Re: [TRNSYS-users] dynamic data invalid data points

[Jeremy Osborne <j.osborne@student.unsw.edu.au>]

Thank you all for your input, I found a neat solution that could easily be implemented from a combination of your responses. 

Simply make the invalid (unavailable data points) massive numbers and then use TYPE581 (an interpolater) and an equation to read the same data file and the equation to switch the chiller off using a less then statement if the data is also massive (i set used control = lt(data, 1.22) since the max possible output of valid data was 1.2). 

Not the greatest but much better then an 50 individual equations specifying ranges of the data. 

TYPE107/680 (same component) is programmed incorrectly for another reason not taking into account the actual capacity of machine to work out the required energy input. Therefore used an modified version of type677 combining the data files S1 and S2 into the same reader because the broad chiller capacity is dependent of 3 independent variable TempHW, TempCW, and TempCHWsetpoint. To more accurate adding TempHW, TempCHWsetpoint to the last data file would be best since the required input is also dependent on these. One other fix to type677 was to make the frac of design cap also dependent on the actual capacity of operation not only the designed capacity. 

Kind regards, 

Jeremy Osborne

On Mon, Feb 8, 2010 at 5:22 AM, Jones Marcus <Marcus.Jones@ait.ac.at> wrote:

Could you use an equation instead of changing the fortran code? Something like (CW greater than 24C) AND (HW less than 85) AND (Tset less than 7) THEN (control signal = 0)? Equations are useful for quick fixes if you don’t want to recompile the fortran type.

 

Marcus

 

MARCUS JONES, MSc

Energy Department

Sustainable Building Technologies

 

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-----Original Message-----
From: Jeremy Osborne [mailto:j.osborne@student.unsw.edu.au]
Sent: February 8, 2010 7:08 AM
To: trnsys-users@cae.wisc.edu; techsupport@tess-inc.com
Subject: [TRNSYS-users] dynamic data invalid data points

 

Dear All,

I am modeling a BROAD single effect absorption chiller using type680. This uses the catalog data lookup approach. Not all data points are available for all operation conditions, for example, with cooling water (CW) in of 30C, Set point Temp 7C, and hot water (HW)  input of 85C there is no capacity data point because it is below 50%, however there is a data point available at CW of 24C, set point temp of 7C and HW input of 85C so we need to have the 85C included in the data file.

The problem is what to put as the data point in these invalid points?
 Zero (0) works for most, as it just turns the chiller off, but a problem occurs when the conditions are between an invalid and a valid data point because the dynamic data point interpolates between the 0 and the real value leading to unrealistic data.

There needs to be a way to switch the chiller off when an any invalid data point is used.

One solution is to add another 0, Zero point very close to each side of the point, for example(not exact), do 85, 89.9, 90.....  = capacity 0, 0, 0.74.....

This would minimize the interpolation chance, however not great and pointful to create the data file.

Another solution would be to put NA or something in the data file for the invalid points, and change the fortran code to recognize this and switch the chiller off. Similar to the errorif  function in Excel.
However my fortran is very limited and i couldn't find anything on the web.

Has anyone found a better solution or can help with this?

Kind regards,

Jeremy