Research and on-farm demonstrations have shown that micro-sprinklers, spray jets and fan cooling systems can be effective in relieving heat stress in dairy cows under hot, humid conditions. Based on these results, many dairymen are considering installing sprinkler and fan cooling. Several Kentucky dairymen have already installed sprinkler cooling systems, but they could improve their performance by modifying them to take into account the principles involved and the components used in sprinkler and fan cooling

Chastain, John P.

Turner, Larry W.

Warner, Richard C.

English

University of Kentucky

University of KentuckyUKnowledgeAgricultural Engineering Extension Publications Biosystems and Agricultural Engineering6-1992Micro-Sprinkler and Fan Cooling for Dairy Cows:Practical Design ConsiderationsLarry W. TurnerUniversity of KentuckyRichard C. WarnerUniversity of Kentucky, richard.warner@uky.eduJohn P. ChastainUniversity of KentuckyRight click to open a feedback form in a new tab to let us know how this document benefits you.Follow this and additional works at: https://uknowledge.uky.edu/aen_reportsPart of the Bioresource and Agricultural Engineering CommonsThis Report is brought to you for free and open access by the Biosystems and Agricultural Engineering at UKnowledge. It has been accepted forinclusion in Agricultural Engineering Extension Publications by an authorized administrator of UKnowledge. For more information, please contactUKnowledge@lsv.uky.edu.Repository CitationTurner, Larry W.; Warner, Richard C.; and Chastain, John P., "Micro-Sprinkler and Fan Cooling for Dairy Cows: Practical DesignConsiderations" (1992). Agricultural Engineering Extension Publications. 19.https://uknowledge.uky.edu/aen_reports/19The most economical cooling method is evaporativecooling using spray jets or mini-sprinklers and fans. Resultsfrom research at the University of Kentucky and elsewherehave given us improved design and operation guidelines forsuch systems.Sprinkler and Fan Cooling PrinciplesIn sprinkler and fan cooling, the sprinklers createdroplets that wet the cow’s hair coat to the skin. Fans arethen used to force air over the cow’s body (see Figure 1),causing evaporative cooling to take place on the skin andhair coat. Heat from the cow’s body causes the moisture toevaporate. The droplet size must be large enough to wet theskin surface and must be applied intermittently to allowtime for the moisture to evaporate from the skin. Airmovement is needed in fairly humid climates, such as thatin Kentucky, to provide enough drier air above the skin todo a good job of evaporating the water.Fog or mist systems (with very fine sprays) are notrecommended for dairy cattle in Kentucky because of thehumidity levels during the summer. Those systems attemptto cool the air around the cow rather than cooling her skindirectly. In the arid West this works well, but in morehumid areas, a “steam bath” effect can actually be created.Therefore, for the eastern and midwestern United States,sprinkler and fan cooling should be used rather than fogs ormists.Cooling BenefitsSeveral system designs and weather conditions havebeen studied for sprinkler and fan cooling systems. Systemstested in Kentucky and Florida, as well as in other loca-tions, have demonstrated the potential benefits. Feed intake,milk production and cow comfort have all been shown toincrease by using sprinkler and fan cooling. Currentresearch has reduced the amount of water used from 50-75gal/hd/day to as low as 6 gal/hd/day which reduces potentialherd health problems, such as mastitis.Research and on-farm demonstrations have shown thatmicro-sprinklers, spray jets and fan cooling systemscan be effective in relieving heat stress in dairy cows underhot, humid conditions. Based on these results, manydairymen are considering installing sprinkler and fancooling. Several Kentucky dairymen have already installedsprinkler cooling systems, but they could improve theirperformance by modifying them to take into account theprinciples involved and the components used in sprinklerand fan cooling.Heat Stress EffectsThe need for such systems arises from the effects of heatstress on dairy cows. The thermoneutral temperature range,or “comfort” zone, for most dairy cows is about 40-75oF.Above 75oF, increases in temperature and/or humidity beginto cause heat stress.Heat stress can reduce feed intake, milk production, andbreeding efficiency in dairy cows. Losses in the pocketbookfollow when milk production and breeding efficiency drop.Declines in milk production of as much as 25% have beenreported for summer conditions in the humid Southeast.Over a summer season (June 1-September 30) heat-stress-related losses can range from about 55 lb/cow in Maine toabout 1,000 lb/cow, or more, in Texas for a cow milking 66lb/day.Methods for Heat Stress Relief:Water, Shade and VentilationThere are several means available