[TRNSYS-users] dynamic data invalid data points

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

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