Re: [TRNSYS-users] Solved issue with "MoistAirProperties"

[David BRADLEY <d.bradley@tess-inc.com>]

Antoine,

  Thanks for sharing your solution. I would be quite grateful if you would be willing to share the code. We have run into a fixed a lot of these kinds or errors. Many times the iteration will solve to within the original (tighter) tolerances if the initial guess values are reset but some of those routines leave the last guess values behind and so they are used as a starting point for the beginning of the next iteration. Unfortunately our solution does not work in every case so we implement fixes as we find problems.

kind regards,

 David

On 10/09/2019 02:56, LECONTE Antoine 219492 via TRNSYS-users wrote:

Hello,

 

Here is my recent experience that I think can be useful for some of you.

 

Problem : When simulating the operation of an Air to Water Heat pump (Type 941 from TESS lib), the simulation starts normally and then freezes few hours later without letting any message (no warnings, nothing in the log or lst file). Whereas the HP operation conditions are quite usual and there is no sudden events at the problematic simulation time.

 

Reason : Actually, Type941 calls the TRNSYS “Moist Air properties” functions to have the states of air at different points of the HP. The air can be close to the saturation pressure. When close to those nonlinear conditions, the implemented solver in this function (secant method) can turn around the solution without reaching the required tolerance (being still very close). In this case, the calculations can’t go out of this iterative solver. The simulation is stuck.

 

Possible solution : I have modified the code of the “Moist Air properties” to gradually raise the tolerance when there is too much iteration in this kind of solver. So that a solution can be found at each time and avoiding such a problem. I can share my modified code if needed.

 

 

Best regards,

 

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Antoine LECONTE Research Engineer National Institute of Solar Energy  CEA/LITEN - Department of Solar Energy Building and Thermal Systems Commissariat à l’énergie atomique et aux énergies alternatives Bât. HELIOS, 50 avenue du Lac Léman | F-73375 Le Bourget-du-Lac T. +33 (0)4 79 79 21 38 | F. +33 (0) 4 79 62 13 74 | antoine.leconte@cea.fr; www.ines-solaire.org; liten.cea.fr

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