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Re: [TRNSYS-users] (no subject)

Weihua,

 First, if you are using Trnsys18 then I would recommend that you work your way through some of the tutorials that are in the 09-Tutorials.pdf (..\Trnsys18\Documentation). There are a lot of issues in your email that are very fundamental to the correct use of Trnsys and that would be worth understanding well.

 The warnings that you refer to are probably warnings about timesteps when the simulated system did not converge. TRNSYS has a limit so that if more than a certain number of warnings are generated, the simulation will terminate with an error. You can adjust the allowable number of warnings before the error but I would not recommend you do so; non convergence issues should be corrected.

 It is hard to tell you how to solve convergence problems; it depends on what you're simulating. The usual problems are that you do not have any enough thermal mass in the loops of a system. For instance if you have a Type1 solar collector, pump and heat exchanger model in a loop then those are all quasi steady state models and there is no thermal mass. The models will react unrealistically fast to external changes and may result in convergence problems. The other typical problem is too long a time step. Trnsys can only make one control decision per time step. If you are controlling a system with a 1 hour time step then the system will likely be unstable and have problems converging. I recommend using something between a 1 and 5 minute timestep.

 For your question about the active layer I would recommend that you refer to the Type56 manual to understand the limitations on the model.

kind regards,

 David

 


On 08/08/2018 19:48, 吕伟华 via TRNSYS-users wrote:
hello,I am student, I use TRNSYS to do some simulation works. I have some confusion during my work. I conducted a simulation system of a new air conditioning system on the pletform of TRNSYS. the type56 was used to build the building model and the active layer was used to simulate the pipe-embedded wall.
My questions are:
1) I have built the simualtion model and it can run successfully. but when I change the weather data from one city to another city, and change the envelope insulation(U value), other things keep the same. then I ran the simulation again, it began to work, but after a period running, it breaked and the message shows that"the maximum number of warnings allowed per simulation has been exceeded". I donnot know why. Can you explain this situation for me? and how should i do ? 
2) similarly, in some simulation, when I set the timestep one hour, it can run successfully, but if I set the time step 30 minutes, or less time, it began to run but then occur the same error as "the maximum number of warnings allowed per simulation has been exceeded". can you help me with this question?
3) for the parameter of the active layer,when I change the pipe wall conductivity value,the allowed minimum water flow will change. the default value is 0.792kJ/hmk，if i change this value to 1.56 kJ/hmk, the allowed minimum water flow willincrease, bigger than 13 kg/h.m2. what is the relation between the pipe wall conductivity and the water flow rate? can you help me with this phenomenon? 
  looking forword for your reply. many thanks!
Best wishes!
Weihua



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David BRADLEY
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