Ventilation is probably one of the most difficult parameters to manage in agricultural buildings. It requires a grower’s constant attention: over or under ventilating can make the difference between a grower’s profit and loss.
During the hot season, heat rising is the major concern. If it is not removed, environment temperature will rise with negative consequences. The purpose of ventilation during the cold season is very different: the goal is to bring enough fresh air to prevent the growth of moisture/humidity while at the same time keeping the heat produced by the heaters.
Since the goal of ventilation changes throughout the year, the way we ventilate a house also needs to change.
Positive pressure system and Negative pressure system
There are basically two different fans that can be used to ventilate an environment: pushing air in or taking air out. When a fan blows air into a house, it is referred to as a positive pressure system. When air is exhausted by fans, it is referred to as a negative pressure system.
By far, the most popular method of fan ventilation is under negative pressure for its easy management and smartness.
In a negative pressure ventilation system, the fan sucks a certain amount of air from the building. Consequently, in the house occurs a pressure lowering through which it is possible to obtain a vacuum effect of clean air thanks to the air inlet systems that uniformly supply fresh air. The static pressure value (measured in Pascal) depends on the type of crop and/or breeding, but generally, we take as reference the average value of static pressure at 25Pa.
In order to do a right comparison among different models, it is important to be able to read the right data: for an exhaust fan the performance data (air flow or efficiency or power absorption) at 0Pa (0”) are totally insignificant because in any case, in a negative pressure system, the fan will work in that condition. Otherwise, it is very important to analyze the behavior of the performance parameters to growing of the negative pressure value because they represent the behavior of the device in the real application.
Seeing the data reported in the table, you can understand how the negative pressure value can influence the fan performance.
Following a transparency philosophy with its customers, Pericoli Group decided to highlight the actual performance of exhaust fans under real working condition in its brochures.