Chilled water buffer vessel sizing

[Cooky]

Does anyone have an equation that will calculate the required volume for a chilled water buffer vessel?

I use a 'rule of thumb' of 3 litres of fluid per kW of nett cooling, but I am after an equation that takes other variables into account. Such as number of chiller starts per hour, flow rates, desired temperature fluctuation.......

Thanks for your help.

 

[Shmulik]

I would suggest the following article:

http://www.pmengineer.com/CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,2730,11534,00.html

 

[1969grad]

See ASHRAE handbook for sizing expansion tanks. The tank can have a bladder, use compressed air or be open to the atm.

 

[grim900]

Sorry, very late reply to this and i guess you may not need it now but....

According to York: V=N x 60 x Z / 4.18dt

V= total system water content (Litres)
N= chillers first capacity step (kW)
Z= minimum allowable running time (min 5 mins)
dt= temp difference at minimum partload condition (say 2 deg C.).

This allows the chiller to operate smoothly at low load capacities and should provide sufficient thermal storage to give at least 5 mins operation after the machine has stopped running. This ensures the equipment doesn't keep stopping and starting at low load conditions.....by now, you probably already know all this!!