Week 9 - Parametric study on Gate valve.
Gate Valve:-
A gate valve, also known as a sluice valve, is a valve that opens by lifting a barrier (gate) out of the path of the fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened. The gate faces can be parallel but are most commonly wedge-shaped (to be able to apply pressure on the sealing surface). Gate valves are used to shut off the flow of liquids rather than for flow regulation. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low flow resistance. The size of the open flow path generally varies in a nonlinear manner as the gate is moved. This means that the flow rate does not change evenly with stem travel. Depending on the construction, a partially open gate can vibrate from the fluid flow. Gate valves are mostly used with larger pipe diameters (from 2" to the largest pipelines) since they are less complex to construct than other types of valves in large sizes. At high pressures, friction can become a problem. As the gate is pushed against its guiding rail by the pressure of the medium, it becomes harder to operate the valve. Large gate valves are sometimes fitted with a bypass controlled by a smaller valve to be able to reduce the pressure before operating the gate valve itself. Gate valves without an extra sealing ring on the gate or the seat are used in applications where minor leaking of the valve is not an issue, such as heating circuits or sewer pipes.
Parametric study and Analysis:-
A parametric study in the product design model helps to explore design alternatives that effectively support product concept designs. A parametric study is simple and easy to perform as long as the mapping between CAD and simulation models has been established. The mapping supports fast simulation model generation for performance analyses.
Parametric Analysis of Gate Valve:-
Objective:-
To perform gate valve simulation by setting the opening from 10 % to 80% and to obtain mass-flow rate in each case and calculate the flow coefficient and flow factor.
Geometry:-
Volume Extracted:-
Mesh Generated:-
Element size = 5mm
Case Setup:-
General setting: -
Analysis type:- Steady-state
Solver:- Pressure based solver
Fluid :- Water-liquid (h2o-l)
Viscous Model:-
Model :- k-Epsilon
k-Epsilon Model:- Realizable
Near Wall Tratment:- Scalable wall Functions
Boundary Conditions:-
Standard initialization is done and velocity is obtained.
Calculating Reynolds No.,
`Re = (rho* V*D)/ mu`
Re = ( 998.2*0.141588*0.1)/0.001003
Re = 14087.13
As, Reynolds No, is more than 2000, flow is turbulent.
Analysis Results:-
Case-1:- Gate disc lift = 10 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.14940121
velocity contour:-
velocity vector:-
Case-2:- Gate disc lift = 20 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.24054187
velocity contour:-
velocity vector:-
Case-3:- Gate disc lift = 30 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.36340763
velocity contour:-
velocity vector:-
Case-4:- Gate disc lift = 40 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.47310704
velocity contour:-
velocity vector:-
Case-5:- Gate disc lift = 50 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.56414922
velocity contour:-
velocity vector:-
Case-6:- Gate disc lift = 60 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.63703529
velocity contour:-
velocity vector:-
Case-7:- Gate disc lift = 70 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.71550861
velocity contour:-
velocity vector:-
Case-8:- Gate disc lift = 80 mm
Scaled residuals:-
mass-flow rate plot:-
Mass-Flow Rate = -0.78097883
velocity contour:-
velocity vector:-
Flow Coefficient (Cv):-
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).
Flow Factor(Kv):-
Where,
Kv is the flow factor (expressed in {\displaystyle [m^{3}.h^{-1}]}
).
Q is the flowrate (expressed in cubic metres per hour [{\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,
| Sr.No. | Gate Disc Lift (mm) | Mass Flow rate (Kg/s) | Flow Coefficient (Cv) | Flow Factor (kv) |
| 1 | 10 | 0.14940121 | 62.218 | 53.818 |
| 2 | 20 | 0.24054187 | 100.022 | 86.519 |
| 3 | 30 | 0.36340763 | 151.214 | 130.800 |
| 4 | 40 | 0.47310704 | 196.893 | 170.312 |
| 5 | 50 | 0.56414922 | 234.696 | 203.012 |
| 6 | 60 | 0.63703529 | 265.149 | 229.353 |
| 7 | 70 | 0.71550861 | 297.702 | 257.512 |
| 8 | 80 | 0.78097883 | 325.004 | 281.128 |
Conclusion:-
1. As gate disc lift increases mass flow rate also increases and therefore, flow coefficient and flow factor also increases.
2. Parametric study is helpful to analyze the different positions of valve opening and gives the benefit to get result quickly and easily.