for reducing heatstress in dairy cows. Providing plenty of clean and availablewater, enough shade, and good ventilation should beroutine. These areas are the first places to concentrate if aheat stress problem is evident in the herd. Some type ofcooling system can then be considered after the moreroutine practices are taken care of.AEN-75Micro-sprinkler and Fan Cooling for Dairy Cows:Practical Design Considerationsby Larry W. Turner, Richard C. Warner and John P. ChastainAgricultural Engineering Department2Table 1 summarizes the benefits of sprinkler and fancooling found in several research trials conducted in theU.S. and Israel. Based on these trials, you could expectincreases in net income of 25-30 cents/cow/day after payingfor the increased feed costs, water, and electricity costs.With that amount of increased income, you can expect agood return on investment in the system for many areas ofthe eastern and midwestern United States. In Kentucky, thesystem will pay for itself in one year or less on many farms.Planning and Component SelectionSeveral commercial dairies in Kentucky, Florida andother locations have installed variations on the system,although some of the specific design questions and tech-niques are not yet well defined by research. If you areconsidering installing a sprinkler and fan system on yourdairy, there are some general design guidelines you shouldfollow in locating the system, selecting the nozzles and thefans, and ensuring a good water supply.Locating the System(s)For best results, the system should be located undershade. A shaded feed bunk (Figure 1) or the holding pen(Figure 2) are the two locations currently recommended inKentucky. Because of some concern over possible mastitisproblems, location of a sprinkler system in a free stall barnmay not be desirable, particularly if straw, sawdust or otherabsorbent bedding is used. Adequate drainage (1/8-1/4"/ftslope) is needed wherever the system is installed to avoidponding of water.Selecting the NozzlesThe most important aspect of selecting a nozzle type isto have a large enough droplet size to wet the cow’s skin.Irrigation nozzles and solid-cone coarse-droplet spraynozzles are desirable. Successful systems have beeninstalled using nozzle sizes ranging from 7 gph to 300 gph.A size range of 7 to 30 gph (0.12 to 0.5 gpm) per nozzle ispreferred to conserve water, reduce the total required flowrate and avoid runoff problems.Either 180° (half-circle) or 360° (full-circle) nozzlesmay be used. The 180° nozzles work well mounted next to afeed bunk, spraying away from the feed to help avoidwetting it. The 360° nozzles work well in a holding area.When choosing nozzles, take note of the pressure specifica-tions and spray pattern radius.The spray radius is used to determine the nozzle spacing.The pressure requirement indicates the operating pressuresuggested for a particular installation. For example, nozzlesthat have a 4 ft spray radius should be spaced no more than4 ft apart to achieve a relatively even distribution.Table 1: Summary of Test Results of Sprinkler and Fan Cooling of Dairy Cows.Control CooledResponse Measurement Group Group DifferenceFeed Intake (% change)Florida (dry matter) lb/day 39.2 41.0 +2.8 (+ 7.1%)Kentucky (as fed) lb/day 77.0 84.1 +7.1 (+ 9.2%)Missouri (as fed) lb/day 72.3 77.4 +5.1 (+ 7.1%)Milk Production (% change)Florida lb/day 39.8 44.4 +4.6 (+11.6%)Kentucky lb/day 50.1 58.0 +7.9 (+15.8%)Missouri lb/day 51.4 55.8 +4.4 (+ 8.6%)Israel lb/day 72.8 78.0 +5.2 (+ 7.1%)Rectal TemperatureKentucky (11 AM) °F 102.6 101.6 -1.0Missouri (PM) °F 102.6 101.8 -0.8Milk TemperatureMissouri °F 102.4 101.5 -0.9RespirationRate-Breath per minute(% change)Florida 96 57 -39 (-40.6%)Kentucky 91 75 -16 (-17.6%)3The recommended nozzle pressure for most spray jetsand micro-sprinklers is 20 to 25 psi. If the operatingpressure is too high, the droplet size will be reduced and theresulting mist will drift. Also, the smaller droplet will notpenetrate through the animal’s hair coat to the skin, andmuch less cooling will occur. Thus, as shown in Figure 3, apressure regulator should be installed in the system to limitthe required nozzle pressure to these recommended values.When selecting a spray jet or micro-sprinkler, considerthese factors:• nozzle size,• whether the nozzle spins or is stationary,• the type of spray pattern, i.e., stream or fan,• flow rate,• radius, and• recommended operating pressure.Both the flow rate and spray radius will increase as thenozzle opening and operating pressure increase.FAN / TUBE SYSTEMFigure 24Water Supply and Pipe RequirementsThe water supply can be a municipal system, pond, wellor other farm source. If a farm source is used, a filter and/orwater treatment unit may be needed (see Figure 3). A 140 to155 mesh filter is recommended for most applications. Thewater system must be able to deliver the flow rate needed tosupply all of the