Week 9 - Parametric study on Gate valve.

AIM :

To perform a parametric study of flow through the gate valve by setting the valve opening from 10% to 80%.

OBJECTIVES :

• To import the given gate valve model into spaceclaim and extrude the pipe side surfaces of the valve to 800mm.
• To set the lift of the gate valve disc as the input parameter for the simulation.
• To extract the fluid volume for the model.
• To generate mesh for the fluid volume.
• To setup the simulation by choosing the necessary solvers and, to create the mass flow rate as the ouput parameter.
• To post process the simulation results by creating the velocity contour and velocity vectors in YZ plane of the model.
• Similarly to increase the lift of the gate disc in the input parameter of the parameter set tab from workbench and update the respective design points to obtain the mass flow rate for each gate valve positions.

INTRODUCTION :

In this challenge, we are rying to study how the mass flow rate is going to change for different lifts of the gaye disc, so the only change in the case setup will be lift of the gate valve. By parameterizing the lift value, we are essentially automating the mesh, setup, solution and post processing stages which saves time and also more effective.

Gate valve :

• 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.
• They can be found in petrochemical industries, power plans and widely in the pipeline industries.

Flow factor :

The kV-factor for a given valve is a constant which in a simple way states the valve capacity. The kV-factor is determined by the valve manufacturer by experiments. The kV factor specifies the water flow in m3 through the valve in one hour at a pressure drop across the valve of 1Bar

The metric equivalent flow factor (K_v) is calculated using metric units.

where,

K_v is the flow factor (expressed in m³·h⁻¹).

Q is the flowrate (expressed in cubic metres per hour m³·h⁻¹),

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,

The k_v factor or value as it is also called is defined in VDI/VDE Richtlinien No. 2173. A simplified version of the definition is: The k_v factor of a valve indicates "The water flow in m³/h, at a pressure drop across the valve of 1 kgf/cm² when the valve is completely open.

Flow coefficient :

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 :

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).

CASE SETUP :

• The following case studies are set for this simulation.

	GATE VALVE POSITION (in 'mm')	GAUGE PRESSURE AT INLET (in 'Pa')	GAUGE PRESSURE AT OUTLET (in 'Pa')	PRESSURE DIFFERENCE `(DeltaP)`
				(in 'Pa')	(in 'bar')
CASE - 1	10	10	0	10	0.0001
CASE - 2	20	10	0	10	0.0001
CASE - 3	30	10	0	10	0.0001
CASE - 4	40	10	0	10	0.0001
CASE - 5	50	10	0	10	0.0001
CASE - 6	60	10	0	10	0.0001
CASE - 7	70	10	0	10	0.0001
CASE - 8	80	10	0	10	0.0001

PROCEDURE :

CASE 1 (Gate valve lift - 10mm) :

PRE-PROCESSING :

• Import the given gate valve model into spaceclaim and use the pull tool to extend either sides of the valve pipe to 800mm.

• To provide gate valve lift, isolate the gate disc and spindle, and move those components to 10mm in positive z-direction using move tool under design tab. Now, click the Create parameter option under Groups tab to create it as the input parameter for the simulation.

• Hide the bonnet and hand wheel, and use Volume Extract option under Prepare tab to extract the fluid volume by selecting the edges of the fluid domain in the gate valve model.

• Make sure that the fluid volume is extracted properly and also the lift of the gate valve is set to 10mm.

• The inner diameter of the valve pipe in which the fluid is flowing, is measured to be 100mm. So, for 10% to 80% of the gate valve opening, the lift of the gate valve which is given as the input parameter, is to be taken from 10mm to 80mm with 10mm increment. Now, close the spaceclaim.

• Open the mesh window and give the required named selections for model. Now, generate the mesh by choosing the mesh element size as 10mm and the maximum mesh size also to be 10mm which generates a uniform mesh.

• Since most number of the mesh elements have about 88% of element quality, the mesh quality is good for the simulation.

• Cross sectional view

Cells	Faces	Nodes
226230	468271	45834

SETUP AND SOLVING :

• Setup the simulation by providing the following input parameters in the setup window.

