OBJECTIVE
To perform a parametric study on valve simulation by lifting the disc from 10% to 80%.
To obtain the mass flow rate at the outlet for each design points.
To calculate flow coefficient and flow factor for each opening.
To describe the results of mass flow rate and flow coefficient.
THEORY
GATE VALVE
A gate valve is a valve with a wheel or circular handle on top that requires multiple rotations to open and close. Inside the valve is a circular disk (gate) that rides on a threaded rod that is attached to the handle. by turning the handle the gate goes down closing off the valve, by turning the other way the gate is raised opening the valve.
GEOMETRY
1.Hand Wheel
2.Spindle
3.Bottom
4.Bonnet
First, the disc is lifted by 10mm using the move tool and then click "P" which appear beside the lift specifying box, this enables the parametric
Then the inlet and outlet are extruded using the pull tool to about 800mm
Since we are dealing with determining the effects of mass flow rate we there extract the fluid volume out of the solid volume
Sectional view
Mesh
Element size:10mm
No of nodes:40190
No od elements:192573
Setup Details
Solver- Type: Pressure based.
Velocity formulation: Absolute.
Time: Steady-state approach.
Gravity--9.81m / s2 along z-direction
Viscous Model: k Espsilon Reliable, Scalable Wall Function
Material-fluid: water
Cell Zone condition-
Volume: Fluid water
Boundary Condition
Inlet
Type-Pressure inlet
Gauge Pressure-10Pa
Outlet
Type: Pressure-outlet
Guage Pressure-0Pa
Definition-
Flux Report: Mass flow rate at the outlet
No of Iteration:500
Results
Case I:10% Opening(ie 10mm)
Residual
Mass Flow Rate
Velocity Contour
Case II:20% Opening(ie 20mm)
Residual
Mass Flow Rate
Velocity Contour
Case III:30% Opening(ie 30mm)
Residual
Mass Flow Rate
Velocity Contour
Case IV:40% Opening(ie 40mm)
Residual
Mass Flow Rate
Velocity Contour
Case V:50% Opening(ie 50mm lift)
Residual
Mass Flow Rate
Velocity Contour
Case VI:60% Opening(ie 60mm lift)
Residual
Mass Flow Rate
Velocity Contour
Case VII:70% Opening(ie 70mm lift)
Case VIII:70% Opening(ie 80mm lift)
The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow. It describes the relationship between the pressure drop across an orifice valve or other assembly and the corresponding flow rate
Mathematically the flow coefficient Cv (or flow-capacity rating of the valve) can be expressed as :
- C v = Q SG Δ P {\displaystyle C_{v}=Q{\sqrt {\dfrac {\text{SG}}{\Delta P}}}}
where:
- Q is the rate of flow (expressed in US gallons per minute),
- SG is the specific gravity of the fluid (for water = 1),
- ΔP is the pressure drop across the valve (expressed in psi).
n more practical terms, the flow coefficient Cv is the volume (in US gallons) of water at 60 °F that will flow per minute through a valve with a pressure drop of 1 psi across the valve.
The metric equivalent flow factor (Kv; commonly used in Europe and Asia) is calculated using metric units :
- K v = Q SG Δ P {\displaystyle K_{v}=Q{\sqrt {\dfrac {\text{SG}}{\Delta P}}}}
where
- Kv is the flow factor (expressed in [ m 3 . h − 1 . b a r − 0.5 ] {\displaystyle [m^{3}.h^{-1}.bar^{-0.5}]}
). - Q is the flowrate (expressed in cubic metres per hour [ m 3 / h {\displaystyle m^{3}/h}
]), - SG is the specific gravity of the fluid (for water = 1),
- ∆P is the differential pressure across the device (expressed in [bar]).
Kv can be calculated from Cv using the equation
The density of water is =998.2kg/m^2
Pressure drop=10pa =0.0001bars=00.00145038psi
Flow Rate: Q=m/p
The mass flow which we get simulation has unit of m^3/s
Disc lift vs Flow Coefficient and Flow Factor
Conclusion
1. With an increase in a lift, it can be noted from the above plots and table that the mass flow rate increases which in turn conclude that higher the mass flow rate means lower is the pressure drop.
2. The trends for flow coefficient is as other parameters.
3. The flow coefficient helps us determining the sizing and selection for manufacturing.
- K v = 0.865 ⋅ C v {\displaystyle K_{v}=0.865\cdot C_{v}}