Evaporative Cooling Systems

Transcription

1 Volume 5, Number 2 Quarterly Publication of Cobb-Vantress, Incorporated Summer 1997 Evaporative Cooling Systems Understanding and Maximizing Summer Ventilation - by Robert Barnwell As the summer months approach, breeder and pullet technicians and their growers are preparing for the struggle with hot weather conditions. Achieving and maintaining good production levels during this time of the year is one of the major challenges facing breeder departments around the world. Allow CVI to visit with you concerning some key areas of summer ventilation that may ease the burden of stress on your birds during this year s season. High temperature is only one part of the summer equation that service staff must deal with. The combination of this high temperature along with high relative humidity is the critical issue. The heat index (temperature and humidity factor) is what production personnel should keep in mind when managing their flocks. Heat index can be defined as the addition of temperature in fahrenheit and relative humidity. If, when added together, the total of these two factors is greater than 160, there is a heat index that is detrimental to bird performance. All chickens struggle in these conditions, so it is not hard to realize that broiler breeders in production may be the most susceptible to the hot weather stress. Tunnel ventilation with evaporative cooling is the most popular type of system used for the control of heat stress on breeders today. If evaporative cooling systems are installed, maintained, and managed properly they will provide adequate environments for your flocks. The first priority of summer ventilation is air velocity at bird level. Air movement is very important to the bird s ability to dissipate heat into the environment. The second priority is the air exchange rate in the house which is critical to maintaining adequate oxygen levels. With evaporative cooling systems air velocities of three hundred to four hundred feet per minute ( f.p.m.) are needed. The ideal velocity would be 350 f.p.m. through the house. The air exchange rate should range from.75 to 1.3 minutes, with 1 air exchange every minute being the ideal. The fan capacity (as required to achieve the desired air velocity and exchange) must always be matched with the pad space. Whenever the air speed through the pads is too fast the evaporative efficiency will not be good and moisture will be pulled into the house. Likewise if the air speed is too slow then the temperature drop will be less than desired. The air speed through a six inch pad should be 400 f.p.m. and the speed should be 250 f.p.m. through a four inch pad. However, these speeds will create only a negative pressure of in the house. This pressure is not great enough to provide uniform airflow throughout the house from sidewall to sidewall. The negative pressure in a forty foot wide house should be.05. To achieve this pressure, air must enter the house at the equivalent

2 of 900 f.p.m. A method of accomplishing this is using a curtain between the pads and house to restrict the inlet space at the entrance to the house. This forces the air speed entering the house (after going through the pad at the proper speed) to increase. This is an important point to monitor in tunnel ventilation houses. If the system is going to achieve adequate efficiency, it must operate at the proper pressure and have air speed entering the house at the proper velocity for the width of the house. The fan controls should be set to stage their volume up and down with the temperature changes. It is important to remember air velocity and inlet openings must change as fans stage up and down. The water pumps should operate only after all the fans have staged on. The pumps should never run continuously. The pumps need a dual control for temperature and humidity. It is important to remember that the environmental challenge is the heat index (temperature and humidity) not just temperature. Adding moisture in the house by running the pad pumps too much works against the goal of the system. An important point to mention while talking about the heat index is staging fans down in the evening or early morning based on thermostats only. Many times the heat index might be high due to elevated humidity during these periods but the temperature alone may dictate a bank of fans to shut off. Remember that managing heat stress requires alleviating both high temperatures and high humidity. Air velocity across the birds may still be needed during the times of day when humidity is highest. The only way to lower humidity is by creating evaporation. Maintenance of the evaporative cooling systems is necessary to keep efficient operation. Fan speeds and air volumes must be monitored. Belts should be tight and shutters should be cleaned. At the start of each season, a surfactant should be added to the pump tank. To help clean the pad pores the pumps should be run for four hours without air moving through the pads. Once this is done, clean the pump tank and begin normal operation. For long pad life and also to keep efficiency high, the system should be purged on a regular basis. The easiest way to accomplish this is to put a hose bib on the end of the solids trap. Once a week open the faucet and draw five gallons of water and discard it somewhere away from the house. If there is not a solids trap or purge line on your system there should be one installed before hot weather use. Lastly, it is important to ensure that the pads have been installed properly. If the pad is an odd angle design, the greater angle must be down and to the outside of the house. If it is installed differently, it will cause water to enter the house and a good temperature drop will not take place. In summary: 1) Maintain adequate air speed. Calculate the cubic volume of air to be moved in the house. Divide the house length by the desired air velocity for the necessary air exchange. Divide cubic air volume by the air exchange and the necessary c.f.m. s of fans needed can be calculated. 2) Air exchange ( minutes). 3) Temperature drop in the house. Temperature drop with air velocity creates the wind chill effect and lowers the effective temperature the birds will actually feel. Ideal effective conditions for heavy breeders is 68 and 50% RH. 4) Control of relative humidity. There must be a high level of evaporation to control humidity. It takes heat and air velocity to create evaporation. 5) House pressure must be maintained. In a forty foot wide house,.05 negative pressure is needed, yet the speed through the pads is based on their thickness. Remember to manage inlet space with a curtain. 6) Provide proper maintenance. If you follow these priorities, you should position your flocks to be efficient producers even in the face of hot weather stress. 2

