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A simplified version of the definition is: The k v factor of a valve indicates "The water flow in m 3 /h, at a pressure drop across the valve of 1 kgf/cm 2 when the valve is completely open. The complete definition also says that the flow medium must have a density of 1000 kg/m 3 and a kinematic viscosity of 10 −6 m 2 /s, e.g. water. [clarify]
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.
Control valves can also work with hydraulic actuators (also known as hydraulic pilots). These types of valves are also known as automatic control valves. The hydraulic actuators respond to changes of pressure or flow and will open/close the valve. Automatic control valves do not require an external power source, meaning that the fluid pressure ...
All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the mass flow sensor and adjusts the proportional valve ...
The effects a variable flow system had on the selection of control valves, was not initially realized. A control valve was selected by using the same K v calculation, and the bypass on a 3-port valve blocked, giving a 2-port valve. It was not that simple. This is because our K v calculation K v = flow rate [m 3 /h] / ΔP [bar
[4] [5] [6] A generalized model of the flow distribution in channel networks of planar fuel cells. [6] Similar to Ohm's law, the pressure drop is assumed to be proportional to the flow rates. The relationship of pressure drop, flow rate and flow resistance is described as Q 2 = ∆P/R. f = 64/Re for laminar flow where Re is the Reynolds number.
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Simple hydraulic control valves are binary, they are either on or off. Servo valves are different in that they can continuously vary the flow they supply from zero up to their rated maximum flow, or until the output pressure reaches the supplied pressure. More complex servo valves can control other parameters.