Delta T Calculation

[jasper]

Normally the controller would notice that the unit of measure is not the desired one. However, particularly in the case of the missing delta flag it chooses to be silent about that, as this flag is not (yet) widely supported. If I would flag this particular situation as 'wrong' I am afraid that some scenarios will not work, such as using a delta-temperature of a third party heat exchanger unit operation that appears to have the unit of measure of temperature.