Energy Savings

Evaporative Pre-Cooling for Air-Cooled Chillers

Evaporative pre-cooling using micro droplets is a proven and affordable method of enhancing the efficiency of air-cooled refrigeration and air-conditioning plants.
Air-conditioning in the ME can account for 60% - 80% of a building’s monthly power consumption. By artificially lowering the ambient temperature outside, immediate energy savings can be achieved. During this time of escalating energy costs, investing in energy saving technology is a necessary alternative.

How DryMist™ Pre-Cooling Works

Evaporation is the process through which water changes from a liquid to a vapour. For this to take place the bond that holds the water molecules together must be broken. This occurs when the water molecule absorbs a sufficient amount of heat. When the heat is absorbed from an air stream the temperature of the air falls. Evaporative Pre-Cooling with DryMist™ should not be confused with the practice of sprinkling water on an undersized condenser on a hot summer’s day. This is mostly done to increase cooling capacity. DryMist™ pre-cooling prevents these unwanted consequences.

The evaporative cooling process begins as water is passed through a pre-treatment that de-calcifies the water, followed by a micro filtration system. The filtered water then flows through a direct displacement high-pressure pump which increases pressure to 70-90 BAR. Maintaining a suitable high pressure is of utmost importance to achieve micro droplets small enough to flash evaporate.

An environment friendly additive is dosed into the supply water which breaks the surface tension of the water. This enhances evaporation by an additional 30%. Finally, the clean, pressurized water travels through high-pressure tubing to DryMist™ nozzles strategically placed around the system to be cooled.

A properly designed DryMist™ system will cause instant evaporation of the micro droplets into the air stream. The mixture of water and air reaching the condenser coil will be in a gas phase and at a considerably lower temperature. This will increase heat transfer and cooling capacity which results in decreased energy consumption. To achieve the best possible results many factors should be taken into consideration. Some factors to consider are nozzle design, size and placement, optimum water quality and pressure, system control and safety features.

Measuring the Energy Savings

Through extensive research and a lengthy consultation process with local air-conditioning engineers experienced in local climatic conditions, Green Sense developed an integrated spread sheet that calculates potential savings that may be achieved. There are multiple variable inputs which include cost of power, cost of water, current kW draw and size of the units. The spreadsheet goes a long way in determining the potential energy savings and provides a good basis to work from. The spreadsheet greatly facilitates communication with decision makers as it contains all the key factors in order to make an informed decision.

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