[TRNSYS-users] whole number of simulation start time

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Dear Trnsys user,

When I start a simulation and I do not set the simulation start time to a whole number (not hour 1 but hour 1.1 for example) I get very strange simulation results.
Attached I did a basic simulation where you can see the problem by comparing the simulation results with a start time of 0 hour and a start time of 0.1 hour for example.

Does anyone know if it is always necessary to set the simulation start hour to a whole number?

Thank you for your help,
Simon Binnemans

Simon Binnemans's picture
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Joined: 2016-04-05
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Simon,
You can start a simulation at non whole numbers but in this case you
have to be very careful about the difference in output devices between
"relative time" and "absolute time" Many printing and integrating
devices give you a choice. If you choose relative time and integrate
hourly, you will get results that are in one hour intervals starting at
whatever simulation start time you choose: time = 1.1, 2.1, 3.1, 4.1,
... If, on the other hand, you choose absolute time and integrate hourly
then the first integration period won't be a full hour. Your intervals
will be time = 1.1, 2, 3, 4, ...

And of course your simulation start time must be an integer multiple of
your timestep. You cannot, for example, have a timestep of 1 hour and a
start time of 1.1.

Regards,
David

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David BRADLEY
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Thermal Energy Systems Specialists, LLC
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Joined: 2011-10-02
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