Water-to-Water Direct Contact H.Ex. Tank

[NNNNNN]

Dear All,
Need your help with the calculation and tank shape/with its partitions and any information you think I need to do so.
we do have cooling water chiller, it has its first loop (primarily loop - fresh water) to out of it water 84 gpm comes out of it with a temperature of 45 deg F and designed to have water get back to it with temperature of 54 deg F. this recirculate with an outside small SS tank, that from this tank a secondary loop starts has its own pump)
Secondary water cooling loop takes the water from this tank via pump 125 gpm to be no less than temperature of 68 deg F (20 deg C) pumped to cool system in a closed loop that has a pressure drop of 6 bar pressure drop). the water to get back to the mentioned above tank with temperature around 86 deg F. and so on continue all day.
Looking to have the tank mentioned above as heat exchanger direct water to water (not shell and tube or plate Heat Exchanger). Please if you can help how to do that with a small as possible tank. sure this tank need some internal partition to keep the water temperatures as mentioned above to each of the primarily cycle and the secondary which each has its own pump.

Thanks.

[frank]

It sounds like you are describing what we call a "low loss header"
If you do an internet search you should find lots of sizing information

[NNNNNN]

Thank you Frank,
But with the Low Loss Header, we will not be able to satisfy the temperatures In and out as I mentioned in my threat? Chiller loop/primarily 45 deg F and back 54 deg. F and the secondary loop 68 deg F and back 86 deg. F?
Thanks.

[NNNNNN]

Thank you Frank,
But with the Low Loss Header, we will not be able to satisfy the temperatures In and out as I mentioned in my threat? Chiller loop/primarily 45 deg F and back 54 deg. F and the secondary loop 68 deg F and back 86 deg. F?
Thanks.

[Brian_UK]

If the fluid is inside the same vessel being mixed together you have a near impossible task of maintaining four distinct temperatures. Simple physics overcomes design wishes.

[NNNNNN]

If the fluid is inside the same vessel being mixed together you have a near impossible task of maintaining four distinct temperatures. Simple physics overcomes design wishes.

Then what would be the solution in you opinion for that? I am thinking to have proportional three way valve in the secondary loop just before the water get back to the Low Loss Header or can be named as I have today seen in some, called Hydraulic Separator that returns the water to upstream the secondary loop pump. What is your opinion with that three way valve that in order to have right temperature of water going to cool the system?