What is the discharge coefficient of an orifice?
What is the discharge coefficient of an orifice?
The discharge coefficient is a dimensionless number used to characterise the flow and pressure loss behaviour of nozzles and orifices in fluid systems. Orifices and nozzles are typically used to deliberately reduce pressure, restrict flow or to measure flow rate.
How do you calculate orifice discharge coefficient?
The discharge coefficient of an orifice or nozzle is defined as the ratio of the actual to theoretical flow rate:
- Cd=Measured Flow RateTheoretical Flow Rate (1)
- η=σΔp12ρ¯V2 (6)
- ξ=σΔp¯Δp (7)
What is CV in orifice meter?
Cc = Area of vena contracta/ area of orifice. Cv = actual velocity at vena contracta/theoretical velocity.
Why is the coefficient of discharge less than 1 orifice?
This is the reason why orifice meters are less accurate than venturi meters. Beyond the vena contracta point, the fluid expands again and velocity decreases as pressure increases. Losses in orificemeter are more as there is no convergent and divergent cones and therefore coefficient of discharge is less.
How do you calculate flow coefficient?
The equation for calculating the valve flow coefficient is Cv = Q √ (SQ/P).
What is the usual limit of the coefficient of discharge?
The range for coefficient of discharge (Cd) for a venturimeter is. 0.61 to 0.79. 0.72 to 0.89.
Why discharge coefficient is high in Venturi meter than orifice meter?
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 …
How do you calculate CV value?
The formula for the coefficient of variation is: Coefficient of Variation = (Standard Deviation / Mean) * 100. In symbols: CV = (SD/x̄) * 100. Multiplying the coefficient by 100 is an optional step to get a percentage, as opposed to a decimal.
What is the difference between coefficient of discharge and coefficient of velocity?
The ratio of the actual velocity of the jet, at vena-contracta, to the theoretical velocity is known as the coefficient of velocity. Coefficient of discharge (Cd): The ratio of an actual discharge through an orifice to the theoretical discharge is known as the coefficient of discharge. Coefficient of contraction (Cc):
Can a discharge coefficient be greater than 1?
In practice, the discharge coefficient cannot be greater than one. This is a fact. The error may be in compensating the values of the variables in the equation. Verifies units, values, and homogeneity of area values.
Why is the coefficient of discharge greater than 1?
In HEC-RAS the factor attached to the head loss through a culvert or bridge includes both the entrance and exit losses. In fact, the usual assumption is that the outlet loss is equal to the velocity head. This is why you get a factor greater than 1.
What is a good CV value?
CVs of 5% or less generally give us a feeling of good method performance, whereas CVs of 10% and higher sound bad. However, you should look carefully at the mean value before judging a CV. At very low concentrations, the CV may be high and at high concentrations the CV may be low.
What are the typical values for discharge coefficient?
Typical Values for Discharge Coefficient C_ {d} C d Equipment Type β beta β min β beta β max C d C_ {d} C d Orifice Plate, thin sharp edged – – 0.61 Venturi Nozzle, Machined 0.4 0.75 0.995 Venturi Nozzle, Rough Welded Sheet Metal 0.4 0.70 0.985 Venturi Nozzle, Rough Cast 0.3 0.77 0.984
What are orifices and nozzles used for?
Orifices and nozzles are typically used to deliberately reduce pressure, restrict flow or to measure flow rate. This article gives typical values of the discharge coefficient for common orifice and nozzle designs.
What is the contraction coefficient of flow through an orifice?
Flow Through an Orifice. This follows because the region where the lines of flow are converging on the orifice is far removed from the walls, and the velocity of the fluid in contact with the walls is negligible. Thus, the contraction coefficient is exactly . This arrangement is known as a Borda mouthpiece, after Jean-Charles Borda (1733-1799).
How does fluid flow through an orifice?
Flow Through an Orifice. Let be the hydrostatic pressure at the level of the orifice when the orifice is closed. Here, is atmospheric pressure. The fluid experiences a thrust from the section of the wall directly opposite the orifice, and a thrust from the section of the wall closing the orifice.
