The subject matter described herein relates to heat exchangers and, more particularly, to a bi-phase heat exchanger for cooling air flowing through an equipment rack.
Data centers are typically cooled by perimeter cooling. Air to liquid heat exchangers are situated around the outside of the data center and air is pumped from the interior of the data center through the air to liquid heat exchangers. The air travels underneath the floor of the data center and then upwards through air vents in the flooring into aisles positioned between rows of equipment racks. The cool air in the aisles passes by convection between equipment positioned within the racks. Warm air is discharged on the opposite side of the row of racks into a warm aisle. The warm air in the warm aisle passes by convection to the air above the equipment racks. The warm air travels along a ceiling of the data center and downwards to the air to liquid heat exchangers. The air cycle is continuous to keep a temperature of the center at a predetermined level for efficient operation of the equipment.
As an operational capacity of the equipment increases, an increased amount of cooling is required in the data center. The cooling capacity of the perimeter cooling may be limited. Accordingly, air to water heat exchangers may be attached to the equipment racks. In particular, the air to water heat exchangers may be attached to the equipment rack at a location where the air flow exits from the rack. Such heat exchangers are generally referred to as rear door heat exchangers. A rear door heat exchanger uses water as a cooling medium because water has a relatively high specific heat in comparison to other coolants. The water supplied to the rear door heat exchangers is typically at normal room temperature or only slightly lower. In particular the temperature of the water may be within a range of 18° C. to 22° C. The temperature of the air exiting the equipment is generally in a higher range, for example, 35° C. to 45° C.
However, conventional rear door heat exchangers using water as a cooling medium are not always accepted by customers, due to policy decisions or just aversion to any risk of water in their environment. Using another medium such as refrigerant provides an alternative offering where water based systems can't be deployed. However, a specific heat capacity of conventional cooling mediums is generally lower than a specific heat capacity of water. Accordingly, conventional cooling mediums may not be capable of absorbing as much heat as water is capable of absorbing.
A need remains for a heat exchanger that operates with a coolant other than water while maintaining a sufficient cooling capacity.