The metric equivalent of cv is kv which is defined as the amount of water that will flow in m3 hr with 1bar pressure drop. For example you might apply an environmental pressure of 16 bar at the inlet a static pressure of 15 bar at the outlet and measure the flow rate at the outlet.
When sizing a control valve the most common approach is to calculate the flow coefficient cv which is a measure of the capacity of the valve body and trim.
Cv valve unit of measure. So to model this in flow simulation simply define the pressure drop across the valve with explicit inlet and outlet pressure conditions and measure the flow rate. Mathematically the valve coefficient cv or flow capacity rating of valve can be expressed as. Assembling data all units must correspond to those shown on the nomograph.
It is a unit of measure for comparing valve flows. For butterfly and eccentric disk rotary valves use the liquid flow rate q scale designated for double ported valves. In more practical terms the flow coefficient c v is the volume in us gallons of water at 60 f that will flow per minute through a valve with a pressure drop of 1 psi across the valve.
The valve coefficient also known as flow coefficient of a valve is a relative measure of its efficiency at allowing fluid flow. The valve coefficient cv in imperial unit the number of us gallon per minute of water at 60 f that will flow through a valve at specific opening with a pressure drop of 1 psi across the valve. It describes the relationship between the pressure drop across the valve and the corresponding flow rate.
For measuring the valve capacity of control valves the coefficient cv or its metric equivalent kv is adopted. For liquids the flow coefficient cv is expressed with water flow capacity in gallons per minute gpm of 60of with pressure drop 1 psi lb in2. For high recovery ball type valves use the liquid flow rate q scale designated for single ported valves.
δp 5 kg cm 2. So cv 1 17 50 x sqrt 0 943 5. See valve flow coefficient cv.
Q is the rate of flow. The valve flow coefficient cv is the number of u s. Inlet pressure 32 kgf cm2 convert to absolute pressure 33 03 kgf cm2 a.
A valve cv can be described as the number of gallons per minute gpm at 60 o f 15 5 o c that will pass through a valve with an associated pressure drop of 1 psi. Gallons per minute of water at 60 f that will flow through a control valve at a specified opening when a pressure differential of 1psi is applied across the valve. G l 943 kg m 3 convert to unit water 1 0 943.
Flow expressed by volume cv q sg dp 1 2 1. Cv 25 4 example 2. Flow rate 48 000 sm3 hr.
The definition of cv factor is the number of gpm gallons per minute that will pass through a control valve with a pressure drop of one 1 psi. What is cv valve flow coefficient. 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.