Cooling Tower Buffer Tank

[olmedo]

I have seen some installations use an intermediate tank between the cooling tower and the chillers, both the supply and return water passes thru this tank.The reason they do this is to remove air from the water thus preventing it from entering the chillers. IS this a good practice and what is the alternative?

 

[KenRad]

Olmedo,

I can't see much of a difference in air removal between having a separate tank, or the utilizing the tower sump volume for this purpose. I suppose that you could size the tank larger than the sump, to allow more time for air to settle out. But with a properly designed and operated piping system, you shouldn't have air problems on the water side of your condenser barrel anyway.

Are you sure that they are doing this for air removal reasons? Such remote tanks are sometimes used in cold climates to prevent freezing of the condenser water; the tank is placed inside the building, and when the system is shutdown, all of the condenser water drains from the tower (at a higher elevation) to the indoor tank. This eliminates the need for external sump heat for freeze protection.

---KenRad

 

[ChasBean1]

The buffer tank is to add system volume to enable smoother control transitions. Small volume systems can experience jerky control trasitions with modulation of control valves, etc. (if "jerky" can be considered an acceptable engineering term). I don't know why both the supply and return go through the tank - hopefully they are kept separate.

 

[lilliput1]

You should separate the CT return water (at 95°F max design) from the CT supply water (at 85°F max design) or you will not get the design performace out of both the chillers & cooling towers. To remove air from the condenser water piping, put valved automatic air vents at the high point of the piping downstream of the condenser water pump. Do not put upstream of the pump since this can be below athmospheric pressure and will draw air in instead of out. Put the discharge of the automatic vent to the nearest floor drain. The valve is to allow servicing of the vent with the valve closed.
Provide adequately sized equalizer piping between cooling tower cells & mount the cells at the same elevation. Provide service shut-off valve at the equalizer connection.

 

[olmedo]

Thank guys, the buffer tank is provided with two compartments, one for cold and the other for hot. The design is such that the water overflow to the other compartment at increased flow conditions.

 

[niwrep]

Supply and return valve should not pass together in same tank. If this happens, supply and return water temperature will equalize and it will be suplied to chiller which is not efficient. Having buffer tank is a good idea especially treating condenser water.
thanks,
erwinpetiluna