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A Procedure for Determining Poultry House Ventilation
A Procedure for Determining Poultry House Ventilation F. N. REECE and B. D. LOTT US Department of Agriculture, ARS, South Central Poultry Research Laboratory, Mississippi State, Mississippi 39762 (Received for publication September 12, 1983) ABSTRACT Simplifying assumptions have been made which permit relating climatic conditions to specific atmospheric humidity so that routine determination of ventilation rates for broiler chicken houses can be made. A simple computer program, suitable for use on inexpensive computers, is described. (Key words: environment, brooding, ventilation, computer, broilers) 1984 Poultry Science 63:1076-1078
INTRODUCTION An important part of the management of production facilities where poultry are grown on litter is the maintenance of the litter so that levels of pathogenic organisms, dust, and ammonia in the environment are within acceptable limits. Although factors such as stocking rate, size, and litter materials affect litter conditions, the basic parameters used by managers to control litter condition is the relative humidity (RH) in the house. Reece and Lott (1982a) suggest that RH in the 50 to 70% range will maintain the litter in a broiler house in acceptable condition; litter moisture should be in the 20 to 30% (wet basis) range. The mathematical equation used to determine the ventilation rate to maintain a specific RH in a poultry house is relatively simple (Reece and Lott, 1982b). It balances the moisture produced by the birds, including both respiratory and fecal evaporation, with the moisture content of the incoming (outside) air and that of the outgoing (exhaust) air so that the RH in the house is within acceptable limits. PROCEDURE FOR CALCULATIONS OF POULTRY HOUSE VENTILATION To determine the ventilation rate for a poultry house at any given time, it is necessary to determine the following parameters: 1) specific humidity, in weight of water per unit weight of dry air, of the incoming ventilation (outside) air; 2) specific humidity, in weight of water per unit weight of dry air, of the exhaust ventilation air; and 3) total amount of moisture given off by the chickens.
To determine the specific humidity of the outside air, the dewpoint temperature of air can be directly translated into specific humidity by the equation: W = 2 . 0 2 7 e ( 1 + 0 3 8 t ) + .005833t 2 + .04733t where: W = specific humidity, grains moisture/lb dry air, t = dewpoint temperature, F, e = base of natural logairthms, 2.7183. Use of dewpoint temperature to determine specific humidity avoids the problems associated with secondary measurements such as RH or wet-bulb temperature. Furthermore, in climates where dew formation at night is common, dewpoint temperature can be rather accurately estimated daily by observing the minimum dry-bulb temperature. The procedure described here estimates the specific humidity of the incoming ventilation (outside) air by assuming that the dewpoint temperature of the outside air is equal to the 0600 hr dry-bulb temperature each day. Litter moisture content is controlled by the RH in the poultry house; RH maintained in the 50 to 70% range results in a litter moisture of 20 to 30% (wet basis). Therefore, it is essential to control the ventilation rate so that the specific humidity of the exhaust air, which is most conveniently measured by dewpoint temperature, is such that proper RH is maintained.
1076
RESEARCH NOTE
Because dry-bulb temperature is controlled rather precisely in poultry houses, especially during brooding, it has been found that deducing dewpoint temperature from the drybulb temperature and RH relationship is an acceptable method of determining specific humidity of the exhaust air. For the range of conditions normally encountered in a poultry house, this can be done by the equation-.1 t = DB - (44.2 - .48R) where: t = dewpoint temperature, F, DB = dry-bulb temperature, F, in 60 to 90 F (15.6-32.2 C) range, R = % RH in 50 to 70% range. The third part of our equation is the calculation of the total amount of moisture produced