Week 9 - Parametric study on Gate valve.

Aim:-Parametric study on Gate valve.

Theory:-

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.

 

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 C_v (or flow-capacity rating of valve) can be expressed as :

`C_v=Qsqrt((SG)/(DeltaP)).`

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).

 

where

K_v is the flow factor (expressed in [`m^3.h^-1.Bar^(-0.5)`).

Q is the flowrate (expressed in cubic metres per hour [`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]).

K_v can be calculated from C_v using the equation :

Modelling approach :-

For valve uplifft 25 mm

 

For valve uplifft 40 mm

 

For valve uplifft 60 mm

 

For valve uplifft 75 mm

 

Mesh setting :-

Mesh overview

 

Mesh in detail

 

Cell information :-

 

Solving and Modelling approach:-

Boundary conditions :-

Inlet

Outlet

Turbulence model :-

Simulation parameter:-

 

Simulation method:

 

Run Parameter :-

 

Results :-

Convergence plot for different valve uplift :-

For 25 mm

For 40mm

For 60mm

For 75mm

 

Animation for different valve uplift:-

For 25mm

 

For 40mm

For 60mm

For 75mm

 

 

Velocity magnitude for different valve uplift :-                     

For 25mm                                                                                                                                                                                                                                                                        

 

For 40mm 

         

 

For 60mm 

 

For 75mm 

 

Pressure value for different valve uplift :-         

For 25mm

For 40mm

For 60mm

 

For 75mm 

Mass flow rate for different valve uplift :-

For 25mm

For 40mm

 

For 60mm

\

For 75mm

 

Here, Mass flow rate for different cases of valve uplift was as follow :-

S.No	Valve uplift	Mass flow rate
1.	25 mm	-0.28476
2.	40 mm	-0.45584
3.	60 mm	-0.63002
4.	75 mm	-0.73479

 

Here, Flow factor and flow coefficient for different cases of valve uplift was as follow :- 

S.No	Valve uplift	Flow coefficient(`C_V`)	Flow Factor (`K_V`)
1.	25 mm	121.20	105.00
2.	40 mm	210.00	181.20
3.	60 mm	316.20	273.00
4.	75 mm	412.80	357.00

 

 

 

 

 

Here, I can see clearly that Mass flow rate is increasing at outlet with respect to increase in uplift value of valve. This informs us that mass flow rate increases linearly with repect to uplift value of valve.

On the other hand, We also see that the flow factor and flow coefficient is also increasing with respect to uplift value of valve.

Mass flow rate and pressure drop is having  parabolic increase and linear decrease respectively with respect to increase in uplift value of valve. Whereas, Velocity magnitude is having steep increase with respect to uplift value of valve.
 

Conclusion:-

Increase in Valve uplift increases the mass flow rate. Similarly , it also leads to an increase in Flow factor and Flow coefficient. Hence, We concluded that Valve uplift have direct linear impact on Flow factor and mass flow rate.

On increase in Valve uplift, mass flow rate increases parabolic whereas pressure drop decrease linearly while velocity magnitude profile can't be determined.