ftemp * max heat rate kJ/h
   Qnre=ftemp*Pd

*  Radiator thermal capacitance [kJ/K] * Number of App.
   CAPA=1150*NAPP
*  Mass flow control output 1 (Type 120) * controlvalue heating pump
   MFC=[43,1]*(1-in_pumph)

*  Outputs from the Type 162 prepared for the Type 56 (as radiativ and convective Gains)
   Prad  = [42,11]*[42,5]
   Pconv= [42,5]-Prad


*--------------------------------------------------------------------------*
*	Type 162 dynamic radiator
*
UNIT 42 TYPE 162 
PARAMETERS 12
* 1) XL1   : Length of supply pipe 1 [m]
0.0
* 2) XL2   : Length of exhaust pipe 2 [m]
0.0
* 3) DIAM  : Pipe diameter [m]
0.056
* 4) HV    : Horizontal(>=0) or vertical (else) pipe [-]
1
* 5) EPSI  : Emission coefficient for outer surface [-]
0.93
* 6) CW    : Specific heat of fluid [kJ/kg/K]
cpwat
* Radiator Section :
* 7) XMFRMA: Maximum mass flow rate [kg/h]
mdot80
* 8) SN    : Radiative fraction of total emitted power
*            at nominal conditions (DT=60) [-]
0.35
* 9) QN    : Nominal power of radiator (DT=60) [kJ/h]
Qnre
*10) XN    : Radiator exponent (convection+radiation) [-]
1.3
*11) CAPA  : Radiator thermal capacitance [kJ/K] MFH 5*1150 !
CAPA
*12) TIRAD : Initial radiator temperature [øC]
55
INPUTS 3
* 1 Supply fluid temperature --- Input from the Type 11 (flow diverter)
2,1
* 2 Inside room temp. (star node temp -- type 56)
18,5
* 3 Mass flow control
MFC
*** INPUT  VALUES
* 1  2  3
  50 20 0

* TRACE 110 140
*-----------------------------------------------------------------

UNIT 43   TYPE 120
PARAMS 7
* 1  Width of PID-band (+- Delta T [K] )
        3
* 2  Proportional gain in PID-band 0.2 0.8
        0.1
* 3  Integral gain in PID-band 0.05
        0.7
* 4  Differential gain in PID-band 0.0
        0.0
* 5  Proportional gain in P-band 0.5
        0.5
* 6  Controller mode;-2:free -1:->-1+1,0:Smin+1
        0
* 7  minimum value of total control action ... Smin=0 for 0 to +1
        0

INPUTS 3
* 1  Setting value Not Connected. Fix value (trset=20°C)
        trset
* 2  Inside room temperature..from.. Type 56 (Air temp. !)
        18,1
* 3  Control inversion option (1 or 2) Not Connected. Fix value
        0,0

*  INPUT INITIAL VALUES
* 1    2    3
  20   20   2
*--------------------------------------------------------------------------*
UNIT 2 TYPE 11 DIV-HOUS
PARAMETERS 1
* 1 Controlled flow diverter mode
2
INPUTS 3
* 1 Inlet temperature
38,1
* 2 Inlet flow rate
38,2
* 3 Control signal 24,2
in_pumph
*** INPUT  VALUES
30 3600 0

*--------------------------------------------------------------------------*
UNIT 26 TYPE 11 MIX_HOUS
PARAMETERS 1
* 1 Tee piece mode
1
INPUTS 4
* 1 Temperature at inlet 1
42,1
* 2 Flow rate at inlet 1
2,2
* 3 Temperature at inlet 2
3,1
* 4 Flow rate at inlet 2
3,2
*** INPUT  VALUES
20 3600 20 0

*--------------------------------------------------------------------------*