[TRNSYS-users] TIME

[Jeff Thornton]

<I am creating a model using differential equations. I use the DTDT()=
function Method so as to solve them Numerically. My model is suposed to be
only SI units and that for i'd love the Transys solver to solve them in
seconds. The problem is that TRANSYS is automatically converting the the
TIME to hr and thus my simulation is wrong. My question is how can I tell
TRANSYS to use seconds as the calculation unit. >

It's a pretty simple conversion from hours to seconds so I'm somewhat
confused with your tech support question.  TRNSYS keeps track of time in
hours - always has and likely will for quite a while.  You won't be able
to change that.  So if your model operates in true SI then you'll have to
do the conversions from hours to seconds (and back again if needed) inside
of your type.

For example if we have the governing equation:

C DT/dt = Qdot

where C is in units of J/K and Qdot is in Watts (Joules/seconds) then we
simply define DT/dt using hours

DT/dt=Qdot/C*3600 (seconds/hour)

This approach will then solve for T correctly using the TRNSYS equation
solver.

Jeff


Jeff Thornton
President - TESS, LLC

2916 Marketplace Drive - Suite 104
Madison WI 53719 USA

Phone: 608-274-2577
Fax: 608-278-1475
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