The equations in the LMTD link give sensible answers, Thanks.
Although they asume that surface heat transfer cooeficients are constant, so I wouldnt use them where the air flow rate also changes.
Hmm, I have a similar question but this doesnt seem to have been answered definitively.
Heres my version of the problem:
Nearly all manufacturers data on chilled water coils is for 6/12 degrees C water.
I am looking at the impact of using 9/15 chilled water in a datcentre to save energy (More...