nozzles operating at a given time.If the low volume-low pressure spray jets are used, waterdelivery is not a problem. For example, a system for a 96 ftfeed bunk which has 18 nozzles spaced approximately 5 ftapart, each delivering 7.5 gph, would require about 2 gpm.If nozzles were on both sides of the bunk, running at thesame time, 4 gpm would be required.That requirement would be in addition to any other waterneeds at the same time on the dairy for watering, cleaning,etc. For example, if nozzles delivering 1 gpm with a 12 ftspacing were used, then a total flow rate of 16 gpm wouldbe needed, which may exceed the flow expected through astandard household water meter. Table 2 lists flow rates forstandard water meters commonly used on farmsteads.Both PVC (rigid white plastic pipe) and PE (blackplastic pipe) are used in several installations. The smallerdiameter(1/2" to 3/4") black plastic pipe, which is less costly, shouldcontain 2% or higher carbon black and an anti-oxidant toprevent degradation from sunlight and oxidation. Also, PEpipe simplifies the installation and requires less fittings.The pipe size requirement will vary for each systembased on the selected spray jet or micro-sprinkler and theoperating pressure. Safe flow rates for PVC and PE pipesused for water conveyance are listed in Table 3.For the feed bunk pipe, where water is being dischargedthroughout the pipe length by evenly spaced spray jets ormicro-sprinklers, a 1/2" PE pipe conveying 4 gpm will havean overall pressure loss over the 100 ft length of approxi-mately 4 psi. This will produce only an 8% change innozzle discharge for most micro-sprinklers.5A filter is recommended for many applications; an in-line plastic or stainless steel 140 to 155 mesh filter willperform well (see Figure 3). Sand or centrifugal filters maybe required if a large amount of sediment is present in thewater supply.Selecting FansAir movement in the velocity range of 200 ft to 400 ftper minute across the cows is needed. However, the airmovement at the cow level depends on the dischargecharacteristics of the fan and the distance of the cow fromthe fan.Fan/tube systems have been successfully used in Ken-tucky to provide the required air movement. They should besized to provide 150 to 250 cubic feet per minute (cfm) ofair flow per cow. For tubes mounted high above the cows, aflow rate of as much as 400 cfm/cow may be needed. If thetube is installed outdoors or in reach of the cows, then arigid or semi-rigid duct should be used to prevent damage.Hole size and spacing in the tube or duct can be determinedby the manufacturer or dealer once the air flow requirementis set.Large diameter rigid tubes can become costly and maynot be readily available. More information is available onpoly-tube systems in the University of Kentucky Coopera-tive Extension publication AEN-7 Poly-tube Heating-Ventilation Systems and Equipment.Another type of fan often used, particularly in holdingpens or other areas with higher eave heights, is a 1/2-hp 36"fan. Such fans will blow about 10,000 to 11,000 cfm with a“throw” distance of about 30 ft. A 1-hp 48" fan will provide21,000 cfm with an effective throw distance of about 40 ft.These fans should be mounted out of reach of the cows andangled downward slightly.Overhead paddle fans can also be used to provideairflow, but they offer limited air movement unless cows aredirectly under a fan. The paddle fans do have much higherefficiencies of operation, with ratings of 100 cfm/watt ofpower input, as compared to 15 to 20 cfm/watt for conven-tional propeller-type fans.Controls are a KeyThe controls are a key part of the system for assuring themost effective cooling. A thermostat is required to controlthe sprinkler and fan. The system should begin coolingwhen the temperature reaches 78°F. The fans should runcontinuously whenever the system is on. An adjustabletimer with a 30-minute cycle should be used to control thesprinkler interval. In the feed bunk area, an “ON” time of 1to 3 minutes in each 10 to 15 minutes is recommended. Forthe holding area, use a slightly longer “ON” time and ashorter “OFF” time than in the feed bunk system.A solenoid valve (electrically activated valve) is neces-sary to turn the water ON and OFF. The valve diametershould be the same as the sprinkler water line.The goal for controlling the cooling system should be toadjust the timer so that the sprinklers wet the cows to theskin, the spray shuts OFF, and then the water evaporatesuntil the hair coat is only slightly damp. The timer thenshould start the process over as long as the thermostatsenses a temperature above the set point.Assembling ComponentsMost of the components of a sprinkler and fan systemare available from irrigation suppliers or electrical andhardware stores. Package systems (except for fans) can alsobe bought commercially. The fans can be purchased fromfarm supply stores or