hello every body

I'm working on designing pipes net for chilled water that will be used in a food industry

I plan to use a tank for saving the chiled water and to keep the water in a stable temperatue

but as you know the chilled water will be re-mixed with the compensation water which 

 gains   a high temperature so I choosed to use a partition to seperate the chilled water from

the compensation water .

so if any one has an idea about designing such a tank and how to control the two mounts

of water and if in the case I don't use the chilled water what is the best to design ( let the

water go back to the tank by two way valve or let it go back to the tank by it self )

any references or books could help me in this field ?

thanks ly for your help