Start with the fact that it takes 1 BTU to heat 1 pound of water 1 degree F. It works backwards, too.
Do you know the range of needed flow rates of chilled water? I assume you want to produce chilled water at times of low demand and use it during times of high demand. If not, then why store chilled water? It just gets warmer with time.
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We have met the enemy and he is us . . . Walt Kelly
What is your heat load and what is it's cycle rate. i.e. BTU's / min. Also what is your chiller capacity.
Your storage vessel has to be large enought to provide sufficient chilled water for your process. It will help to provide insulation on the tank.
If the temperature of the water is critcal (chemical process) consider a mixing valve to blend return water and supply water. you will need two water pumps one for the process, one sized to provide the correct process flow and one chiller pump sized for the chillers evaporator flow)
A major reason for a buffer tank is to provide for stable control of the chiller or boiler. Normally a heating or cooling system has at least 10 minutes of chilled water or hot water in the loop. That is it takes a packet of water 10 minutes to make a circuit through the system. If there is too little mass of water in the loop, it becomes very difficult to control the chiller/boiler. For this type of problem, figure out the volume of water in the loop and heat exchangers, look at the water flow rate and get a big enough tank to get a volume that would take about 10 minutes to complete one circuit.
be specific as to the type of application, volumes, temperatures, etc... then I should be in a position to assist in the conceptual design and give you guidelines on detailing your engineering.
Ciao
Sizing
