[superluserdo]

>Factor in pipe losses on the return leg and you're back at the data centre with maybe 35°C inlet rather than 45°C

Surely having the input fluid being colder is a benefit, not a problem? Just run the fluid more slowly through the system?

[matt-p]

In essence you can't really because slower flow rate makes the heat transfer less efficient. You'd be halfing the flow rate in that example.