The volume flow rate of compressed and delivered gas at the standard discharge point is defined by the atmospheric conditions of the site and is unaffected by the compressor. F.A.D. can be expressed in liters per second (l/s), meters per minute (m3/min), or cubic feet per minute (cfm). 1 l/s = 0.264 m3/min.
The volume flow rate of air at any given point in a facility is affected by two factors: pressure difference across the element, and static pressure due to gravity. The equation for calculating the flow rate of air at a given point is Volume Flow Rate = Pressure Difference x Static Head. For example, if the pressure difference is 10 inches H2O and the static head is 12 inches, then the volume flow rate is 100 l/s.
For facilities with multiple outlets, such as supply lines to different rooms, it is important to know which outlet will receive the highest volume flow rate. This will determine which outlet should have the largest diameter pipe. For example, if one room needs more air than another room, then the person building the system should ensure that the larger pipe carries the higher volume flow rate. Otherwise, the room with less demand will not get its required amount of air.
In general, the volume flow rate of air in buildings is not much greater than 30 l/s.
When measured or estimated inside the input condition, free air delivery is the flow rate of compressor volume inside the output. The free air delivery may be measured by compressing the outside air at the compressor pressure and releasing it back into the atmosphere, i.e. the inlet condition. The volume of air so compressed is the free-air delivery. This method cannot be used if the ambient conditions are not stable (no measurable temperature difference between day and night), and it also requires a reliable means of determining when the tank is full.
An alternative method for estimating free air delivery is to measure the tank pressure and estimate the volume of air stored in the tank based on its capacity. This assumes that the vehicle was sitting for a long time with the engine off. If the engine is still running when this measurement is made, some of the air will be pulled from the tank into the engine, reducing the amount of air available for delivery.
A third method uses a manometer to estimate the volume of air in the tank. This involves attaching a manometer to the fuel tank and reading the height marked on the manometer. If no mark is placed on the manometer then assume that the tank is full and stop filling it. Free air delivery is then calculated as the product of the tank pressure and the tank's volume divided by 100.
CFM (Cubic Feet per Minute Delivered). FAD (Free Air Delivery) is the actual amount of compressed air supplied translated back to the compressor's intake conditions. It can be calculated by multiplying the CFM rating of the air pump by 7.38.
A common mistake is to think that because you have a large tank you can use more air than what's given out in one blast. This isn't true; you need to maintain an adequate supply of air for effective cleaning. If you use up all the air blowing with no replacement, your equipment will not function properly when it needs cleaning.
The amount of air used depends on many factors such as size of room, type of cleaning performed, etc. But generally 10-20% of a house's total air conditioning capacity is sufficient to clean a typical home.
You should also know that high humidity affects how much air you need. As water vapor increases in volume within a closed space, it requires more air to keep the pressure constant. This is called "head" pressure. So for example, if you were to double the humidity of a room from 30% to 60%, you would need to increase the air flow by 33%.
Free Air Delivery (FAD) is a standard measure of an air compressor's capability. FAD is the flow rate of air determined by measuring it at the compressor's outlet and defining it at the matching outlet pressure, e.g., 300 litres per minute @ 700 kPa. The higher the FAD number, the greater the capacity of the compressor.
Free air delivery determines how much air can be delivered to a given point in one minute under specified conditions. For example, if you need to fill 100 cubic meters of space with air, then the compressor should deliver 3000 liters of air per minute at normal room temperature. If the room temperature rises by 10 degrees Celsius, then the compressor needs to increase its speed to keep up with the increased demand for air.
Compressors work on the same basic principle as bicycle pumps - they compress air inside a cylinder and then release it through a nozzle attached to the outside of the pump. The amount of compression that can be achieved in a pump or compressor depends on several factors, such as size, type, and construction quality of the machine. In general, more expensive compressors can achieve higher levels of compression than cheaper models. Also, handmade machines usually have larger valves in their cylinders which allow them to handle high pressures without breaking down.