We have built a prototype system that uses 1/4 of a rack heat exchanger. A stack of 2 heat exchangers. One connected with an outside “pre cooler” unit, the other connected to a chilled water source.
By supplying water from the pre cooler we are able to reduce the amount of water required from the chiller to cool the air coming from the rack. The colder the outside air temperature the less chilled water is needed. The system can switch between 100% pre cooler, 100% chiller or a mixed mode.
“Outdoor” Pre Cooler brings water temperature to within 1-2 degrees of ambient.
Rear Door Heat exchanger, provides direct cooling of the air as it exits the rack. Two heat exchangers are combined to work as 100% pre-free cooler, 100% chiller or a mixed mode. A series of valves controls the mixing of the water.