Model	Settings
Space	3D

Time	Steady
Viscous	RNG k-epsilon turbulence model
Wall Treatment	Standard Wall Functions
RNG Swirl Dominated Flow Option	Enabled

Material properties :

Fluid	water-liquid
Density	998.2 kg/m^3
Cp (Specific Heat)	4182 J/(kg K)
Thermal Conductivity	0.6 W/(m K)
Viscosity	0.001003 kg/(m s)
Molecular Weight	18.0152 kg/kmol

Boundary conditions :

inlet
Reference Frame	Absolute
Gauge Total Pressure [Pa]	10
Supersonic/Initial Gauge Pressure [Pa]	0
Direction Specification Method	Normal to Boundary
outlet

Backflow Reference Frame	Absolute
Gauge Pressure [Pa]	0
Backflow Direction Specification Method	Normal to Boundary
wall-volume_volume
Wall Motion	Stationary Wall
Shear Boundary Condition	No Slip

Solution method :

Pressure-Velocity Coupling

Coupled

• Here, we enable the gravity having value of 9.81 m/s^2 in negative z-direction since the gravity acts perpendicular to the direction of flow in this setup.

• For this setup, we choose k-epsilon RNG turbulence model with swirl dominated flow option enabled since this visous model will be the better option for incompressible flows having swirling effects.

• Select the fluid material as water from fluent database.

• Make sure the fluid material for the fluid domain cell zone is set to water.

• Set the boundary condition type for inlet as pressure inlet with total gauge pressure of 10 Pa.

• For outlet, select the type as pressure outlet with gauge pressure of 0 Pa (open to atmosphere).

• Create the report definition for mass flow rate at outlet and enable the create parameter option to set it as the output parameter for the simulation.

• Initialize the simulation using hybrid initialization.

• Run the simulation for 500 iterations.

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 87th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.0009723831	0.001	Converged
x-velocity	8.342491e-05	0.001	Converged
y-velocity	0.0001238028	0.001	Converged
z-velocity	9.265241e-05	0.001	Converged
k	0.000301145	0.001	Converged
epsilon	0.0005590986	0.001	Converged

Report definitions :

mass_flow_rate

-0.1426206

kg/s

Volumetric Flow Rate

-0.00014287778

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 2 (Gate valve lift - 20mm) :

• Create another design point in the Parameter set window from workbench by giving the valve lift value as 20mm under input parameter and update the design point. The fluent will automatically update the geometry, mesh , setup, solution and results for the specified lift value, and also will give the value of mass flow rate at outlet which was set as the output parameter.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
224561	464568	45389

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 100th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.0009978	0.001	Converged
x-velocity	4.090286e-06	0.001	Converged
y-velocity	6.937372e-06	0.001	Converged
z-velocity	4.282387e-06	0.001	Converged
k	3.531111e-05	0.001	Converged
epsilon	7.813134e-05	0.001	Converged

Report definitions :

mass_flow_rate

-0.2293705

kg/s

• The negative sign in the mass flow rate indicates that the fluid is leaving the system.

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.2293705/998.2

Volumetric Flow Rate

-0.000229784

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 3 (Gate valve lift - 30mm) :

• Create another design point in the Parameter set window for lift value of 30mm and update the design point.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
222083	459284	44824

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 200th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.0267538	0.001	Not Converged
x-velocity	8.868771e-05	0.001	Converged
y-velocity	0.0002176496	0.001	Converged
z-velocity	0.0001000305	0.001	Converged
k	0.009749514	0.001	Not Converged
epsilon	2.738883	0.001	Not Converged

Report definitions :

mass_flow_rate

-0.3468929

kg/s

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.3468929/998.2

Volumetric Flow Rate

-0.0003475184

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 4 (Gate valve lift - 40mm) :

• Create another design point in the Parameter set window for lift value of 40mm and update the design point.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
219283	453406	44232

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET - PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 200th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.02798982	0.001	Not Converged
x-velocity	7.86329e-05	0.001	Converged
y-velocity	0.0002134795	0.001	Converged
z-velocity	9.09735e-05	0.001	Converged
k	0.00964965	0.001	Not Converged
epsilon	0.3102351	0.001	Not Converged

Report definitions :

mass_flow_rate

-0.4503665

kg/s

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.4503665/998.2

Volumetric Flow Rate

-0.0004511786

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 5 (Gate valve lift - 50mm) :

• Create another design point in the Parameter set window for lift value of 50mm and update the design point.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
218410	451550	44040

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET - PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 450th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.3740099	0.001	Not Converged
x-velocity	0.00269189	0.001	Not Converged
y-velocity	0.003484739	0.001	Not Converged
z-velocity	0.002710014	0.001	Not Converged
k	0.09197593	0.001	Not Converged
epsilon	0.2623293	0.001	Not Converged

