What are Applications of Circular orifice?

Answer 1

An orifice plate is a device used to measure the rate of fluid flow. It uses the same principle as a venture nozzle namely Bernoulli’s principle which says that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa.

An orifice plate is basically a thin plate with a hole In the middle. It is usualy placed in a pipe in which fluid flows. As fluid flows through the pipe, It has K.a certain velocity an a certain pressure. When the fluid reaches the orifice plate, with the hole in the middle of the fluid is forced to converge to go through the small hole, the point of maximum converyence actually occurs shortly downstream of the physical orifice, at the so called vena contracta point as it does so the velocity and the pressure changes. Beyond the vena contracta the fluid expands and the velocity and pressure change once again. By measuring the difference in fluid pressure, between the normal pipe section and at the vena contracta, the volume metric and mass flow rates can be obtained from Bernoulli’s equation.

By assuming steady-state, compressible, laminar flow in a horizontal pipe negligible frictional losses, Bernoulli’s equation reduces to an equation relating the conversation of energy at two points in the fluid flow or V1=Q/A1 & V2=Q/A2.

Slowing for Q and introducing the beta factor β=d2/d1 as well as coefficient of the discharge Cd.

And finally introducing the expansion γ to account the compressibility of gasses and the meter coefficient C which is defind as to obtain the final equation for the volumetric flow of the fluid upstream of the orifice.

It we consider about the value of coefficient of velocity (Cv). It may be accurated due to the practical errors. In that case we had to control the over flow rate actually. The top level of a adjustable over flow pipe was decreased gradually. So we had to hold it during the experiment to make the head constant. There may be some errors in measuring time, also we calculated to value of the Q using the equation Q=V/t, the Q2=V2/t2. If there is any error in time. If will increase when “t” become “t2”. So then there may be errors in values of Cd of the first part of experiment.

In practically orifice is used in channels, pipelines, canal or hydro power stations to act as a water controller. Mostly those orifice are used to in reservoirs and pipelines. It may be used for measuring the rate of flow out of the reservoirs or through a pipelines, orifice may be in the wall or in bottom of the reservoir or tank .

The orifice equation describes the rate of flow of liquid through an orifice.

The equation can be represented as:

Q = Cd A\sqrt{2gh}

where Q = flow (cubic metres per second)

C(d) = coefficient of discharge

A = area of orifice (square metres)

g = acceleration from gravity (9.81 m/s)

h = head acting on the centreline (m)

For a circular orifice, the equation becomes:

Q = Cd (1/4 \pi D^2)\sqrt{2gh}

Typical values for the coefficient of discharge are:

Sharp orifice: 0.62

Tube: 0.80