[TRNSYS-users] Problem with type60

[David Bradley]

Matteo,
 You need to use a smaller timestep; something on the order of 5 to 15 
minutes would be appropriate. I'm actually somewhat surprised that the 
simulation runs at all - the data file has hourly values in it and with 
a two hour timestep, it would have to skip every other point in the data 
file. I didn't think Type15 could do that. I would also recommend that 
you put some pipes between the tank and solar collector. You need to 
make sure that the total volume of liquid that the pump can transfer in 
the space of one timestep is smaller than the volume of the loop itself. 
The pump and solar collector models neglect the volume of liquid that 
they contain. I believe that the Type60 internal heat exchanger 
calculates the liquid volume. However that volume may be smaller than 
the pumps rated flow rate times the timestep which, from a simulation 
point of view, means that the liquid would make more than one complete 
circuit within the space of one timestep. That can cause numerical 
instability in your simulation.
Kind regards,
 David


Matteo DF wrote:
> Hi,
> I'm trying to simulate a small project with a solar collector, a pump 
> and a storage tank. I used 12 m^2 of panels which flow goes directly 
> to the heat exchanger of the tank... The circulation pump provides the 
> correct flow.
> I have some difficulties as I get some convergence warnings (warning 
> 441) The convergence error is between the solar unit and the tank one.
>
> I attach my little project. Can you tell me were I'm going wrong?
>
> Many Thanks.
> Matteo.
>
> -- 
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> pensare ciò che nessuno ha mai pensato.
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