Using the evaporation of water to provide cooling has been with us since ancient times. Beating the summer heat in places like Mesopotamia and Nile certainly had its adherents in the upper class. In ancient Egypt and Persia breezes blew from predominate directions. These were captured and sent through a chamber where there was water. As the water absorbs the heat from the air and evaporated, the air was cooled the breezes circulated it through the palaces.
Water Has a High Heat of Vaporization
Evaporative cooling runs from the use of misters to cool patios and porches, single room units to systems for the whole house. The fine water mist absorbs heat on evaporation and cools the air. Any breeze blowing through helps to circulate the air. Water has what is called a “high heat of evaporation”, meaning water absorbs relatively high amount of heat before evaporating. In farming communities that experience high heat, a noticeable drop in temperature is experienced as you pass by fields under irrigation. This is due to the evaporation of water. Plants, particularly trees as they transpire produce a cooling effect from the evaporation of water off the leaves. Trees not only provide shade but are nature’s evaporative cooling apparatus.
Evaporative Cooling System Design & Working Principal
In home evaporative systems the ‘swamp cooler’ draws air from the outside. Fiber pads hold water that is pumped to them. As the warm air is drawn through the pads it picks up water that evaporates cooling the air. The air is then ducted into the house. Evaporative coolers work good in high temperature, low humidity conditions. The lower the humidity the better, at a 100 °F (38 °C) and a relative humidity of 5% a drop in temperature to 71 °F (21.6 °C) can be expected. But at 50% humidity the drop will be only 12 °F (7 °C) to 88 degrees Fahrenheit (31 °C).
Evaporative Cooling Efficiency
Having only to run a relatively low amperage fan motor vs. compressors and fans, the evaporative cooler is very economical in comparison to the typical air conditioning or heat pump system. Misters can be adapted as a pre-cooler for your A/C and pre-cool air flowing through the condenser improving the efficiency of the air conditioner and lowering power consumption and are available in kit form. Commercial A/C equipment use pre-coolers as well.
Evaporative cooling works on high bulk airflow. In the US the unit used to measure airflow is CFM or cubic feet per minute. A 1500 square foot home with 8 foot ceiling needs to circulate 6,000 CFM for effective cooling. Many have ducts in the ceilings to promote circulation through the addict, cooling the addict as well, or simply crack open a window a bit.
Evaporative Cooler Installation, Emergency Repair, Preventative Maintenance & More in Greater El Paso, Texas
Some installations piggyback both A/C and evaporative systems to provide cooling in high humidity conditions.
With evaporative coolers the temperature will drop but interior humidity will rise. A two stage evaporative cooler recirculates the interior air through a heat exchanger serviced by the evaporative stage of the cooler. This allow for cool, but drier air in the interior of the home. A water pump and blower in the ‘wet stage’ operates the evaporative cycle, while the dry stage circulates interior air. The stages interact through the heat exchanger.
Economic cooling is the prime advantage of an evaporative cooler in low humid areas, and a possible consideration for new construction. Portable units are available to provide cooling on a room by room basis. Call the professionals at Rush Maintenance Heating & Cooling for consultation for all your air conditioning needs.