design of desert cooler

A Desert cooler is a device used for the humidification and cooling of air.

Humidification is achieved by spraying droplets of water into the air stream thus increasing moisture content of the air.

Cooling is achieved, by ensuring that the water temp is less than the DBT of air. As a result, the water absorbs the letent heat of vaporistaion from the air, thus reducing its temp. With this reduction in air temp, the body temp of the person in the path of the air also reduces.

Specifyig the design procedure is not possible here, but you must design a mechanism to produce an air stream into the area to be cooled. You must also design a mecanism to either spray a mist of cool air or let the air passed through a moist wick before entering the room to be cooled. Actually design a rudimentary but effective desert cooler is a no-brainer.

what is DBT of air ?

Ans: DBT is Dry Bulb Temp.

"what temperature should be of water ........"

Ans: The Temp. of water"sprayed should be "AS CLOSE AS POSSIBLE TO THE WET BULB TEMP." Possibly water Temp. will be just below room temp. Wet Bulb Temp. is measured by a Sling Thermometer by wetting the cotton swab.

If sling thermometer is not available, take a thermometer and put a wetted cotton swab and dip the other end of the cotton swab in a small beaker of water. The measurement of Wet Bulb should be atleast 10 Metres away from any building.

Lower the Wet Bulb Temp., Higher will be the water vapour absorbed - to get the air saturated or nearing saturation, and hence more cooler will be the air.

If the air is saturated, or near saturation, the cooling of air will be less or nil.

DHAYANANDHAN.S

if i spray droplets of water at 70 degress and mass flow rate of water sprayed is 1kg/s. And the water mix with air stream which is 20 degrees and 40% relative humidity. how do i calculate the increase in moisture content of the air?

It depends upon the quantity of air - flow rate and you have to indicate the quantity of air flow.

DHAYANANDHAN.S

These are also known as evaporative coolers, and are common in the Sothwestern US as an alternaitve to regular AC.

http://en.wikipedia.org/wiki/Evaporative_cooler

Here's an illustration of the insides of the type commonly seen in residential use:

The bottom serves as a reservoir for water. A pump lifts the water so it runs down through the filters on 3 sides. An electic motor drives a squirrel-cage fan that draws air through the filters and pushes it into the room to be cooled.

Shortcomings are the need to refill the water supply, noise, rust, birds picking out the straw used for the filter material, and if the birds succeed, bugs being blown inside. I know these things from experience.

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