Parametric Study on a Gate Valve using ANSYS
Objective:
To conduct a parametric study on a gate valve and study the variation of flow coefficient for different amount of gate opening.
Introduction:
Gate valve is a type of valve that uses a gate or a wedge type disk and disk moves perpendicular to flow to start or stop the fluid flow in piping.
It is mainly used in process plants. It is a linear motion valve that can be used to start and stop fluid flow. They are mostly in fully open or fully closed condition
Types of gate Valves:
- Types of Disk:
- Solid Taper Wedge
- Flexible Wedge
- Split Wedge/Parallel Disk
- Types of Body Bonnet Joint
- Screwed Bonnet
- Bolted Bonnet
- Welded Bonnet
- Pressure Seal Bonnet
- Types of Stem Movement
- Rising Stem
- Non-Rising Stem type
Flow Coefficient:
The flow coefficient of a device is relative measure of its efficiency at allowing fluid flow. It describes the relationship between pressure drop across a valve and the corresponding flow rate.
Flow Coefficient is the volume of water at 60-degree Fahrenheit that will flow per minute through a valve with a pressure drop of 1 psi across the valve.
Flow coefficient is a standard method of comparing valve capacities and sizing valves for specific applications.
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Q is rate of flow (gallons per minute)
SG is specific gravity
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Flow Factor is calculated using metric units.
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Q is rate of flow (m3/hr)
SG is specific gravity
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Geometry:
The given gate valve can be seen in the figure below:
In order to conduct the parametric study, the ends of the valve are extruded out in order to create an inlet and outlet.
The gate valve is lifted by 10 mm using the move option and a parameter is created for the lift value.
The bonnet is hidden and the fluid volume to be analyzed in created and the update geometry from current option is selected.
Meshing:
A mesh is created .
The Inlet and Outlet are the named selections. The following figure shows the named selections.
Case Setup:
A steady state simulation is conducted with gravity enabled.
Working Fluids: Water
Turbulence Model: k-epsilon, realizable model with scalable wall function is used.
Boundary Conditions:
Inlet: Pressure Inlet with 10 Pa
Outlet: Pressure Outlet 0 Pa
Walls: Wall Boundary condition.
Report Definitions: An Output parameter is created for the mass flux through the Output.
Parametric Study:
The opening of the gate valve disk that is created as a parameter during the geometry setup can be changed in the Parameters Tab in Ansys Workbench.
Different valve lift values are entered in the Parameters Tab and the solution is updated for all design points.
Results:
The parameter tab gives the value of mass flow rate is the output parameter and is updated for each of the design points.
Similarly parameters are setup for more design points.
Each Design Point is set as current and the velocity flow contour for each case is taken.
The flow factor and coefficient is calculated in each case.
| Opening(mm) | Mass Flow(kg/s) | Flow Coefficient | Flow Factor |
| 10 | 0.14871 | 62.10 | 53.72 |
| 15 | 0.18798 | 78.50 | 67.90 |
| 20 | 0.23811 | 99.43 | 86.01 |
| 25 | 0.29543 | 123.37 | 106.72 |
| 30 | 0.35702 | 149.09 | 128.96 |
| 40 | 0.46612 | 194.65 | 168.37 |
| 50 | 0.55534 | 231.91 | 200.60 |
| 60 | 0.63946 | 267.04 | 230.99 |
| 70 | 0.67 | 279.79 | 242.02 |
| 80 | 0.7106 | 296.75 | 256.69 |
| 90 | 0.824 | 344.10 | 294.90 |
The following plot shows the variation of flow coefficient with valve opening.
It can be seen that the flow coefficient increases with increase in the gate disc rise.
The velocity Contours for each case can be observed in the figures below:
Velocity for 10mm rise:
Velocity for 15mm rise:
Velocity for 20mm rise:
Velocity for 25mm rise:
Velocity for 30mm rise:
Velocity for 40mm rise:
Velocity for 50mm rise:
Velocity for 60mm rise:
Velocity for 70mm rise:
Velocity for 90mm rise:
It can be observed from the velocity contours that the overall flow velocity of the fluid increases with increasing of the opening of the gate valve. For small openings of the gate valve the velocity decreases at the obstruction created by the valve and as the valve opened the flow velocity increases.
Conclusion:
The variation of the flow coefficient and flow factor with the opening of the valve is studied by conducting a parametric study on the valve by using the gate valve movement as a parameter.
The velocity of the flow and the Flow coefficient id found to be increasing with increase in the valve opening.