(1) The branch of physics dealing with the motion and action of water and other liquids is termed hydrodynamics. Various forces act on a liquid, causing it to be in a state of motion. The dynamic head of water is an equivalent or virtual head of water in motion which represents the resultant pressure necessary to force the water from a given point to a given height and to overcome all frictional resistance. The dynamic head causing flow of a liquids is divided into three parts: velocity head, entry head, friction head.
(2) The dynamic lift of water is an equivalent or virtual lift of water in motion which represents the resultant pressure necessary to lift the water from a given point to a given height and to overcome all frictional resistance. The practical limit of actual lift in pump operation ranges from 20 to 25 feet, when the water is warm, the height to which it can be lifted decreases due to increased vapor pressure.
(3) The term total column means head plus lift. The static total column is the static lift plus the static head. The height or distance from the level of supply to the level in the tank, in feet, is termed the static total column. The dynamic total column is the dynamic lift plus the dynamic head, or the equivalent total column of water in motion. It represents the pressure resulting from the static total column the resistance to flow caused by friction.
(4) Friction of water in pipes results in loss of pressure and reduced volume of water per minute delivered. Also, friction in the faucets, in the fittings, and in the flow through the meter must be considered.
Реферат опубликован: 6/08/2007