FINAL INDEPENDENT PROJECT - CFD - Optimization of Venturimeter Geometry for Minimum Pressure Drop Using CFD Analysis
ABSTRACT
A Venturimeter is basically a differential pressure type flow meter which is used to measure the volumetric flow rate of fluids. Certain amount of pressure drop occurs in pipeline due to the reduction in flow passage in these types of flow meters. For designing flow meters, minimum pressure drop is a required condition. This pressure drop depends on various geometrical parameters of flow meters and properties of the fluid. In the present work, Computational Fluid Dynamics (CFD) has been used to investigate the effect of different geometrical parameters like convergent cone angle, divergent cone angle, diameter ratio and throat length on pressure drop in Venturimeter. Effect of each parameter has been checked by varying one parameter and keeping three parameters constant at a time. From simulation results, it was found that pressure drop fluctuates with increase in convergent cone angle, divergent cone angle and throat length while reduces with increase in diameter ratio.
Keywords: Venturimeter, CFD, Convergent Angle, Diameter Ratio, Divergent Angle, Pressure Drop
Definition of Venturimeter:
A Venturimeter is one of the most accurate devices for measuring the fluid flow rate
Venturi Meter is a device in which pressure energy is converted into kinetic energy and It used for measuring the flow rate (Discharge) of the system which is based on the Bernoulli's principle.
Parts of Venturi Meter:
A Venturi Meter is consisted Of:
Converging cone or Diameter (the area is decreasing)
Throat Diameter (the area is constant)
Diverging cone (the area is increasing)
Converging cone:
When water flowing through this cone the area is decreasing, therefore, the speed of flowing water increases and pressure decreases.
Throat Diameter:
When water flowing through this cone the area remains constant therefore the speed of flowing water and pressure remains constant.
Diverging cone:
When water flowing through this cone the area is increasing, therefore, the speed of flowing water decreases and pressure decreases.
Working Principle of Venturi Meter:
As I already told that Venturi Meter works on Bernoulli’s Principle, so let’s find out how it works?
Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy.
Suppose quantity of liquid v1 enter to the pipe, as per continuity equation volume flow rate at inlet (Q1), is equal to discharge at outlet (Q2), so if v1 amount of water enters to the inlet of the venturi meter the same amount of water should be discharged at outlet, that means at unit second v1/t1=v2/t2
As the area of section 1 (according to the above diagram) is more than area of the section , that means due to the decrease area the pressure at throttling section is decreased and velocity will be increased to maintain the flow (Q1=Q2)
In the throat position, the velocity of flow is maximum and pressure is minimum.
After throttling there again a diverging section (diffuser) in section 4 which restores the pressure as nearly possible to the actual value.
By this, we can easily determine the volume flow rate with the help of the U-Tube Manometer, by finding the pressure difference between section 1 (converging section) and section 2 which is throat.
Dimensions and Boundary conditions:
The Boundary conditions are specified as :
At inlet : Constant Velocity of 2.2m/s
At Outlet : Pressure of 1 bar
Wall Condition: Real wall
Fluid : Water with density of 1000 kg/m^3
Temperature is maintained at room temperature
Mesh Level: Level: 7 with Advanced Channel Refinement
Computational Domain:
Meshing:
Geometric Parameters Varied for Calculation:
Link to the model:
https://drive.google.com/drive/folders/1Pta2CkWY9Usv6ehMYbsW_R9z-UmxN5l9?usp=sharing
Pressure Cut plot obtained:
Flow Trajectory:
Results and Discussion:
By varying one parameter and keeping three parameters constant at a time, different geometries were analyzed by CFD analysis to investigate their effects on pressure drop.
Resultant plots:
The length of the divergent cone is made about three to four times long than that of the divergent cone in order to avoid tendency of breaking away the stream of liquid and to minimize friction losses. The velocity of liquid at the throat is higher than that of inlet.
diverging section of the venturi is kept so small compared to Convergent angle in order to to reduce the probability of flow separation and hence keeping the pressure recovering efficiency as high as possible.
Effect of different geometrical parameters of venturimeter like convergent cone angle, divergent cone angle, diameter ratio and throat length on pressure drop have been analyzed using SOLIDWORKS 2020 .Different geometries of venturimeter were made by varying one parameter and keeping three parameters constant at a time. From simulation results, following conclusions can be drawn:
Pressure drop decreases with increase in Diameter ratio (β)
By the Plots obtained it can be seen that Diameter ratio is a significant parameter in calculating pressure drop.
Maximum pressure drop occurs at Beta ratio of 0.3
With a Convergent Angle of 21 deg , throat length of 280 cm and Divergent Angle of 11 deg.
Minimum pressure drop occurs at Beta ratio of 0.7
with a Convergent Angle of 21 deg , throat length of 280 cm and Divergent Angle of 11 deg.
These results can be used in designing of venturi meter for particular application.
Applications of Venturi Meter:
Venturi Meter is used in various field like:
Calculating the flow rate of fluid that is Discharge in the pipe.
Plumbing.
Carburetor.
The flow of chemicals in pipelines.
This is widely used in large-diameter pipes such as found in the waste treatment process.
Also used in the medicine department for the measure, the flow rate of blood in arteries.
This also used where high-pressure recovery is required.
The advantages of Venturi Meter are:
Power loss is very less.
This can be used where a small head is available.
High reproducibility (the extent to which consistent results are obtained when an experiment is repeated).
Accuracy is high over wide flow ranges.
This can also be used for a compressible and incompressible fluid.
This device is easy to operate.
The coefficient of discharge (Cd ) for the venturi meter is high.
This is widely used for a high flow rate (Discharge)
Although there are few disadvantages of Venturi Meter, and those are:
The installation cost of a venturi meter is high.
There are little difficulties while maintenance.
This device can not be used where the pipe has a small diameter of 76.2 mm.
Non-linear.
This system occupies more space as compared to the orifice meter.
It has a limitation of the lower Reynolds number of 150,000.
It is expensive and a little bulky.