Report definitions :

mass_flow_rate

-0.5353329

kg/s

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.5353329/998.2

Volumetric Flow Rate

-0.000536298

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 6 (Gate valve lift - 60mm) :

• Create another design point in the Parameter set window for lift value of 60mm and update the design point.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
217210	449059	43784

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET - PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 250th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.03571703	0.001	Not Converged
x-velocity	0.0001077264	0.001	Converged
y-velocity	0.0004059597	0.001	Converged
z-velocity	0.0001022925	0.001	Converged
k	0.1995665	0.001	Not Converged
epsilon	0.8470737	0.001	Not Converged

Report definitions :

mass_flow_rate

-0.6296555

kg/s

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.6296555/998.2

Volumetric Flow Rate

-0.0006307909

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 7 (Gate valve lift - 70mm) :

• Create another design point in the Parameter set window for lift value of 70mm and update the design point.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
216311	447186	43598

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET - PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 450th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.03242812	0.001	Not Converged
x-velocity	6.798382e-05	0.001	Converged
y-velocity	0.000274682	0.001	Converged
z-velocity	7.156774e-05	0.001	Converged
k	0.03291835	0.001	Not Converged
epsilon	1.557364	0.001	Not Converged

Report definitions :

mass_flow_rate

-0.7082934

kg/s

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.7082934/998.2

Volumetric Flow Rate

-0.0007095706

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

CASE 8 (Gate valve lift - 80mm) :

• Create another design point in the Parameter set window for lift value of 80mm and update the design point.

PRE-PROCESSING :

• Cross sectional view of the gate valve with fluid volume.

• Cross sectional view of the mesh elements for the fluid volume.

Cells	Faces	Nodes
214982	444437	43339

RESIDUALS PLOT :

MASS FLOW RATE AT OUTLET - PLOT :

Solution status :

• From the above plots, we see that the solution got converged at 450th iteration since the rate at which residuals and mass flow rate at oulet value changes become constant over iteration.

	Value	Absolute Criteria	Convergence Status
continuity	0.03739197	0.001	Not Converged
x-velocity	8.598935e-05	0.001	Converged
y-velocity	0.0002903818	0.001	Converged
z-velocity	0.0001033664	0.001	Converged
k	0.06905487	0.001	Not Converged
epsilon	0.3593759	0.001	Not Converged

Report definitions :

mass_flow_rate

-0.7851822

kg/s

Calculation of Volumetric flow rate :

We know that,

Volume flow rate (Q) = Mass flow rate / Density of the fluid (water)

Q = 0.7851822/998.2

Volumetric Flow Rate

-0.00078659807

m^3/s

POST PROCESSING :

VELOCITY CONTOUR :

VELOCITY VECTORS :

RESULTS :

Google drive link of the file :

https://drive.google.com/file/d/1t4p81g6DbpaTI4GW87I4UhcRT0DPFNIy/view?usp=share_link

Streamlines :

For 10mm valve height,

For 20mm valve height,

For 30mm valve height,

For 40mm valve height,

For 50mm valve height,

For 60mm valve height,

For 70mm valve height,

For 80mm valve height,

Parameter set window :

	GATE VALVE POSITION (in 'mm')	NUMBER OF MESH ELEMENTS	MASS FLOW RATE AT OUTLET (in 'kg/s')	VOLUMETRIC FLOW RATE (Q)		GAUGE PRESSURE DIFFERENCE ACROSS THE VALVE (in 'bar')	FLOW FACTOR `(K_V)`	FLOW COEFFICIENT `(C_V)`
				(in 'm^3/s')	(in 'm^3/hr')
CASE - 1	10	226230	0.1426206	0.00014287778	0.51436	0.0001	51.436	59.4636
CASE - 2	20	224561	0.2293705	0.000229784	0.8272224	0.0001	82.722	95.6326
CASE - 3	30	222083	0.3468929	0.0003475184	1.251066	0.0001	125.1066	144.632
CASE - 4	40	219283	0.4503665	0.0004511786	1.624243	0.0001	162.4243	187.774
CASE - 5	50	218410	0.5353329	0.000536298	1.930673	0.0001	193.0673	223.199
CASE - 6	60	217210	0.6296555	0.0006307909	2.270847	0.0001	227.0847	262.5257
CASE - 7	70	216311	0.7082934	0.0007095706	2.55445	0.0001	255.445	295.312
CASE - 8	80	214982	0.7851822	0.00078659807	2.83175	0.0001	283.175	327.37

Mass flow rate for different valve position :