Week 9 - Parametric study on Gate valve.

AIM: -

A. To Perform Simulation on the Gate Valve by Setting the Opening from 10% to 80%

B. To Calculate the Mass Flow rate and the Flow Factor for each Case

Given: -

A. The Given CAD Models of Gate Valves: -

The Gate Valve

Theories: -

A. Pressure Head Loss due to obstruction and Wall friction: -

For a Flow through a pipe, the pressure head of the fluid is lost due to Friction through the Walls, Bends in the Pipes, due to obstruction in the Flow, and many more. These losses either cause a major or a minor head loss, the following are the conditions for Major or Minor loss:-

i. Major Loss `->` Major loss is due to the friction experienced by the fluid from the walls of the pipe. These pressure energy losses are converted into thermal energy which increases the internal energy of the fluid and is conducted out of the pipe. These frictional losses can be calculated using Darcy-Weisbach Equation

Darcy-Weisbach Equation

Pressure Head Loss due to friction`(H_f) = fL/D(v^2)/(2g)`

ii. Minor Losses `->` Minor losses are due to bends in the pipe, sudden Contraction in the pipes, Sudden Expansion in the pipes, or obstruction in the flow. These losses don't cause any significant loss in energy and generally cause flow separation and vortex formation.

B. Flow Factor: -

The flow factor of a device is the relative measure of its efficiency in allowing fluid flow, it helps to relatively compare two conditions for the efficiency of flow. The Flow Factor can be Calculated by the Following Formula

FLow Factor`(K_V or C_V) = dot(m)sqrt((SG)/(triangleP))`

where, `dot(m) ->` The mass flow rate of the Fluid

`SG ->` Specific gravity of the Fluid

`triangleP ->` Pressure drop across the Obstruction

Steps to Setup The Gate Valve: -

A. Setting up the Ansys Workbench: -

Ansys Workbench `->` ToolBox `->` Analysis System `->` `ubrace("Fluid Flow(Fluent)")_("Selecting" -> "Holding" -> "Dragging and Drooping to Project Schematic")`

B. Opening SpaceClaim Geometry and Extracting Volume: -

i. Steps to Open SpaceClaim: -

Ansys Workbench `->` Project Schematic `->` Project `->` Geometry `->` Right-Click `->` Select SpaceClaim Geometry

ii. Steps to Load the Gate Valve Geometry: -

SpaceClaim `->` File `->` Open

iii. Steps to Pull the Inlet and Outlet of the Gate Valve: -

SpaceClaim `->` Sketch `->` Pull `->` `ubrace("Selected the desired Geometry and pulled")_("In this case Pulled Inlet for 200mm and Outlet for 400mm")`

iv. Steps to set the Movement of the Gate Valve in the Z direction: -

SpaceClaim `->` Sketch `->` Move `->` `ubrace("Selected the desired Components and pulled")_("In this case Selected the gate Valve and Spindle and Pulled in Z direction")` `->` In the Right Window Selected Group `->` Set Parameters `->` `ubrace("Set the Rule Dimensions")_("In our Cases set the rules to 10mm to 80mm at a step size of 10mm")`

Measuring the Cylinder	Sectional View of Solid and Fluid Volume

v. Steps to Extract Volume: -

SpaceClaim `->` Prepare `->` Volume Extract `->` Select Edges `->` Enter

Extracted Fluid Volume	Solid Casing and Fluid Volumes

C. Opening Mechanical(Meshing) and Meshing the Geometry: -

i. Steps to Open Meshing: -

Ansys Workbench `->` Project Schematic `->` Project `->` Mesh `->` Right-Click `->` Edit

ii. Steps to Name the Boundary: -

Mechanical(Meshing) `->` Model Working Window `->` Select the Boundary `->` Click N `->` Give the desired Name `->` Enter

iii. Steps to Create the Mesh: -

a. Setting Base Mesh Size: Outline Window `->` Select Mesh `->` Details of Mesh Window `->` Defaults `->` Element Size is set to "5mm"

Meshed Fluid Volume	Sectional View Meshed Fluid Volume
Spindle Threads Meshing	Casing and Gate Valve Meshing

