This is so due to the effect of surface tension and friction from the external fluid. It is more likely reliable to measure the coefficient of discharge with a constant head rather than a falling head. With a constant flow, yielding a constant head, measurement could be done more accurately since variables are less. Such produces a less probability of committing errors in measurement. However with a decreasing head, the experimenters also have to measure the time elapsed that took the head from its initial to a final height.
No doubt, it is more difficult to attain an accurate final answer for Cd since the error might have piled from every step of the computation. Conclusion The thickness of the wall is assumed small compared to the diameter of the orifice. Because of the convergence of the streamlines approaching the orifice, the cross section of the jet decreases slightly until the pressure is equalized over the cross-section, and the velocity profile is nearly rectangular.
This point of minimum area is called the vena contracta. These two standards can be used to derive the relationship between the Flow Coefficient C v and the Discharge Coefficient C d for relief valves.
There are minor differences in the nomenclature used in each standard, so for the purpose of this article, the nomenclature will be defined for the equations below along with the engineering units being used. When sizing a control valve, the minimum required flow coefficient is calculated based on the design flow rate and expected pressure drop across the valve, and a valve is selected that has a flow coefficient greater than the calculated value.
There are other factors that may be included in the sizing equation to account for piping geometry, high viscosity, or choked flow conditions. Using U. When sizing a relief valve, the minimum required effective area is calculated and a relief valve is selected that has an effective area greater than the calculated value. The sizing equation for relief valves for liquids using U. The right hand side of Equation 5 is common with the flow coefficient equation, Equation 2 above.
Depth times Width gives the cross-sectional area. The shape of the channel is important because of the reduction in velocity due to friction along the channel margins. The discharge coefficient — cd — varies considerably with changes in area ratio and the Reynolds number.
For an area ratio of 0. In Venturi meter losses are less so coefficient of discharge is higher whereas in orifice meter due to no convergent and divergent cones there are more losses and hence its coefficient of discharge is less. In venturi meter losses are low due to steamline shape of the diffuser and the pressure gradient is not abrupt as ….
The discharge coefficient of a Venturi meter is typically 0. Orifice meter: is a device used for measuring the rate of flow of a fluid flowing through a pipe. It is a cheaper device as compared to venturimeter. This also work on the same principle as that of venturimeter. It consists of flat circular plate which has a circular hole, in concentric with the pipe.
As you can see in the diagram there is a pipe in which fluid is passing from one side to another side that is an inlet to outlet. The manometer is attached hereto measure the pressure differences between two-point.
What is the significance of discharge coefficient? Why coefficient of discharge is always less than 1? What is the range of coefficient of discharge? What is the range of coefficient of velocity? What is the formula of coefficient of velocity? How do you find the coefficient of discharge? Which of the following has highest coefficient of discharge? What is CV in fluid mechanics?
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