[TRNSYS-users] Mistake in type 33i

[David BRADLEY]

Yose,
   The psychrometrics routine has to use some iterative methods in order 
to solve for all the air properties when it is given certain 
combinations for which the properties cannot be determined directly. 
When RH and w are specified it has to iterate to find a drybulb 
temperature that has the same saturation pressure as the saturation 
pressure that can be computed directly from knowing RH and w. There are 
tolerances on the iterative calculations and with your two input values 
(RH=60% and w=0.006) the iteration continues until the saturation 
pressure for the guessed dry bulb temperature is within 0.01 kPa of the 
saturation pressure computed from RH and w. Tightening the tolerance on 
that iteration (which is one of a few iterations) causes the recomputed 
RH to come out closer to the starting value but I suspect that simply 
tightening the iterative tolerance would not always result in the 
recomputed value being equal to the starting value.
kind regards,
  David


On 11/05/2015 03:55, Yose Wandy wrote:
>
> Hello TRNSYS experts,
>
> There seems to be a mistake in the type 33i, it modified the Inputs 
> that I gave, resulting on wrong value (e.g. dry bulb temperature, 
> enthalpy, etc.)
>
> I attached a small example that shows the difference between the 
> relative humidity input & output, in this case, it shows a difference 
> by 0.09%.
>
> Does it supposed to do that? Anybody have any idea how to fix it or 
> get around it? Any help would be appreciated.
>
> Thanks in advance.
>
> Best regards,
>
> Yose Wandy
>
> --------------------------------------------------------------------------------
>
> Yose Wandy  B.Sc.
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> Wissenschaftlicher Mitarbeiter
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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