Swamp Cooler Quick Guide -- An Overview on Evaporative Coolers

1. What is evaporative cooling?

Nature's most efficient means of cooling is through the evaporation of water. Evaporative cooling works on the principle of heat absorption by moisture evaporation. The evaporative cooler draws exterior air into special pads soaked with water, where the air is cooled by evaporation, and then circulated.

2. What choices of evaporative cooling do I have?

The range of commercial and industrial evaporative coolers available today is extensive, varying from commercial mobile coolers to large and fully ducted systems designed for commercial use.

3. Are evaporative coolers more suitable for specific climates?

Evaporative cooling is especially suited for areas where the air is hot and the humidity is low. However, in areas of higher humidity, there are many proven cost effective uses for evaporative cooling that make this the best choice. For example, industrial plants, commercial kitchens, laundry facilities, dry cleaners, greenhouses, places which utilize spot cooling (loading docks, warehouses, factories, construction sites, athletic events, workshops, garages, kennels), and areas using confinement farming (poultry ranches and hog/dairy farms).

4. What advantages does evaporative cooling have compared to a refrigerated cooling system?

Evaporative cooling will provide a substantial energy savings over refrigerated air units. The simplicity of the design allows for low maintenance requirements. The evaporative cooler will also provide fresh, filtered air. The outside air that has been cooled will blow the stale, inside air, out. With the substantial savings of energy and the constant changes in the air, the industrial/commercial evaporative cooler is ideally suited for area cooling or spot cooling of factories, laundries, churches, schools, agricultural/business areas, restaurants, and more.

5. What size evaporative cooler do I need?

Evaporative coolers are size-based on cubic feet per minute (CFM) of airflow. For sizing information on industrial/commercial coolers, the formulas are located in the specification charts of the cooler considered. When sizing an industrial or commercial cooler it is important to be job specific to include unusual heat loads and static pressures of the system design.

6. How do swamp/evaporative coolers work?

Swamp coolers are efficient and effective machines of cooling. As a direct replacement for air conditioning in dry climates, these coolers are an example of how we can work with nature. Being considerably less expensive than air conditioning, it almost seems that one is getting something for nothing when using a swamp cooler.

The way a swamp cooler operates is very simple. There is a low horsepower motor which pumps the water from the floor of the cooler to the top of the cooler, where it proceeds to fall down the sides and along porous filter pads. A second motor drives a fan which pulls air from the outside, through the cooler, and then pushes this out into the hot room. The significant cooling action results from the water evaporating as the air passes through it. Incidentally, the water level is kept constant with the help of a floating sphere, functioning similarly to the one in a toilet bowl. The hot air enters the cooler, where two small motors power nothing more than a fan and a pump in order to send cool air into the hot room.

The way the air is cooled in a swamp cooler is similar to the way evaporating sweat cools the human body. When a substance is perceived at a certain energy heat level, measured in temperature, there is really a distribution of varying levels of temperature throughout the molecules of the substance. This assortment of temperatures average out to the measured value. Most of the molecules can be around the average, and the farther from the average, the less of them there are. For example, water at room temperature has most of its molecules at approximately that temperature, but it also contains molecules that are near the boiling point of water and also near its freezing point. However small in quantity they are, these are an important presence. Because at the boiling point of water, there are molecules that are gases and those that are liquids. The liquid molecules will absorb energy in the form of heat to become gases and escape the confines of their old forms. As the molecules from the higher temperatures evaporate, the remaining liquids average less heat, but there will still be water at the higher temperatures because the remaining molecules redistribute themselves along the bell curve, enabling the next molecules to evaporate. Heat is siphoned off this way from the water, and more importantly, heat is extracted from the air as the liquid water at the boiling point grabs the needed energy for its freedom into gas.

An evaporative cooler produces effective cooling by combining a natural process--water evaporation--with a simple and reliable, air-moving system. Fresh, outside air is pulled through moist pads where it is cooled by evaporation and circulated through a house or building by a large blower. As this happens, the temperature of the outside air can be lowered as much as 30 degrees. Probably because evaporative coolers add moisture to the air and blow it around, they are sometimes known as "swamp coolers." Evaporative coolers can work wonderfully well, provided the outside air they are drawing in is dry and desert-like. As the humidity increases however, the ability for swamp coolers to cool the air effectively, decreases. Simply put, swamp coolers are not designed to work in swamp-like conditions.

Air conditioning on the other hand, became popular because of the ability to cool the air, not depending on the surrounding humidity. Even on humid days, room and central air conditioners can lower the temperature to a thermostatically-controlled temperature. Air conditioners also use as much as four times the electricity than a swamp cooler and are more expensive to install and maintain. Air conditioners can require ozone-damaging refrigerants, not to mention, circulating the same air over and over again. Fairly popular in desert areas, swamp coolers will work well in California's more humid climates for a majority of the time. Sacramento, for example, averages about 30% humidity on a typical, hot summer afternoon, while this is still dry enough for evaporative cooling to work effectively.

7. Why does evaporation lower temperature?

The process of evaporation happens all the time. Our bodies, for example, perspire in hot weather. Through evaporation, sweat dries and causes our body temperature to drop. Whenever dry air passes over water, some of the water will be absorbed by the air. That is why evaporative cooling naturally occurs near waterfalls, rivers, lakes and oceans. The hotter and drier the air, the more water that can be absorbed. This happens because the temperature and the vapor pressure of the water and the air attempt to equalize. Liquid water molecules become gas in the dry air, a process that uses energy to change its physical state. Heat moves from the higher temperature of the air to the lower temperature of the water, resulting in cooler air. Eventually the air becomes saturated, unable to hold anymore water, and evaporation ceases.

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