How to Design Ventilation System for A Poultry Farmhouse

The ventilation fans for poultry farmhouses can be generally divided into two types, namely mechanical ventilation fan and natural ventilation fan. In design, it is quite necessary to pay attention to the thorough ventilation. The required ventilation volume should be calculated based on the standard ventilation volume of each chicken and the number of the chicken, and then the number of fans to be installed is calculated according to their performance.

The windows should be placed symmetrically and evenly to ensure thorough ventilation in the poultry house. Meanwhile, open or close some windows according to the ventilation requirements to take advantage of both natural wind force and the ventilation effect of temperature difference.

Mechanical ventilation is the main method to regulate the internal environment conditions in case of a closed poultry house, high density of broilers, and breeding in large flocks. Ventilation is closely related to temperature control, humidity control, dust removal, and air composition adjustment.

Mechanical ventilation fans are divided into positive pressure ventilation fan and negative pressure ventilation fan:

Positive pressure ventilation:

Positive pressure ventilation means bringing in the fresh air from the outside into the poultry house through a fan to generate positive pressure and then discharge the turbid air through a vent on the other side. This method is generally used in winter when heaters are used for heating, otherwise, the positive pressure ventilation fans are not used.

Negative pressure ventilation:

Negative pressure ventilation is commonly used in almost all modern poultry houses in the current breeding industry. The fan is installed on one wall of the poultry house, and an air inlet is set on other walls. The fresh air flows in from the air inlet, passes through the poultry house and the polluted air is discharged by the fan. The ventilation principle is that the air pressure in the poultry house gets slightly lower than the outside when the negative pressure exhaust fan is turned on, and the fresh air outside the poultry house automatically flows in under the influence of the negative pressure.

There are several ways of negative pressure ventilation are commonly used in farm cooling: cross ventilation, transition ventilation, longitudinal ventilation, and tunnel ventilation:

1. Cross ventilation
   Cross ventilation mainly has two kinds of design, respectively positive pressure system, and negative pressure system. Although it can adjust the temperature, improve the air distribution, and reduce the air intake in the poultry house, positive pressure system is rarely used in production practice due to its disadvantages of high equipment cost, high consumption, difficult installation, and narrow scope of application.Negative pressure ventilation system with various ways of design and installation is widely used, and horizontal installation ventilation is the one that is usually adopted.The negative pressure exhaust fan is installed horizontally to ventilate and lower the temperature, and cross ventilation should be used when the poultry house is short in length and the span is no more than 10 meters. To put it simple, the installation position of the negative pressure fan should be fixed on a strong solid wall on one side of the poultry house, and an air inlet should be set at the corresponding place on the wall opposite to the negative pressure exhaust fan. The fresh air flows in from the air inlet, then passes through the poultry house thoroughly, and finally it is discharged. The installation position design of the negative pressure exhaust fan requires that the exhaust air volume is slightly larger than the intake air volume, so that the air pressure in the poultry house is slightly lower than that in the outside, which is helpful for the fresh air outside the poultry house to automatically flow in under the influence of the negative pressure.
2. SideVentilation   The negative pressure exhaust fan at the end of the poultry house ventilates, and the small air inlet on the sidewall takes in air. The purpose is to ventilate as much as possible under the premise of heat preservation to ensure the fresh air in the poultry house, and it is generally used for broilers 3 weeks and up, or in spring and autumn. The negative pressure in the poultry house is mostly 10-20Pa.
3. Longitudinal ventilationThe negative pressure exhaust fan is installed longitudinally for ventilation and climate control. For the poultry house with a length of more than 80 meters and a span of more than 10 meters, the installation position of the negative pressure exhaust fan should be longitudinal installation. Longitudinal installation of the negative pressure fan on the poultry farm means that the negative pressure exhaust fan is installed on the gable on one side of the poultry house, and the air inlet is set on the opposite wall or either wall next to the opposite wall, so that the fresh air can pass through the longitudinal diameter of the poultry house and be discharged under the influence of the negative pressure, and it can also be interpreted as the negative pressure fan is installed on one wall of the poultry house, and the air inlet can be correspondingly set on any of the other three walls, which not only optimizes the rationality of the ventilation design of the poultry house, reduces the installation cost, but also achieves a quite ideal ventilation effect. In the summer, evaporative cooling pads are usually installed at the air inlet to effectively cool the poultry house down, that is, evaporative cooling. It is generally used in summer with high temperature and humidity, and the negative pressure in the poultry house is mostly 20-30Pa. The longitudinal ventilation system of poultry houses has been widely used in the contemporary poultry industry due to its advantages of simple design and installation, low cost, good ventilation, and cooling effects, etc.
4. CombiTunnelVentilation      The ventilation tunnel crosses the poultry house or leads to the middle of the poultry house, on which roof ventilation fans are installed. When the fan is turned on, air enters from the evaporative cooling pad or window of the duct and exits from the negative pressure exhaust fans and the rooftop ventilation fans. This method is the best ventilation method in the cold season and early stage of breeding.

How to calculate the number of fans needed for a poultry house?

Side Ventilation Fans:

A poultry house is usually equipped with a side fan (small fan) for the fundamental purpose of maintaining the minimum ventilation volume in it.

The number of side fans = the minimum ventilation volume at the maximum weight of the flock in the poultry house ÷ the ventilation volume of the fan

For example, to build a poultry house holding 30,000 chickens, if the maximum average weight of each is 3 kg, then the number of side fans = 30,000 × 3 kg/each  × 0.0155 cubic meters/minute. kg (minimum ventilation coefficient) ÷ the ventilation volume of the fan

Taking into account the fan volume losses caused by various reasons, therefore, 1-2 more fans must be installed in actual practice.

Longitudinal Ventilation Fans

The number of longitudinal fans to be installed is related to the high temperature in summer. In hot summer, the air cooling effect can be achieved by increasing the wind speed in the poultry house, thereby reducing the sensible temperature of the flock.

The number of longitudinal fans = the cross-sectional area of the poultry house × the desired wind speed ÷ the ventilation volume of the fan (due to regional differences, the temperature and humidity in summer in each region are different, so the desired wind speed varies as well)

For example, if the poultry house is 100 meters long, 14 meters wide, and the sidewall is 2.5 meters high, the roof is 4 meters high, and the desired wind speed is 2.5 meters per second, then the number of longitudinal fans = 14 meters × {2.5 meters + (4 meters- 2.5 meters) ÷ 2} × 2.5 meters/second × 60 seconds/minute ÷ ventilation volume of the fan

Similarly, taking into account the fan volume losses caused by various reasons. Therefore, 1-2 more fans must be installed in actual practice.

In modern and large-scale breeding industry, fans play an extremely important role in the entire breeding process. Therefore, the number of ventilation fans to be installed must be calculated accurately, or have more as spare. As for the position and mode of installation, it should be accordingly determined based on different regions and ventilation modes. The methods used may vary, but the principle is the same.