Negative Pressure Ventilation and Inlet Winch Motor System
In recent years, negative pressure ventilation specialists have been recommending not only the size of the inlets but also their number. Two decades ago, a 120-meter-wide hall might have required 10 or 20 inlets measuring 10 x 120 cm (totaling 1.2 square meters). Today, many advanced halls have more than 50 inlets. The dramatic increase in the number and size of inlets in today’s halls allows breeders to better control temperature, air quality, and fuel consumption. The better a breeder can control these factors, the more profitable they can be.
Number of required inlet winch motors
10 small inlets can only accommodate a maximum of 2 to 4 100 fans, which depends on the degree of sealing of the hall, so it can be easily seen that there will not be enough to enter the hall for more than 4 roosters. Small inlets can be sufficient to provide minimum ventilation in cold conditions, but since it is not possible to provide ventilation in not very cold and warm conditions with a small number of inlets, a small number of inlets is not recommended. For example, a poultry farm that wants to ventilate its hall with several 100 fans in relatively cold weather (10 degrees Celsius), due to the insufficient number of inlets, has to open some of the tunnel ventilation windows (summer). This action causes cold air to fall to the floor of the hall and become caked.
Also, in the conditions of the poultry farmer, he has to be constantly aware of the farm conditions so that whenever the outside air becomes warm enough to fully open the tunnel ventilation window (summer), he does so, otherwise the quality of the air in the house and consequently its performance will be affected. In advanced halls with tunnel ventilation (summer), the number and size of fans have increased significantly. Although it seems that these fans are used only for ventilation in summer conditions, if the number of inlets is sufficient, these fans can be easily used for ventilation in winter conditions and mountainous climates in spring and autumn.
Tunnel ventilation fans (summer) and wall inlets allow the poultry farmer to increase the ventilation of his house more than expected whenever he wants. With a sufficient number of wall inlets, the poultry farmer can use 2 or 3 100 fans to 7 140 fans. Also, if he wishes, he can ventilate the houses through the inlets even in not very hot weather. The key point in being able to implement this flexible program is that the house must be equipped with a large number of adjustable wall inlets. Houses that are equipped with a large number of vane fans face only one problem, and that is the amount of opening of the inlets in proportion to the fans being turned on and off.
The opening size of the inlets for 2 100 fans may open the inlets slightly. If for 4 fans of 100 the inlets must be opened twice as much, basically the more the number of fans on, the more the inlets will be open. To get rid of the manual and continuous adjustment of the inlets, many poultry farmers install a manual or electric winch system. The warmer the outside air, the more fans will be on and the winch system will open the inlets more, and vice versa. This adjustment was determined based on the amount of negative pressure in the house or the amount of vacuum that the fans create. An inlet winch system should be able to maintain negative pressure in the house in the static pressure range of 12 to 25 Pascals for any number of fans on.
If this fan is turned on and the static pressure exceeds 25 Pascals, the winch system must open the inlets. If the static pressure drops below 12 Pascals due to a fan being turned off, the winch system closes the inlets to the extent that the static pressure returns to the desired range. If all fans are turned off, the winch system closes the inlets completely. In spring and autumn, when temperatures may reach 0 degrees Celsius at night and 24 degrees Celsius during the day, proper ventilation is a major challenge that can justify the use of the winch system. In this situation, 2 100 fans at night may change to 4 100 fans during the day. In this situation, the winch system variable can change the degree of openness of the inlets according to changes in the number of fans so that optimal ventilation conditions are always maintained.
What is negative pressure?
In simple terms, consider a poultry house with an entrance door and a fan. The hinged door, when normally open when the fan is off, remains open because the air pressure inside and outside the house is equal. As soon as you turn on the fan, the door of the house suddenly closes. In fact, by turning on the fan and discharging the air from the house to the outside, it creates a pressure difference between the inside and outside of the house, which causes a wind flow and closes the entrance door of the house.
The importance of adjusting and recording negative pressure in poultry houses
In houses with inlets, the air flow speed in the section of the valves is of great importance, and the factor that causes this speed is always negative pressure. As the negative pressure of the house increases, the speed in the entrance section increases, and as the negative pressure decreases, the speed in the entrance section decreases. Therefore, by maintaining this air flow speed, each house needs to stabilize the negative pressure. To better explain the issue, let’s give an example:
A certain volume of water comes out of a hose at a low speed. To increase the speed of water outflow, we must either reduce the cross-sectional area of the hose or increase the volume of water outlet by opening the tap. The same situation applies in the hall, that is, if we want to increase the air speed in the cross-sectional area of the valves, we must reduce the number of fans by keeping the number of fans constant, or increase the number of fans by keeping the number of fans open. Therefore, to maintain a constant negative pressure in the hall, the opening rate of the valves must always be proportional to the number of fans in operation.
It is important that the fresh air entering the hall must move at a standard speed according to the width of the hall and to the crown of the hall (middle of the hall), where it can mix with the warm air inside the hall and adjust its temperature, and with it, direct the warm and light air in the ceiling of the hall to the level of the flock.
So, if the vents are open more than necessary, the air flow speed in the vents does not reach the middle of the house and moves downwards in some cases, causing the chickens close to the side walls to catch cold and preventing the transfer of warm air under the ceiling to the surface. Also, if the vents are open less than necessary, the air flow speed in the vents increases and the air quickly reaches the middle of the house and, when it collides with the air that enters the house from the opposite vent, it comes to the surface of the flock. The cold air outside does not have enough time to mix with the warm air under the ceiling and adjust the temperature, causing cold stress in the middle of the house.
