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The use of the flow coefficient offers a standard method of comparing valve capacities and sizing valves for specific applications that is widely accepted by industry. The general definition of the flow coefficient can be expanded into equations modeling the flow of liquids, gases and steam using the discharge coefficient.
BELIMO Holding AG, an international group of companies, is located in Hinwil, Switzerland. [3] The company develops, produces and markets actuators for controlling heating, ventilation and air conditioning systems. Actuators and control valves make up the company's core business, and it is considered a global leader in motor control for HVAC. [4]
In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge or efflux coefficient) is the ratio of the actual discharge to the ideal discharge, [1] i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. [1] This enables the direct control of flow rate and the consequential control of process quantities such as pressure , temperature , and liquid level.
In reduced bore (sometimes reduced port) ball valves, flow through the valve is one pipe size smaller than the valve's pipe size resulting in the flow area being smaller than the pipe. As the flow discharge remains constant and is equal to the area of flow (A) times velocity (V), A 1 V 1 = A 2 V 2 {\displaystyle A_{1}V_{1}=A_{2}V_{2}} the ...
To keep water hammer low, pipe-sizing charts for some applications recommend flow velocity at or below 1.5 m/s (4.9 ft/s). Fit slowly closing valves. Toilet fill valves are available in a quiet fill type that closes quietly. Non-slam check valves do not rely on fluid flow to close and will do so before the water flow reaches significant velocity.
Electrohydraulic servo valves may consist of one or more stages. A single-stage servo valve uses a torque motor to directly position a spool valve. Single-stage servo valves suffer from limitations in flow capability and stability due to torque motor power requirements.
If the fluid is a liquid, a different type of limiting condition (also known as choked flow) occurs when the venturi effect acting on the liquid flow through the restriction causes a decrease of the liquid pressure beyond the restriction to below that of the liquid's vapor pressure at the prevailing liquid temperature.