Gate Valve Parametric Study

AIM :

To perform a parametric study on the gate valve simulation by setting the opening from 10 % to 80%.

To

• obtain the mass flow rates at the outlet for each design point.
• calculate the flow coefficient and flow factor for each opening and plot the graph.
• discuss the results of the mass flow rate and flow coefficient.

Introduction:

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 (in order 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.

CASE SETUP:

Geometry:

The following is the model of gate valve which we used for the simulation.

The fluid volume is extracted and made 800mm of fluid region

The following is the region where we concentrane on opening of certain percentage of raise of gate and how fluid varies.

Mesh:

The following is the Mesh and its details.

Setup:

Pressure based steady solver is used.

Model = K-Epsilon with RNG and scalable wall functions enabled.

Material used = water liquid

Boundary Conditions: Inlet = Pressure-inlet

outlet = pressure-outlet

Standard Initialization

Results and Discussions:

Case-1:

Position of gate valve at 10mm.

Residuals:

Mass Flow rate:

Velocity Contour:

https://drive.google.com/file/d/1TGopN2JE0m7sIbJ-MvrWTd9MftSPl6DU/view?usp=sharing

Case-2:

Position of gate valve at 50mm.

Residuals:

Mass flow rate:

Velocity Contour:

Case-3:

Position of gate valve at 80mm.

Residual Plot:

Mass flow rate:

Velocity Contour:

https://drive.google.com/file/d/1U-e11RoaNPhQvxIU4t6OCq6NB6zfGTuK/view?usp=sharing

Flow coefficient:

It describes the relation between pressure drop across the Orifice value and the flow rate.

Flow coefficient = Cv = Q*(SG/deltaP)^(1/2)

where Q = flow rate, SG = specific gravity, deltaP = pressure drop.

The metric equivalent flow factor is calculated by

Kv = Q*(SG/deltaP)^(1/2)

         where Kv in m^3*h^(-1)*bar^(-0.5)

                   Q = 1kg/s =3.6 in m^3/h

deltaP = 10-0 = 10pa = 10*10^-5bar = 10^-4



80% = Kv = 3.6*0.8468*1/((10^-4)^1/2) = 304.848 m^3*h^(-1)*bar^(-0.5)

50% = Kv = 252 m^3*h^(-1)*bar^(-0.5)

10% = Kv = 129 m^3*h^(-1)*bar^(-0.5) 

Conclusion:

Increase in the percentage of lift of gate increases Mass flow rate.

Parametric study helps to reduce time to study certain parameters depends on system.