[TRNSYS-users] Type 60d Error

[Michaël Kummert]

Sigrid,

> I have modeled a simple combisystem with a type 60d including two submersed heat exchangers, 1 inlet and 1 outlet.
> I can not run the simulation a whole year, I get the following error:
> %%% TYPE60 WARNING:  UAhx UNABLE TO
>  CONVERGE IN 500 ITERATIONS AT TIME=
>    18.00000             500 %%%
>    18.00000    B   1569.571    
> Nevertheless if I run the simulation for each month there is no problem. 

This is a known issue in Type 60, which has been addressed in TRNSYS 16.
Usually it is possible to alleviate the problems by reducing the time 
step. The problem is also often linked to using glycoled water in the 
heat exchanger. It is possible to use pure water and "cheat on the 
flowrate" to obtain the same capacitance flowrate.

The fact that you can run the simulation one month at a time probably 
comes from the "warnings" limit. You can increase it in your input file 
and then you should be able to run the file for a whole year. You should 
be especially careful and check that the results make sense, though. 
Sometimes the non-convergences in the heat excahgner happen at very low 
flowrate so they don't have a real effect on the simulated performance 
but in some circumstances such problems can lead to important errors in 
the heat exchanger energy balance.

So my recommendataions are: try to reduce the time step, calculate and 
check the heat exhanger energy balance in your simulation and increase 
the maximum number of warnings. Also possibly use pure water with a 
modified flowrate if you were using glycol.
Or give a try to TRNSYS 16!

Kind regards,

Michaël Kummert

-- 
_________________________________________________________

Michaël Kummert

Solar Energy Laboratory - University of Wisconsin-Madison
1303 Engr Res Bldg, 1500 Engineering Drive
Madison, WI 53706

Tel: +1 (608) 263-1589
Fax: +1 (608) 262-8464
E-mail: kummert at engr.wisc.edu

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