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At least one author takes a different approach in order to avoid a need for the expression freestream static pressure. Gracey has written "The static pressure is the atmospheric pressure at the flight level of the aircraft". [15] [16] Gracey then refers to the air pressure at any point close to the aircraft as the local static pressure.
A diffuser is "a device for reducing the velocity and increasing the static pressure of a fluid passing through a system”. [1] The fluid's static pressure rise as it passes through a duct is commonly referred to as pressure recovery. In contrast, a nozzle is used to increase the discharge velocity and lower the pressure of a fluid passing ...
The fan maintains a constant static pressure in the discharge duct regardless of the position of the VAV box. Therefore, as the box closes, the fan slows down or restricts the amount of air going into the supply duct. As the box opens, the fan speeds up and allows more air flow into the duct, maintaining a constant static pressure. [11]
HVAC (heating, ventilation, and air conditioning) is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many ...
The airtightness of a building is often expressed in terms of the leakage airflow rate through the building's envelope at a given reference pressure (usually 50 pascal) [10] divided by the: Heated building volume V. At 50·Pa, it is called the air change rate at 50 Pa and usually noted n 50 (units: h −1). [13] [14] Envelope area A E.
Rooftop HVAC unit with view of fresh-air intake vent Ventilation duct with outlet diffuser vent. These are installed throughout a building to move air in or out of rooms. In the middle is a damper to open and close the vent to allow more or less air to enter the space. The control circuit in a household HVAC installation.
The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N·m −2 or kg·m −1 ·s −2). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N·m −2. When indicated, the zero reference is stated in parentheses following the unit, for example 101 kPa (abs).
Differences in static pressure arise from global and microclimate thermal phenomena and create the air flow we call wind. Dynamic pressure is the pressure exerted when the wind comes into contact with an object such as a hill or a building and it is described by the following equation: [ 2 ]