Calculation Method Of Ventilation System For Broiler Cage Farming

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2024-03-22

In recent years, the rearing of broiler chickens has gradually shifted from traditional free-range methods to highly intensive cage rearing. It result in improved production performance and economic benefits. In high-density layer cage chicken farms, where mechanization and automation are high. It is essential that the ventilation and cooling facilities meet the growth requirements of broiler cage farming. The rational configuration of water curtain cooling and fan ventilation has become an urgent issue. Livi Machinery provides a reference solution.

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I. Overview of Ventilation

Ventilation Method

The most commonly used ventilation method is longitudinal ventilation, which is a negative pressure mechanical ventilation system that utilizes air convection principles to increase the comfort of the chickens. The system seals both sides of the chicken house to prevent air from entering. A high-power exhaust fan is installed at one end of the broiler cage farming house, and an inlet is set at the opposite end. It form a corridor-like structure to allow air to pass over the chicken flock.

Ventilation Volume of Fans

The ventilation volume of fans is the product of the wind speed and the cross-sectional area of the air duct.
Formula: Q = S × F where Q–ventilation volume (m3/h), S–wind speed (m/s), F–cross-sectional area of the air duct (m2).

Requirements for Airspeed in Chicken Houses

The ventilation system should ensure that the minimum airspeed in the house is not less than m3/s and the maximum airspeed does not exceed m3/s.

Air Exchange Rate

The air exchange rate for cage-reared broilers should reach 20 to 60 times per hour.
Formula: n = L ÷ S where n–air exchange rate, L–length of the chicken house (m), S–wind speed (m/s).

Correction Factor (K)

In reality, due to factors such as the impossibility of completely sealing the chicken house, obstruction of cage-rearing equipment, the ventilation efficiency of wet curtains. And the decline in fan performance, a correction factor is set for ease of calculation. According to actual experience, the correction factor is set to 0.5 to 0.6.

Determination of Fan Quantity

Formula: N = V × n / Q where N–number of fans (units), V–volume of the chicken house (m3), n–air exchange rate (times/h), Q–ventilation volume of the selected fan model (m3/h). Calculate the total air volume required for the chicken house based on the air exchange rate or production requirements, and then calculate the number of fans.

Example
For illustrative purposes, consider a chicken house with a length of 100m, width of 12.5m, height of 4m, three layers of cage rearing, 30,000 broilers stocked, with an average weight of 2.5kg. And it use a fan model with a single ventilation volume of 43,500 (m3/h).

II. Calculation of Ventilation Requirements

Poultry Farming Ventilation Requirement:

The internationally accepted calculation standard is based on the requirement per unit weight of chickens. Large chickens and small chickens have different requirements, so the calculation cannot simply be based on the number of chickens. The minimum poultry farming ventilation volume required per kilogram of broiler weight is 1.0m3/h, and the maximum ventilation volume is 7.0m3/h. Typically, a commonly used fixed value for the ventilation volume required per kilogram of broiler weight is 4.0m3/h for mature broilers; with a weight of 2.5kg for mature broilers and 1.0kg for chicks. Considering theoretical calculation errors and practical factors, a magnification factor of 1.2 to 1.4 is generally applied to the final calculation result.

Calculation of Ventilation Volume:

(1) Calculation Formula: M = A × W × Mv where M–ventilation volume (m3/h), A–design stocking density of the chicken house, W–weight value (kg) (2.5kg for mature broilers, 1.0kg for chicks), Mv–ventilation volume required per kilogram of broiler weight (m3/h).

(2) Minimum Ventilation Volume: The minimum poultry farming ventilation volume = design stocking density of the chicken house × weight value (2.5kg for mature broilers, 1.0kg for chicks) × 1.0m3/h.

(3) Maximum Ventilation Volume: The maximum ventilation volume = design stocking density of the chicken house × weight value (2.5kg for mature broilers and chicks) × 7.0m3/h.