by chickens. To determine the amount of moisture that must be removed from the poultry house, the following parameters must be known: 1) number of chickens; 2) size of chickens; and 3) amount of moisture produced per unit of body weight in respired air and from feces. The moisture production data for broiler chickens (1982a,b) and mathematical equations for growth of broiler chickens have been reported by Reece and Lott (1982d). Therefore, mathematical equations are available to determine the amount of moisture produced by broiler chickens for ages from 0 to 49 days. The relationships discussed above were used to develop a simple computer program for calculating the ventilation of broiler chicken houses. The program can be used with practically any inexpensive computer that can be programmed in BASIC language: 10 20 30 40 50 60 70 80
INPUT"0600 H R T E M P , F " ; X INPUT"INSIDETEMP,F";Y INPUT"BIRDNO";N INPUT'BIRD AGE";D INPUT"INSIDE RH";R Z=Y-(44.2-.48*R) IF Z < = X T H E N R=R+5:IF Z < = X T H E N 60 IF R > 9 4 T H E N 270
90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280
1077
A=(2.027*EXP(1+.038*Z)+.005833»Z~2+ .04733 *Z)/7000 B=(2.027*EXP(1+.038*X)+.005833*X~2+ .04733 • X l / 7 0 0 0 IF D < = 2 3 T H E N 130 G O T O 150 W=.04+6.91*D*10 - 3 + 1 . 2 7 * D " 2 » 1 0 " - 4 + 2.04»D"3*10~-5 G O T O 160 W=.0532*D-.71 IF W < . 1 3 T H E N 190 IF W X 5 T H E N 230 GO TO 210 V=N*.227/(A-B)*(69.69*W"4-25.97»W"3+ 3.104»W"2-.0716*W) GO TO 240 V=N«.227/(A-B)»(-.2597»V\f4+.4223'W"3.2334»W~2+.0695*W) GO TO 240 V=N».227/(A-B)»(.007792«W~5-.04012*W~4+ .07919*W~3-.08067*W"2+.05448'W) PRINT " R E L A T I V E H U M I D I T Y = " ; R PRINT " V E N T I L A T I O N , c f m = " ; V GO TO 280 PRINT " W A R M , H U M I D ; USE M A X V E N T ; RH=";R END
To use the program for metric units, substitute the following lines for the lines indicated: 10 INPUT"0600 HR T E M P , C " ; X C : X = ( 9 * X C / 5 ) + 3 2 20 INPUT'MNSIDE T E M P , C " ; Y C : Y = ( 9 * Y C / 5 ) + 3 2 250 P R I N T " V E N T I L A T I O N , CUBIC M / H R " ; V * 1 . 6 9
Example calculations for three sets of conditions are as follows: 0600 HR TEMP? 40 F (4.4 C) INSIDE TEMP? 85 F (29.4 C) BIRD N O ? 1 BIRD A G E ? 5 INSIDE R H ? 6 0 R E L A T I V E H U M I D I T Y = 60 V E N T I L A T I O N , f t 3 / m i n .081 (.138 m 3 /hr) 0600 HR TEMP? 60.1 F (15.6 C) INSIDE TEMP? 70 F (21.1 C) B I R D NO? 10,000 BIRD AGE? 25 INSIDE R H ? 6 0 R E L A T I V E H U M I D I T Y = 75 V E N T I L A T I O N , f t 3 / m i n 53,295 (90,126 m 3 /hr) 0600 HR TEMP? 69 F (20.6 C) INSIDE T E M P ? 7 0 F (21.1 C) BIRD N O ? 1 BIRD AGE? 15 INSIDE R H ? 5 0 WARM, HUMID; USE M A X V E N T ; R H = 9 5
Definition of terms used in program are: 1
Linearization of the nonlinear humidity-temperature relationship results in an error in dewpoint temperature that does not exceed approximately 1.2 F (.67 C) for the range of conditions indicated.
X = Minimum daily temperature dewpoint temperature, F; Y = Temperature in house, F;
= outside
1078
REECE AND LOTT
N D R Z A
= Number of birds in house; = Bird age in days; = Inside RH, %; = Inside dewpoint temperature, F; = Outside specific humidity, pounds moisture per pound dry air; B = Inside specific humidity, pounds moisture per pound dry air; W = Chicken weight, kg; V = Ventilation rate for house, ft 3 /min (m 3 /hr) In the second example given, the desired RH of 60% cannot be maintained by ventilation alone. Therefore, reiterations are performed, each with an increase of RH in 5% increments, until a solution is obtained. In this example, the resulting RH was 75%. In the third example, no solution is possible, even with RH of 95%; this is indicated by the "WARM, HUMID; USE MAX VENT; RH=95" response. The program has been used with excellent results to adjust the ventilation rate for broiler
research houses at South Central Poultry Research Laboratory. It is used daily during the brooding and growing phase to adjust the ventilation fans. Normally, it is used in the morning of each day shortly after the 0600 hr minimum daily temperature has been observed, and the adjustment made at that time is retained for the enusing 24 hr.