3 Table 1 Effective Temperatures Actual Temperature Relative Humidity Air Velocity Feet Per Minute F C 50% 70% % % % % % % 32.2% % % % % % % % % % % % % % % % % % % Anytime the air speed exceeds 500 feet per minute the effective temperature begins to increase again instead of decreasing because the potential evaporation rate of moisture begins to diminish. The moisture begins to move with the airflow instead of vaporizing and allowing for evaporation from the heat source and air velocity. For metabolism from feed and water intake the ideal conditions are 50% relative humidity (45%-65% limits) and 68 to 70 degrees F (20 to 21.1C). When the moisture holding capacity of the air reaches dew point an increase in humidity above that will create a heat index, therefore the effective temperature is greater than the actual temperature. 3

4 The CVI Technical Service Team Six years ago CVI charted a course towards providing technical service to our customers. CVI committed itself...to provide the technical service and support needed to maximize the full genetic potential of the Cobb 500. At the time we had two representatives in the U.S. market and one in the South American region. In the six years that have passed CVI has formed a technical team that is second to none in the industry. We would like to re-introduce them to you. Our U.S. customer base is now split between four representatives. The domestic team frequently gets together and compares notes on management and equipment developments to allow their customers to stay abreast of their rapidly changing industry. The demand for the Cobb 500 across the world required rapid expansion in our international technical staff. CVI s overseas representatives bring their unique perspectives and experiences to our group discussions, which allows for a broader base of information. UNITED STATES Joel Truitt - SW - Siloam Springs Bob Carlson - SE - Gainesville Pete Sbanotto - SW - Siloam Springs Chris O Brien - SE - Gainesville 4

5 The CVI Technical Service Team CVI has the good fortune to have some very fine specialized technicians on its team. Dr. Ken Powell s experiences with physiology and metabolism, while at Oklahoma State University and Hoffman La Roche, are unique to the breeding industry. Likewise, Dr. Chet Weirnusz also studied physiology and metabolism at Oklahoma State while pursuing his doctorate in nutrition. Together these gentlemen will keep CVI on the cutting edge in research and in developing management systems to maximize the Cobb 500 s genetic potential. INTERNATIONAL Jose Manduca - S.A. Tech Mgr. - Brazil Jairo Arenázio - S.A. - Brazil Philip Fausto - S.A. - Brazil P. Hundl - Mexico Aziz Sacranie - Asian Tech Manager - Scotland 5

6 SPECIALIZED SUPPORT Robert Barnwell is the newest member of our team and needs little introduction. (He has been traveling the world for several years helping production personnel improve their ventilation systems.) CVI is excited to have Robert join our group and be available to help our customers design houses and facilities for efficient production, as well as trouble shoot problems when they occur. At CVI, we feel we have a technical team in place that will position us to meet the challenges we put to ourselves six years ago. CVI holds firm to the vision put forward at that time. Robert Barnwell - Vent Specialist - Texas Dr. Ken Powell - DVM - Siloam Springs Dr. Chet Weirnusz - Nutritionist - Siloam Springs About the Author: Robert Barnwell was born on August 9, 1941 in Pittsburg, Texas. He was raised on a poultry farm and graduated from Pittsburg High School, where he was active in FFA, receiving all the FFA awards offered. After being president of the Texas Young Farmers for four years, he was employed by Pilgrim s Pride Corporation for sixteen years where he worked his way up from hatchery, production, feed mill, protein conversion, and processing to senior vice president. After owning a poultry and livestock distributorship for six years, he was regional sales manager for four years for Big Dutchman/Cyclone. He currently lives in Pittsburg where he owns and operates a private consulting company, working worldwide on poultry and swine ventilation, production and management. Today, our product, services and support are better than ever before! Tomorrow, we will be better still. You (our customer) can hold us to it. Cobb-Vantress, Inc. P.O. Box 1030 Siloam Springs, Arkansas (501) FAX (501)