D. Setuping the Physics and Boundary Conditions: -

i. Steps to Open Ansys Fluent: -

Ansys Workbench `->` Project Schematic `->` Project `->` Setup `->` Right-Click `->` Edit

ii. Steps to Check Mesh: -

Fluent `->` Outline View Window `->` Setup `->` General `->` Mesh `->` Check

iii. Steps to Set up the Physics: -

a. Setting Gravity: Fluent `->` Outline View `->` General `->` Select Gravity `->` `ubrace("Select Desired Magnitude")_("In our case Set Y direction to -9.81")`

b. Setting Viscous Model: Fluent `->` Physics `->` Models `->` Viscous `->` `ubrace("Select Desired Viscous Model")_("In our case Select K-Epsilon RNG Swirl Dominated Flow")`

c. Creating desired Materials: Fluent `->` Physics `->` Materials `->` Create/Edit... `->` `ubrace("Select/Create the desired Fluid")_("In our case, Select Water Liquid")` `->` Enter

d. Setting Cell Zones: Fluent `->` Physics `->` Zones `->` Cell Zone `->` `ubrace("Select the desired Zone")_("In our case, Selected Fluid_Volume")` `->` `ubrace("Set the Desired Type")_("Set the Type to Fluid")` `->` Edit `->` Set Desired Material to Water `->` Apply

iv. Steps to Set Boundary Conditions: -

Fluent `->` Physics `->` Zone `->` Boundaries `->` Select the desired Component `->` Select the Desired Type for that Component `->` Edit `->` Add the Values for the Component `->` Apply & Close

v. Steps to Initialize and Set Desired Graphical Views: -

a. Initializing: Fluent `->` Solution `->` Initialization `->` Initialize

b. Setting the desired Contour: Fluent `->` Results `->` Graphics `->` Contours `->` New `->` Rename `->` Select Variable for Contour of `->` Select Surface `->` Save/Display

Initialised Pressure Contour	Initialised Velocity Contour

Steps to Analyse the Gate Valve: -

A. Performing Calculations and Developing Results: -

i. Steps to Open Fluent: -

Ansys Workbench `->` Project Schematic `->` Project `->` Setup `->` Right-Click `->` Edit

ii. Steps to Run Calculations: -

a. Setting No. of Iterations: Fluent `->` Solution `->` Run Calculations `->` `ubrace("Setting Desired Iterations in No. of Iterations")_("In Our Case, No. of Iterations is set to 200")`

b. Running Calculations: Fluent `->` Solution `->` Run Calculations `->` Calculate

iii. Steps to Generate Desired Contours in CFD-Post(Results): -

a. Opening CFD-Post: Ansys Workbench `->` Project Schematic `->` Project `->` Results `->` Right-Click `->` Edit

b. Setting Desired Results on Fluid Boundaries: CFD-Post `->` Outline `->` FFF `->` Select Desired Boundary `->` Colour `->` Mode `->` Constants/Variables `->` Apply

c. Setting Desired Results on Volume: CFD-Post `->` Outline `->` User Loactions and Plot `->` Right-Click `->` Insert `->` Select Desired Method

iv. Steps to Perform Calculations from Parameters: -

Ansys Workbench `->` Project Schematic `->` Parameter Set `->` Set the desired Conditions `->` Right-Click on any new Set Condition `->` Update Selected Design Points

Generated Results/Plots: -

A. Mass Flow rate at different Gatve Valve Positions: -

Gate Valve Opening Along Z (mm)	Mass Flow Rate `((kg)/sec)`	Pressure Drop `(Pa)`	Flow Coefficient `(m^3/sec)`
10	0.20834	20	0.04654
20	0.33853	20	0.07563
30	0.51584	20	0.11524
40	0.6681	20	0.14926
50	0.79259	20	0.17707
60	0.92269	20	0.20613
70	1.0546	20	0.23560
80	1.1856	20	0.26487

B. For 10mm Open Gate Valve along Z: -

Pressure Contour	Velocity Contour
Velocity Vectors	Streamlines

C. For 40mm Open Gate Valve along Z: -

Pressure Contour	Velocity Contour
Velocity Vectors	Streamlines

D. For 80mm Open Gate Valve along Z: -

Pressure Contour	Velocity Contour
Velocity Vectors	Streamlines

Observations and Reasons: -

A. The Velocity and Pressure Relation: -

It can be observed that the Higher the Velocity the Lower the Velocity in that region. This is because the Total flow energy of the system is constant for the entire flow, as there is no energy added to the system in this scenario the pressure energy is converted into kinetic energy. From the results developed above, it can be observed that when the flow is more restricted, only a small fraction of the pressure ecanget is converted into kinetic energy because of flow obstruction. Due to this, the mass flow rate for those conditions is low.