The water in a rack, closed loop, it gets recirculated.
However, the closed loop will run through a liquid to liquid heat exchanger, and that second loop is usually going to a tower to get evaporated.
The plumbing in the rack can be very picky about water quality and want additives that would be very bad in an open loop scenario.
So you end up with people at the rack level talking about ‘closed loop’, but they run through a CDU that is open loop. Basically closed loop when picky about the water, moving heat to open loop where they can actually get rid of the heat effectively.
Closed loop is often relative.
The water in a rack, closed loop, it gets recirculated.
However, the closed loop will run through a liquid to liquid heat exchanger, and that second loop is usually going to a tower to get evaporated.
The plumbing in the rack can be very picky about water quality and want additives that would be very bad in an open loop scenario.
So you end up with people at the rack level talking about ‘closed loop’, but they run through a CDU that is open loop. Basically closed loop when picky about the water, moving heat to open loop where they can actually get rid of the heat effectively.