Lets calculate the Log mean Temperature difference on a heat exchanger.
The calculation is this
LMTD = ((Temp Hot Inlet - Temp Outlet Cold) - (Temp Outlet Hot - Temp Inlet Cold)) / LN ((Temp Hot Inlet - Temp Outlet Cold) - (Temp Outlet Hot - Temp Inlet Cold))
#Previously when building calculations you would build them external from the system that the calculation is going to run in.
NOTE - We are going to build this calculation using the Chart macro that is accessible in the Basket by selecting Trend. The method is exactly the same for building it in a KPI
Step 1
- First step is to go to the search macro or a page that contains the relevant tags.
- Right clicking or drag them into the basket.
- Remember you have the option saving the basket.
- Once you have added the tags you need in this calculation. We are ready to get started.
Step 2
Two ways of building a multiple layer calculation.
Build the calculation in layers adding each layer into the basket.
DIV(SUB(SUB(0,0),SUB(0,0)),LN(SUB(SUB(0,0),SUB(0,0))))
Then drag from the basket the relevant tags into the calc builder