(4) Average Ventilation Volume: The average ventilation volume = design stocking density of the broiler cage farming house × weight value (2.5kg for mature broilers and 1.0kg for chicks) × 4.0m3/h.

(5) When calculating the ventilation demand, the maximum ventilation demand is taken into account. M = A × W × Mv = 30,000 × 2.5 × 7 = 525,000m3/h.

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III. Calculation of Ventilation Requirement

Ventilation Demand:

During hot seasons, air must be exchanged rapidly to reduce heat buildup. Without adequate air exchange, heat accumulates between the inlet and exhaust fans. It lead to increased levels of harmful substances such as dust, ammonia, and carbon dioxide. Generally, the ventilation system should be capable of exchanging all the air within 1 to 3 minutes. In hot climates, air exchange should be completed within 1 minute; in warm climates, within 2 minutes; and in cold climates, within 3 minutes.

Calculation of Ventilation Requirement:

The formula for ventilation volume calculation is V = L × W × H × 60 (min/h) where V–ventilation requirement (m3/h), L–length of the chicken house (m), W–width of the chicken house (m), H–height of the chicken house (m). V = L × W × H × 60 = 100 × 12.5 × 4 × 60 = 30,000 m3/h.Maximum Ventilation Requirement Calculation: Vv = A × W × Mv. Vv—maximum ventilation requirement, A–design stocking density, W–weight value (kg) (2.5kg for mature broilers, 1.0kg for chicks), Mv–ventilation volume required per kilogram of broiler weight (m3/h). Vv = A × W × Mv = 30,000 × 2.5 × 7 = 525,000m3/h.

Calculation of Wind Speed Inside the Chicken House:

S = M ÷ F ÷ 3600 (s) where S–wind speed inside the chicken house, M–ventilation volume (m3/h), F–cross-sectional area of the air duct or chicken house. F = W × H (W–width of the chicken house in meters, H–height of the broiler cage farming house in meters). The maximum ventilation speed is: S = M ÷ F ÷ 3600 = 525,000 ÷ (12.5 × 4) ÷ 3600 = 2.92m/s.

IV. Calculation of Fan Requirements

Formula: N = V1 × n ÷ Q ÷ B where N–number of fans (units), V1–site volume (m3), n–air exchange rate (times/h). Q–ventilation volume of the selected fan model (m3/h), B–correction coefficient.
Maximum number of fans N = V1 × n / Q = (12.5 × 4 × 100) × 60 ÷ 43,500 ÷ 0.6 = 11.5 units.
Minimum number of fans N = V1 × n / Q = (12.5 × 4 × 100) × 20 ÷ 43,500 ÷ 0.6 = 3.8 units.

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V. Calculation of Wet Curtain

Wet Curtain Thickness and Ventilation Speed
For a thickness of 15cm, the ventilation speed should be 1.5 to 2m per second. For a thickness of 10cm, the ventilation speed should be 1 to 1.5m per second.

Leakage Coefficient of Chicken House Walls
The leakage coefficient can be estimated based on the structure of the chicken house. It serve as a correction parameter for expanding the wet curtain and the number of fans.

Maximum Ventilation Volume Required per Unit Weight
The maximum chicken house ventilation volume required per kilogram of broiler cage forming weight is approximately 5 to 9m3/h. A higher value can be used in the southern region, a lower value in the northern region, and an average value in the central region.

Calculation of Wet Curtain Area Required for the Chicken House
C = Vv ÷ D ÷ 3600s where C–wet curtain area (m2), Vv–maximum ventilation demand (m3/h), D–ventilation speed through the wet curtain (m/s).
For example, 525,000 ÷ 1.5 to 2m ÷ 3600s = 72 to 97m2, typically taking the median value of approximately 85m2 for the wet curtain area.

These ventilation calculations are complex, but livi Machinery is a professional supplier of chicken equipment.

In addition to providing you with chicken equipment, livi Machinery will also provide you with broiler cage forming design solutions. It include the use and installation of chicken house ventilation systems.
If you want to know more, please leave us a message.

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