Pressure

Date: 2015-10-07; view: 461.

1) Condition that exists when more air is supplied to a space than is exhausted, so the air pressure within that space is greater than that in surrounding areas. Under this condition, if an opening exists, air will flow from the positively pressurized space into surrounding areas.

2) It is a term used to characterize the reduction in air pressure between any two points in the ventilation duct network. It occurs as the compressed air travels through filters and ducts. In airflow system, the energy is measured as "pressure drop."

3) The total pressure measured in relation to a perfect vacuum. The sum of atmospheric and gauge pressures.

4) Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas. Under this condition, if an opening exists, air will flow from surrounding areas into the negatively pressurized space.

5) The force exerted by the weight of the atmosphere on a given area. It is measured in units of pascals (Pa) or torr (millimetres of mercury). The normal atmospheric pressure is 760 torr or 101 kilopascals (kPa).

6) Instruments used to measure pressure are called pressure gauges. Generally it gives air pressure relative to atmospheric pressure. It can show a negative pressure (less than atmosphere), or positive (greater than atmosphere.)

7) In flowing air, the total pressure minus velocity pressure. The portion of the pressure that pushes equally in all directions.

8) In flowing air, the sum of the static pressure and the velocity pressure.