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# What is Static Pressure?

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• Edited By: Heather Bailey
2003-2018
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Static pressure is the pressure that is exerted by a liquid or gas, such as water or air. Specifically, it is the pressure measured when the liquid or gas is still, or at rest. Several different industrial and scientific applications exist for this term, but most have to do with air pressure rather than water pressure. In aviation, for example, a static pressure system is how a plane's altimeter and airspeed indicator operate. In construction, it refers to the pressure that a fan must exert in a ventilation system in order to cause air to flow.

The concept is also an essential one in the science of fluid mechanics. Scientifically, static is distinguished from dynamic pressure, both of which are components of a system's total pressure. This relationship is defined in Bernoulli's equation, and relates to the study of the flow and motion of fluids. The principle of Bernoulli's equation is that static pressure and dynamic pressure may vary greatly in different areas of a fluid in motion, but the total pressure remains constant.

One of the more important areas where an accurate understanding of this type of pressure is important is in the field of aviation. The goal of a plane's altimeter is to measure the air pressure at the height at which it is flying, to determine the altitude. The way this is done is through a small opening in the outside of the aircraft, called the static port.

Unfortunately, no matter where the static port is placed, it will always read an air pressure that is at least slightly different from the local static air pressure at that altitude. This is true whenever the plane is in motion in the air. To attempt to overcome this error, the static port must be placed very carefully by the designer of the aircraft. A well-placed static port will minimize the discrepancy, known as the position error.

In architecture and construction, static pressure refers to a structure's ventilation system, and the way in which the system's components and ductwork resist airflow. It is important to know what this pressure is, because the fan that circulates air through the system must be able to do so effectively. The fan must be strong enough to overcome the resistance exerted by the ventilation system, and to push air through it. In general, the larger and more complicated a ventilation system is, the higher its static pressure.

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 anon278700 Post 6 The restriction of air flow in the air duct system is going to determine the static pressure? anon179346 Post 4 @ 3" static what gauge metal do i need? anon172402 Post 3 How much pressure is inside a paraglider wing?Is ram air a myth? --Simon Amphibious54 Post 2 HVAC professionals also use static pressure to determine the type of pump necessary for geothermal HVAC systems. It is important to know the static pressure in these HVAC systems because they circulate fluids underground to heat and cool a home. Static pressure is also measured at the vents to determine the flow of air coming from your HVAC system. Understanding static pressure, negative static pressure, and flow rates is important in the HVAC industry. GiraffeEars Post 1 Static pressure measurements are used in plumbing and irrigation systems too. Static pressure is the measure of a fluid at rest, and determining static pressure is important in determining dynamic pressure (the pressure of a fluid in motion). Friction and elevation affect the dynamic pressure of a fluid system. An irrigation system that travels uphill will lose pressure for every foot of elevation. Conversely, an irrigation system that flows downhill will increase dynamic pressure. Most water systems are designed to work best when dynamic pressure is at optimal levels. A water system may need pumps to increase pressure, while a water system with too much pressure may need to increase friction. A plumber or irrigation specialist that understands these concepts will ensure your shower has good pressure, or your sprinkler system waters your entire lawn.