AW: convergence problem

If you change the ventilation depending on the room temperature you will normally need a TYPE 2 Controller to achieve convergence.

That is why we added the internal solver in TYPE 56 for TRNFLOW to calculate airflows temperature depending.

Also a smaller time step might help.

with kind regards,

your TRNSYS Hotline Team

T.Welfonder, M.Rudolph

Mailto:Hotline@transsolar.com; http://www.transsolar.com

--------------------------------------------------------------------------------------------------------------------

TRNSYS - course 1 : Introduction into the work with TRNSYS

Basics for dynamic simulations

generating systems with IISiBat (solar system for domestic hot water)

10. + 11. November 2003

Price: € 900,- per person, + VAT

--------------------------------------------------------------------------------------------------------------------

TRNSYS - course 2 : Building Simulations with TRNSYS

Input of building data in PREBID

Modelling of heating, cooling and control systems in IISIBAT

how to do checking of the results

(for experienced TRNSYS-users, or participants of course 1)

26. + 27. November 2003

Price: € 900,- per person, + VAT

--------------------------------------------------------------------------------------------------------------------

TRNSYS - course 4 : airflow simulation in buildings TRNFLOW

Theory and Basics

introduction into the module TRNFLOW

Integration of TRNFlow in TRNSYS 15

available TRNFlow airflow components

Outputs of TRNFLOW

Example

adding the different TRNFLOW components to an existing multi zone model of a office with double facade

changes in the TRNSYS input file for TRNFLOW simulations

making different simulation

hints and checking of the results

(for experienced TRNSYS-users, or participants of course 2)

28. November 2003

Price: € 650,- per person, + VAT

--------------------------------------------------------------------------------------------------------------------

Information about TRNFLOW can be found at: http://www.transsolar.com/ts/indexflo.htm.

if you need any further information please contact hotline@transsolar.com.

-----Ursprüngliche Nachricht-----
Von: Laurent Serres [mailto:laurent.serres@univ-rennes1.fr]
Gesendet: Donnerstag, 25. September 2003 13:57
An: trnsys@relay.doit.wisc.edu
Betreff: Re: convergence problem

Some solutions (perhaps you have already try some of them!):

1- Add a trace statement to the unit which don't converge. You will see if there is no convergence, or a too slowly convergence, or if the input take alternatively two values (for example 1.3, then 1.4, then 1.3, then 1.4, ....)

2- you can try to increase the convergence tolerance (control cards)

3- you can try to increase the number of iterations before having an error message (control cards, "before 'WARNINGS' " and/or "before 'ERRORS', see more))

4- you can try to introduce an under-relaxation formulation in your equation card

I hope it can help you (and you understand my poor english!)

Best regards

Laurent

----- Original Message -----

From: Marco Sangiorgi

To: Trnsys

Sent: Thursday, September 25, 2003 1:07 PM

Subject: convergence problem

This process is for cooling a multi-zone building, and it is referred to one zone (repeated once for each zone with different parameters).

1.      I have a dry bulb temperature T and a Humidity Ratio HR for each zone (type 56)

2.      I mix a certain amount of air of the building with outside air (Type 9)

3.      I cool the air mix with an Heat Exchanger (Type 55)

4.      I blow the cooled air mix to the building

q       The psychrometrics and the Equations are just for certain calculations of condensations.

q       I set the FLOW of cool water that flows througth the Heat Exchanger (Type 55) to keep the temperature T of the building within a certain range

This seems easy and sometimes it works fine, but most of times I get errors (I’d reather say “horrors”) like THE INPUTS TO UNITS xx xx xx etc WERE NOT CONVERGED WITHIN THE SPECIFIED TOLERANCE AT TIME =   xx

I don’t know how to deal with it. I tried with both solvers, with the NOCHECK statement, with the backsolving technique, but as I’m not an expert I can’t achieve the convergence.

Referred to the Heat exchanger (Type 55), If I try to control the outlet temperature of the hot side (the air I need to cool) changing the flow of the cold water (cold side inlet flow), I never get a convergence. See picture.

Could somebody please give an advice? Now that the simulation (a hudge simulation) works, would be a pity to leave it because of this error.

Thank you