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Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.
To calculate the density of air as a function of altitude, one requires additional parameters. For the troposphere, the lowest part (~10 km) of the atmosphere, they are listed below, along with their values according to the International Standard Atmosphere , using for calculation the universal gas constant instead of the air specific constant:
Standard cubic feet per minute (SCFM) is the molar flow rate of a gas expressed as a volumetric flow at a "standardized" temperature and pressure thus representing a fixed number of moles of gas regardless of composition and actual flow conditions. It is related to the mass flow rate of the gas by a multiplicative constant which depends only on ...
Stowage factor. In shipping, the stowage factor indicates how many cubic metres of space one tonne (or cubic feet of space one long ton) of a particular type of cargo occupies in a hold of a cargo ship. [1] It is calculated as the ratio of the stowage space required under normal conditions, including the stowage losses caused by the means of ...
The IEEE symbol for the cubic foot per second is ft 3 /s. [1] The following other abbreviations are also sometimes used: ft 3 /sec; cu ft/s; cfs or CFS; cusec; second-feet; The flow or discharge of rivers, i.e., the volume of water passing a location per unit of time, is commonly expressed in units of cubic feet per second or cubic metres per second.
A standard cubic foot (scf) is a unit representing the amount of gas (such as natural gas) contained in a volume of one cubic foot at reference temperature and pressure conditions. It is the unit commonly used when following the customary system, a collection of standards set by the National Institute of Standards and Technology.
The acre-foot is a non- SI unit of volume equal to about 1,233 m 3 commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water, [1] and river flows. An acre-foot equals approximately an eight-lane swimming pool, 82 ft (25 m) long, 52 ft (16 m) wide ...
Terminal velocity. The downward force of gravity (Fg) equals the restraining force of drag (Fd) plus the buoyancy. The net force on the object is zero, and the result is that the velocity of the object remains constant. Terminal velocity is the maximum speed attainable by an object as it falls through a fluid (air is the most common example).