catalogs. If a neighbor is using asprinkler system, ask him about improvements or changeshe would make. Most importantly, include the basicprinciples needed for a workable and successful system:intermittent sprinkling, large droplet size and air movementwith fans.Costs and Benefits of the SystemBased on field demonstration work and the results ofresearch, costs and benefits can be estimated for micro-sprinkler and fan cooling. Table 4 indicates cost estimatesfor installation and operation of the system for a 48-cowherd in Kentucky over an 800-hour run-time season. Usingthese cost estimates, the total system would cost $33.50/cow to install.Table 2: Flow Rate through Standard Water Meters.Size of  Size ofWater Service Gallons per Minute at Static Pressure (psi)Meter Line 30 45 60 755/8" 3/4"  4  8 11 143/4" 3/4"  6 10 14 173/4" 1"  8 14 18 211" 1" 10 17 24 28Table 3. Recommended DesignFlow Rates (gpm).Size PVC PE1/2  5  43/4 10 101 16 16For large-scale systems, some economy of scale wouldbe possible to reduce the cost per cow. Table 5 gives asummary of payback potential for the system. These costestimates indicate the system has potential to pay back inslightly more than one season of operation in Kentucky,based on milk production benefits alone, for a 100-day heatstress season.Potential Herd Health ConcernsResearch trials of fan and sprinkler cooling system havenot shown increases in mastitis for cooled cows. However,more research is needed to examine this aspect of thecooling system. If the area where the water is applied doesnot drain well, cows may lie in ponded water and couldhave an increased likelihood of mastitis.In on-farm tests, no incidences of mastitis in excess of“normal” occurrences have been documented for either feedbunk or holding pen installations. However, concern stillexists, and it is currently recommended that the system notbe used in a free stall barn other than in the area of acovered, in-barn feed alley.Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, C. Oran Little, Director of CooperativeExtension Service, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 1997 by the University of Kentucky CooperativeExtension Service. This publication may be reproduced in portions or its entirety for educational or non-profit purposes only. Permitted users shall give credit to the author(s) andinclude this copyright notice.Issued 6-92, 1.5MTable 5: Simple Payback for Forced EvaporativeCooling System*.Milk Value(Cents/Cow/Day) Costs (Cents/Cow/Day)50 Feed 19Spray Water  1Fan Energy  1Drinking Water  2Total Cost 23Net Income = 27¢/cow/daySimple Pay Back = 124 Days*Assuming increased feed intake of 5 to 6 lb/cow/dayand increased milk yield of 4 lb/cow/day.Qualitative AssessmentsConversations with dairymen involved in the detaileddemonstrations, as well as in dairy operations in otherinstallations in Kentucky, indicate they are pleased with theperformance of the system. The cows are attracted to thebunk more readily when the system is in place and operat-ing during hot weather. Limited performance data areavailable for evaluation of the benefits of the system oncommercial Kentucky dairies, but general impressions ofperformance benefits are positive.With respect to nozzle types and sizes, spray intervals,and system performance for optimal cooling and conserva-tion of water, many questions remain. Current research atthe University of Kentucky and other institutions shouldenable refinements and improved specifications to bedeveloped. However, dairymen do not need to wait forthese refinements to install a system. The positive benefitshave already been demonstrated, and any additionalresearch information should be easily adapted to an existingsystem.If you have questions or need additional informationabout micro-sprinkler and fan cooling, contact your countyExtension office. A videotape illustrating the system isavailable through the office, and additional details may beobtained by your County Agricultural Agent through theAgricultural Engineering Department at the University ofKentucky.Table 4: Estimated Forced Evaporative CoolingSystem Costs for a 48-Cow Milking Herd.Item Cost30" Diameter, 1 HP fan $ 61530" Rigid Duct, 50' long  200Thermostat  36Duct Hangers and Wiring  80Timer  50Solenoid Valve + Coil  481/2" Plastic Pipe, 100'  1518 Plastic Nozzles, 180°  21Mounts, Fittings, Filter, Etc.  45Labor for Installation (estimated)  500Total Investment Cost $1,610Operating Costs*Water Cost430 Gal/Cow/Season or $51 @ 25¢/100 Gal. =>l¢/Cow/DayElectricity Cost16.7 kWh/Cow/Season or $52 @ 6.5¢ kWh =>l¢/Cow/Day*Assuming 800 hours of run time over the season.

Micro-Sprinkler and Fan Cooling for Dairy Cows: Practical Design Considerations

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Micro-Sprinkler and Fan Cooling for Dairy Cows: Practical Design Considerations

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