Chilled Water and Condenser Water Piping

The 7.5 ft/s seems reasonable for first estimation. For a project of this size, you might want to do an economic analysis. Select a few pipe sizes either side of this initial choice, calculate the pressure losses via Darcy-Weisbach, Williams-Hazen, or other accepted formula (or by whatever formula your local jurisdiction may require). Then size the pump(s) accordingly. Compare the installation costs with the operating costs over the desired time frame. Don't forget pipe insulation for any chilled water lines. You will almost surely find that much larger or smaller piping is uneconomical, but two or three standard pipe sizes in the middle will be credible options.

For a liquid, just keep the velocity between 1m/s and 3m/s, as a rule-of-thumb. If it's outside those limits, the pipe diameter is wrong.

Hi m z,

The real issue with district cooling or heating is the management of the differential temperature. If you can double the delta T then you can halve the Q!

I've spent years sorting out systems where the Q is far too high and the pumping losses are excessive. You should look very closely at the application end and see how to maximise the uptake of the thermal energy by stretching the deltaT. I know that large scale chilled water distribution is difficult to control and pumping costs become very uneconomic without demand side regulation. If you are using waste heat as the source of the cooling effect think in terms of distributing the hot water(larger Delta T) to absorbtion cycle chillers and save on the pumping costs.