Hi everyone! I have read previous mails about problems with convergence in closed loops but I can't solve my problem...I have tried with diferents options: rearranging components in control cards (in logic order), decreasing time step, putting types with higher thermal mass at the end of the order of calculation. Just one option I haven't tried: putting type 31 instead of just links between types.
But one option worked and helped with convergence: putting type 661 (delayed output device). The problem about this is that results are not correct.
About my simulation: I'm working on a hybrid heating system for a house. It consists in a heat pump that gives heat to the house through radiant floor, and extracts heat through horizontal ground heat exchanger and flat plate solar collectors. This system has two tempering valves:
1. First valve controls that mass flow does not pass through horizontal ground heat exchanger if soil is very cold (mass flow goes through a bypass)
2. Second valve controls that mass flow does not pass through tank if tank outlet towards the load is colder than mass flow.
The diagram is attached to this mail.
I ran the simulation and I obtained results so weird: sometimes the thermostat gives the signal of 1 (on, when the house need heating) and the flow out (to source) of heat pump is 0. And sometimes thermostast gives the signal 0 (off, house doesn't need heating) and the flow out (to source) of heat pump is 1532 kg/hr or 3065,83 kg/hr. Mass flow of heat pump to load is ok, but to source is strange. Then I realized that all mass flows of the side of the source were weird in the system: diverters, pumps, ICG, tank...The side of load is ok.
I think that some type is giving outputs in a different time compared to other types, but I don't know what type is giving the problem: when I see the list file, it says:
*** Warning at time : 2935.000000
Generated by Unit : Not applicable or not available
Generated by Type : Not applicable or not available
TRNSYS Message 441 : The inputs to the listed units have not converged at this timestep. The values at the last iteration will be used and the simulation will proceed.
Reported information : UNITS: 21 23 42 46 45 38 40 22
*** Warning at time : 3000.000000
Generated by Unit : 27
Generated by Type : 2
Message : The controller was stuck during 12 percent of the simulation timesteps.
*** Warning at time : 3000.000000
Generated by Unit : Not applicable or not available
Generated by Type : Not applicable or not available
Message : The simulation failed to converge during 2 timesteps (2% of the time).
*** Warning at time : 3000.000000
Generated by Unit : 23
Generated by Type : 114
Message : Pump mass balance failed during 7 timesteps. Please check the connections.
So I don't know which type is giving the problem (messages indicate problem with heat pump, pump, tees, tempering valves and tank) , and I don't know if type 661 can help in this situation. Somebody can help me please or give me some idea of what is happening? I can't detect the problem since two weeks!
Thank you in advance! And sorry about this too large text!
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Alejandra Vargas Cáceres
Estudiante Ingeniería Civil Mecánica