REFERENCES Reece, F. R, and B. D. Lott, 1982a. Heat and moisture production of broiler chickens during brooding. Poultry Sci. 61:661—666. Reece, F. N., and B. D. Lott, 1982b. Optimizing poultry house design for broiler chickens. Poultry Sci. 61:25-32. Reece, F. R, and B. D. Lott, 1982c. The effect of environmental temperature on sensible and latent heat production of broiler chickens. Poultry Sci. 61:1590-1593. Reece, F. R, and B. D. Lott, 1982d. Typical broiler chicken growth rates, 1981. Poultry Sci. 61: 1013-1014.
INTRODUCTION An important part of the management of production facilities where poultry are grown on litter is the maintenance of the litter so that levels of pathogenic organisms, dust, and ammonia in the environment are within acceptable limits. Although factors such as stocking rate, size, and litter materials affect litter conditions, the basic parameters used by managers to control litter condition is the relative humidity (RH) in the house. Reece and Lott (1982a) suggest that RH in the 50 to 70% range will maintain the litter in a broiler house in acceptable condition; litter moisture should be in the 20 to 30% (wet basis) range. The mathematical equation used to determine the ventilation rate to maintain a specific RH in a poultry house is relatively simple (Reece and Lott, 1982b). It balances the moisture produced by the birds, including both respiratory and fecal evaporation, with the moisture content of the incoming (outside) air and that of the outgoing (exhaust) air so that the RH in the house is within acceptable limits. PROCEDURE FOR CALCULATIONS OF POULTRY HOUSE VENTILATION To determine the ventilation rate for a poultry house at any given time, it is necessary to determine the following parameters: 1) specific humidity, in weight of water per unit weight of dry air, of the incoming ventilation (outside) air; 2) specific humidity, in weight of water per unit weight of dry air, of the exhaust ventilation air; and 3) total amount of moisture given off by the chickens.
To determine the specific humidity of the outside air, the dewpoint temperature of air can be directly translated into specific humidity by the equation: W = 2 . 0 2 7 e ( 1 + 0 3 8 t ) + .005833t 2 + .04733t where: W = specific humidity, grains moisture/lb dry air, t = dewpoint temperature, F, e = base of natural logairthms, 2.7183. Use of dewpoint temperature to determine specific humidity avoids the problems associated with secondary measurements such as RH or wet-bulb temperature. Furthermore, in climates where dew formation at night is common, dewpoint temperature can be rather accurately estimated daily by observing the minimum dry-bulb temperature. The procedure described here estimates the specific humidity of the incoming ventilation (outside) air by assuming that the dewpoint temperature of the outside air is equal to the 0600 hr dry-bulb temperature each day. Litter moisture content is controlled by the RH in the poultry house; RH maintained in the 50 to 70% range results in a litter moisture of 20 to 30% (wet basis). Therefore, it is essential to control the ventilation rate so that the specific humidity of the exhaust air, which is most conveniently measured by dewpoint temperature, is such that proper RH is maintained.
1076
RESEARCH NOTE
Because dry-bulb temperature is controlled rather precisely in poultry houses, especially during brooding, it has been found that deducing dewpoint temperature from the drybulb temperature and RH relationship is an acceptable method of determining specific humidity of the exhaust air. For the range of conditions normally encountered in a poultry house, this can be done by the equation-.1 t = DB - (44.2 - .48R) where: t = dewpoint temperature, F, DB = dry-bulb temperature, F, in 60 to 90 F (15.6-32.2 C) range, R = % RH in 50 to 70% range. The third part of our equation is the calculation of the total amount of moisture produced by chickens. To determine the amount of moisture that must be removed from the poultry house, the following parameters must be known: 1) number of chickens; 2) size of chickens; and 3) amount of moisture produced per unit of body weight in respired air and from feces. The moisture production data for broiler chickens (1982a,b) and mathematical equations for growth of broiler chickens have been reported by Reece and Lott (1982d). Therefore, mathematical equations are available to determine the amount of moisture produced by broiler chickens for ages from 0 to 49 days. The relationships discussed above were used to develop a simple computer program for calculating the ventilation of broiler chicken houses. The program can be used with practically any inexpensive computer that can be programmed in BASIC language: 10 20 30 40 50 60 70 80
