Air cooled systems use dry cooling. Air passes over a finned heat exchanger containing the process fluid. Heat is sensibly transferred from the process fluid in the heat exchanger to the airstream flowing through the unit. To efficiently cool the process fluid to the desired temperature for the system, the dry bulb temperature must be significantly lower than the fluid temperature. In hot climates and during periods of high ambient temperatures, this technology results in higher process fluid design temperatures and lower overall system efficiencies. 

Air cooled units consume a great deal of energy to operate the fans, which must move a large volume of air. Significantly more heat transfer surface area than the other cooling methods is also required, typically resulting in a much larger footprint for dry coolers than systems that utilize either evaporative or adiabatic heat rejection. The higher system design operating temperature results in significantly greater energy consumption for the system. 

Water cooled systems typically use evaporative heat rejection to maximize energy efficiency and minimize footprint of an installation. Evaporative cooling efficiently transfers heat from the recirculating water and discharges warm, moist air to the atmosphere by utilizing both the sensible and latent potential of the air. Evaporative heat transfer significantly reduces the required fan power, footprint, and, most importantly, the overall system energy consumption. This energy consumption is significantly less than the total energy usage of similarly sized systems utilizing either air cooled or adiabatic solutions. In cooling towers, fluid coolers, and evaporative condensers, a distribution system passes water over a heat exchanger such as fill media, coil or other heat exchanger. Using the same physics as perspiration, the evaporative process cools the surface of the water as the H2O molecules transition from the liquid to the gas phase. Heat is then transferred to the airstream and ultimately into the atmosphere through the evaporative cooling process. 

The evaporative process is dependent on the ability of the entering air to absorb the evaporated water molecules using the enthalpy driving force of the air. The drier and less humid the air, the higher this potential, as indicated by the wet bulb temperature, which is always equal to or less than the dry bulb temperature of the air. The wet bulb temperature is related to the amount of moisture in the air relative to the dry bulb temperature. An evaporative product can lower the process fluid in the heat exchanger to within a few degrees of the wet bulb temperature. Evaporative products have proven to be powerful, energy-efficient cooling solutions in all climates.Evaporative products use the power of water to save significant amounts of energy. To optimize the water used, design considerations evaluating water quality, upgrading the materials of construction of the units and implementing an effective water treatment program. 

Adiabatic cooling products also uses evaporation, but as a means of cooling the entering air passing through a finned heat exchanger. In a properly designed and operated system, the finned heat exchanger stays dry, protecting the surfaces from scale and corrosion. The air can be cooled by either spraying water into the airstream or by using wetted pads that provide a surface for water and air to interface. In the first case, the goal is that the water sprayed into the airstream evaporates before reaching the finned coil, avoiding scaling and corrosion on the coil which can negatively impact system efficiency and equipment lifetime. In the second case, a wetted pad is used to cool the entering airstream. The pads are specially designed to retain water on the surface of the pads to ensure that it does not carry over to the finned coil minimizing the potential for scale and corrosion. The water distribution system maximizes pad efficiency by effectively wetting the pad to minimize process fluid temperatures and prevent scale formation.

Hybrid products use a combination of dry and evaporative cooling technology. Combining the benefits of both, hybrid products can be ideal for water-sensitive applications while still offering high energy efficiency.