Evaporative Cooling System for broiler

Good article about Evaporative Cooling System for broiler

high air speed ? 2.5 m/s

Thanks Dr. Mehmood and Stanley

You both are correct. Air velocity is very important. At present the air speed is 3 m/s and main problem is in high humidity. When weather is hot and humid we put on cooling pads on timer because if you stop totally then inside shed temperature will rise continuously and you may have mortality. Even with putting pads on timer birds are not comfortable. The humidity inside house sometimes touches 90 % and temperature 34 C. In this situation the heat index is high and there is no wind chill effect. Birds start panting and loose production and hatchability. In this situation only air velocity is cannot solve problem. Waiting suggestion to improve the situation.

Best regards
Dr. Munawar Ali

Evaporative Cooling with Power Ventilation

Fogging nozzles and evaporative cooling pads are options that can be used in combination with power ventilation systems and especially with tunnel ventilation. Evaporative cooling uses heat from the air to vaporize water, increasing humidity but lowering air temperatures. Evaporative cooling can be effective in during the hottest part of most days because that is when humidity is lowest. On rare occasions the humidity remains high the entire day or immediately before or after a storm; evaporative cooling is ineffective under such conditions and should not be used.

Evaporative cooling pads operate on the same cooling principle as foggers, except that the air is cooled when it passes through the wet pads as it enters the house. This method avoids the problem of wet litter sometimes encountered with foggers, allowing evaporative cooling pads to be used on a continuous basis. Aspen fiber and corrugated cellulose are two materials widely used as cooling pads. Regular maintenance is necessary to ensure long life of the pads. First, the pads must be allowed to dry out once each day. They can be dried by turning off the water supply but allowing the fans to continue running. The best time to dry the pads is in the early morning hours when the outside temperature is relatively low. Drying allows the adhesive that holds the pad together to maintain its integrity and also helps reduce the buildup of algae. To further reduce the growth of algae, an algicide can be used in the water supplied to the cooling pads. Calcium hypochlorite, ethylene dichloride, or ammonium chloride can be administered at a rate of 6 ounces per thousand gallons of water, applied once each week. In addition, the pads should be washed monthly to remove dust and sediment. The entire system should be flushed monthly to remove the mineral salts and dirt that accumulate in the pipes and reservoir.

Evaporative pads constructed of aspen or cellulose ranging in thickness from 2 to 6 inches are being used in the industry in conjunction with power ventilation systems. On a hot, dry day these pads evaporate water at a rate up to 100 gallons per minute per hundred square feet of pad surface area. Using tunnel ventilation, they can evaporate up to 200 gallons per minute per hundred square feet of pad on a hot, dry day.

Fogging systems have also been used successfully in environmentally controlled poultry houses. Fogging systems that provide a reliable fine mist and that have water filters (to keep nozzles from clogging) and also have a positive shutoff to prevent dripping can provide successful cooling without causing wet litter. The water pressure should be at least 100 pounds per square inch (psi) to achieve a fine mist; a pressure 200 psi is preferred. The volume of water that goes through the fogging system and the number and placement of the nozzles are critical design considerations. A total flow rate of up to 1 gallon per hour per thousand cubic feet per minute (cfm) of ventilation can be used in tunnel-ventilated houses.

The design of the fogging system is critical for tunnel-ventilated houses. Cross lines of nozzles that provide a "curtain" of fog across the house at various intervals are fairly effective. Nozzles or lines of nozzles should be located close together near the air inlets, then spaced farther apart along the house, ending 60 feet from the exhaust fans. Tunnel-ventilated houses can use substantially more fogging capacity (50 to 100 percent more) than naturally ventilated houses because the forced air movement is able to carry the mist.

The value of a summer ventilation system should not be underestimated. If the system is operating properly, it can improve litter quality, reduce dust levels, and improve the flock's rate of gain or production level. The key to operating any ventilation system is understanding how it works. In addition, a good maintenance program of cleaning, adjusting, and monitoring controls for the curtains or inlets will maintain system efficiency. Fans in any ventilation system should be cleaned and lubricated frequently, and fan belts should be adjusted periodically, especially during times of heaviest use. If foggers are used, they should be serviced periodically to ensure that they produce a uniform, fine fog. If questions arise concerning the operation of your ventilation system, consult your flock supervisor.

Tunnel Ventilation
A new arrangement for ventilating poultry houses in the summer is tunnel ventilation. Simply put, this method involves moving air along the building axis from inlets to exhaust fans, providing high airflow velocities. This rapid air movement increases convective heat loss, reducing the effective temperature experienced by the birds. Most of the benefits of tunnel ventilation occur at an air velocity of 350 feet per minute. This velocity should be considered the minimum for most house designs. Tunnel ventilation systems do not operate on a static pressure difference. In fact, they work best when there is no pressure difference between the inlets and the fans.