INPUT"0600 H R T E M P , F " ; X INPUT"INSIDETEMP,F";Y INPUT"BIRDNO";N INPUT'BIRD AGE";D INPUT"INSIDE RH";R Z=Y-(44.2-.48*R) IF Z < = X T H E N R=R+5:IF Z < = X T H E N 60 IF R > 9 4 T H E N 270
90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280
1077
A=(2.027*EXP(1+.038*Z)+.005833»Z~2+ .04733 *Z)/7000 B=(2.027*EXP(1+.038*X)+.005833*X~2+ .04733 • X l / 7 0 0 0 IF D < = 2 3 T H E N 130 G O T O 150 W=.04+6.91*D*10 - 3 + 1 . 2 7 * D " 2 » 1 0 " - 4 + 2.04»D"3*10~-5 G O T O 160 W=.0532*D-.71 IF W < . 1 3 T H E N 190 IF W X 5 T H E N 230 GO TO 210 V=N*.227/(A-B)*(69.69*W"4-25.97»W"3+ 3.104»W"2-.0716*W) GO TO 240 V=N«.227/(A-B)»(-.2597»V\f4+.4223'W"3.2334»W~2+.0695*W) GO TO 240 V=N».227/(A-B)»(.007792«W~5-.04012*W~4+ .07919*W~3-.08067*W"2+.05448'W) PRINT " R E L A T I V E H U M I D I T Y = " ; R PRINT " V E N T I L A T I O N , c f m = " ; V GO TO 280 PRINT " W A R M , H U M I D ; USE M A X V E N T ; RH=";R END
To use the program for metric units, substitute the following lines for the lines indicated: 10 INPUT"0600 HR T E M P , C " ; X C : X = ( 9 * X C / 5 ) + 3 2 20 INPUT'MNSIDE T E M P , C " ; Y C : Y = ( 9 * Y C / 5 ) + 3 2 250 P R I N T " V E N T I L A T I O N , CUBIC M / H R " ; V * 1 . 6 9
Example calculations for three sets of conditions are as follows: 0600 HR TEMP? 40 F (4.4 C) INSIDE TEMP? 85 F (29.4 C) BIRD N O ? 1 BIRD A G E ? 5 INSIDE R H ? 6 0 R E L A T I V E H U M I D I T Y = 60 V E N T I L A T I O N , f t 3 / m i n .081 (.138 m 3 /hr) 0600 HR TEMP? 60.1 F (15.6 C) INSIDE TEMP? 70 F (21.1 C) B I R D NO? 10,000 BIRD AGE? 25 INSIDE R H ? 6 0 R E L A T I V E H U M I D I T Y = 75 V E N T I L A T I O N , f t 3 / m i n 53,295 (90,126 m 3 /hr) 0600 HR TEMP? 69 F (20.6 C) INSIDE T E M P ? 7 0 F (21.1 C) BIRD N O ? 1 BIRD AGE? 15 INSIDE R H ? 5 0 WARM, HUMID; USE M A X V E N T ; R H = 9 5
Definition of terms used in program are: 1
Linearization of the nonlinear humidity-temperature relationship results in an error in dewpoint temperature that does not exceed approximately 1.2 F (.67 C) for the range of conditions indicated.
X = Minimum daily temperature dewpoint temperature, F; Y = Temperature in house, F;
= outside
1078
REECE AND LOTT
N D R Z A
= Number of birds in house; = Bird age in days; = Inside RH, %; = Inside dewpoint temperature, F; = Outside specific humidity, pounds moisture per pound dry air; B = Inside specific humidity, pounds moisture per pound dry air; W = Chicken weight, kg; V = Ventilation rate for house, ft 3 /min (m 3 /hr) In the second example given, the desired RH of 60% cannot be maintained by ventilation alone. Therefore, reiterations are performed, each with an increase of RH in 5% increments, until a solution is obtained. In this example, the resulting RH was 75%. In the third example, no solution is possible, even with RH of 95%; this is indicated by the "WARM, HUMID; USE MAX VENT; RH=95" response. The program has been used with excellent results to adjust the ventilation rate for broiler
research houses at South Central Poultry Research Laboratory. It is used daily during the brooding and growing phase to adjust the ventilation fans. Normally, it is used in the morning of each day shortly after the 0600 hr minimum daily temperature has been observed, and the adjustment made at that time is retained for the enusing 24 hr.
REFERENCES Reece, F. R, and B. D. Lott, 1982a. Heat and moisture production of broiler chickens during brooding. Poultry Sci. 61:661—666. Reece, F. N., and B. D. Lott, 1982b. Optimizing poultry house design for broiler chickens. Poultry Sci. 61:25-32. Reece, F. R, and B. D. Lott, 1982c. The effect of environmental temperature on sensible and latent heat production of broiler chickens. Poultry Sci. 61:1590-1593. Reece, F. R, and B. D. Lott, 1982d. Typical broiler chicken growth rates, 1981. Poultry Sci. 61: 1013-1014.