Operation and Installations
Chillers using water cooling are typically intended for indoor installation and operation, and are cooled by a separate condenser water loop and connected to outdoor cooling towers to expel heat to the atmosphere. Chillers using air cooling are manufactured from copper tubes for refrigerant flow, and aluminum fins for the air flow. Chillers utilizing air cooling are intended for outdoor installation and operation. Air-cooled machines are directly cooled by ambient air being mechanically circulated directly through the machine’s condenser coil to expel heat to the atmosphere. Now that we have discussed the differences in water cooling and air cooled condensers, we can move on to discussing the pros and cons of these machines, and what may be better than the other.
Cost and Effectiveness
The initial cost of chillers with air cooling is generally lower than water cooling based chillers, as air systems do not require cooling towers, condenser water pumps and associated HVAC components. Small systems are almost always air cooled since the extra requirements of water treatment and maintenance are capital intensive and will not be offset quickly by the lower operating costs. Waiter cooled chillers may be a better choice for some applications because of better heat transfer properties of water as compared to air cooled chillers. The primary advantage of water is that the film coefficient is 10-100 times better with water than air. Film coefficient controls heat transfer with given constant area and temperature difference.
Not only are larger chillers generally more expensive, but in comparison to size, air cooling chillers are usually less expensive than water cooling chillers. Even experts in the HVAC field of work have no exact answer when it comes to “are water cooled chillers better than air cooled chillers?”. Another issue to take into perspective is if you are in an area where water and cost of water is not an issue, which is a large point to consider when deciding on a system to use. If space is a problem, air cooled chillers can take great utilization in open spaces such as parking lots and roof or ground areas, where as water cooled chillers take up much more space and need a closed circuit along with a water tower to hold the cooled water.
The fact is that it all depends, water cooled chillers will normally condense at an average lower pressure than air-cooled chillers. This is because the water temperature will usually be less than the air temperature. If your condenser is operating at lower pressure then it is directly reflected and translated into lower operating costs.