Week 9 - Parametric study on Gate valve.

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

OBJECTIVE:-

1.To simulate the flow of fluid through a gate valve.

2.To obtain the mass flow rates at the outlet for each design point.

3.To calculate the flow coefficient and flow factor for each opening and plot the graph.

4.Discuss the results of the mass flow rate and flow coefficient.

DESCRIPTION:-

A Gate valve also known as 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 restict 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 the pressure on the sealing surface.

Main components of the gate valve are body, seat, stem, bonnet and actuator.The main operation mechanism is very simple.When the hand wheel is turned it rotates the fluid which is translated into the vertical movement of the gate disc via threads.They are considered multi-turn valves as it makes more than one 360 degree turn to fully open/close the valve. When the gate is lifted from the path of the flow,the valve opens and when it returns to its closed position, it seals the bore resulting in a full closure of the valve.

PARAMETRIC STUDY:-

One of the best ways to get value out of yoour simulation is to do parametric analysis with very little marginal work with a model which can be parameterized to simulate scenarios limited only by computational time and resources. As you move forward in your design you can access the impact that is changing the certain parameters accordingly to the design criteria.The parameters can include dimensional parameters. Parametricc studies sllow you to nominate parameters for evaluation, define the parameter range, specify the design constraints and analyse the results of each parameter variation.

A parametric study requires the following

1.Design objective is set to parametric dimensions.

2.Parameters nominated for use in the simulation

3.Design criteria specified

4.Various configurations generated.

FLOW COEFFICIENT:-

The flow coefficient of a device is 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 or flow capacity rating Cv can be expressed as

Cv=Q√SGΔPCv=QSGΔP

Where Q is the rate of flow (gallons per minute)

SG is the specific gravity of fluid (for water =1)

ΔPΔP is the pressure drop across the valve expressed in psi.

10 Pa = 0.00145038 psi

The use of flow coefficient offers a standard method of comparing valve capacities and sizing valves for specific applications that are widely accepted by the industry.The general definition of the flow coefficient can be expanded into equations modelling the flow of liquids, gases and steam using the discharge coefficient.

FLOW FACTOR:-

The metric equivalent factor Kv commonly used in europe and Aisa is calculated using metric units

Kv=Q√SGΔPKv=QSGΔP

Kv can be calculated from Cv using the equation as given below

Kv = 0.865Cv

The Kv factor of the valve indicates, The water flow m3/h at a pressure drop across the valve of 1kgf/cm2 when the valve is completely open.

Opening the space claim and opening the Gate valve model

The model looks as follows

First we will do for the case without parametric study

Now hiding the bottom surface and then gate disc is visible and using move tool with component selection and move the gate disc in upward z direction for 10mm.

Now extracting the fluid volume from prepare>volume extract>edges select inlet and outlet and part under bonet.

Next using the pull tool pulling the inlet by 800mm and for output also 800mm.

Now going for meshing

Generating a generaal mesh

Next is naming the parts.

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 (ΔP)(ΔP)
				(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.

• 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

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

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

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

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

VELOCITY CONTOUR :-

VELOCITY VECTORS :-

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 (KV)(KV)	FLOW COEFFICIENT (CV)(CV)
				(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 :