Multiple cooling towers - Cooling tower staging

[remp]

I am looking at a chiller installation that has 6 no. 2500kW chillers and 6 no. cooling tolwers. The condenser water is piped in parallel for the chillers and a common pipe goes to multiple cooling towers also piped in parallel. The way the BMS is set up, for every chiller that is operating the automatic isolation valves on a corresponding cooling tower open, so in effect each chiller has its own tower to handle the load. At the moment when only one chiller is running we need to run the fans on its tower, it would be better off running the water into the next tower to avoid having to use the fan, I think??
Would I be better off energy wise if all the water is left run through all the towers no matter how many chillers are ON.
If i have only a percentage of the design Condenser water running through a tower will my dirft losses increase greatly?

 

[SAK9]

You are trying to run an induced/forced daft cooling tower as a natural draft cooling tower.I have tried this in the past and it has not really worked for me.If it works,it is good and there will be no drift loss as the fan is not working.My conclusion was that the fill area was not enough to produce sufficient evaporation to bring down water temperature.Could be different in your case depending on your water teperature and wet bulb depression

 

[ChasBean1]

Remp, there are analyses for this if you want to spend the time researching…

From a common sense perspective: using multiple towers increases the heat transfer surface area but reduces the heat transfer at each cooling tower. Lower flow means thicker laminar boundary layers and less heat transfer per unit surface area.

At the same time, moving water through all towers will use less (sometimes zero) cooling tower fan power while changing out water in each tower (see ASHRAE 12), preventing stagnation leading to biological growth/legionella.

Without doing all the homework (sorry) I’d leave all tower isolation valves open at all times unless isolated for maintenance. With all fans off, if CWS temperature still becomes too low, cycle open the tower bypass. As CWS temperature increases, start and run all fans at minimum speed, through full speed as temperature increases.

 

[sridhar1312]

We feel having on/off motorized valve in the outlet of the condenser&chiller to stop low whenever the respective chiller is not in operation.

And cooling tower can be programmed based on leaving temperature of cooling tower i.e cooling water inlet. Based on the cooling water inlet sensed from the header in outlet of cooling tower with so that apprpoiete cooling tower sahll operate. The above may ensure to operate without fan if you are operating only one chiller out of 6 and logic can be incorporated for the fan to come on when the sumtemperature increase.
The above will have redundancy and reliability with energy saving.