[TRNSYS-users] Time dependency

[Kim Goethals]

Dear TRNSYS-users,


I am performing a simulation of a typical office room which is cooled by 
night ventilation. To study the influence of convective heat transfer I 
implement convective heat transfer correlations. Since I got a 
convergence error doing so, I recall the needed parameter values from 
the previous time step to calculate the convective heat transfer 
coefficient. To get a time-independent solution I decreased the time 
step gradually. However, when I use a time step of 0.5 or 1s the results 
deviate seriously. Therefore, I have completely stripped my model to 
eliminate the influence of controls of installations, schedules etc. 
Moreover, I have used constant convective heat transfer coefficients. A 
graph of the indoor temperature shows that the simulation with a time 
step of 0.5s doesn’t start from the initial value while the simulation 
with 1s approaches the temperature profile of 0.5s. Does anyone have an 
explanation?


Best regards,

Kim

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