Week 9 - Parametric study on Gate valve.
AIM AND OBJECTIVE
1. OBTAIN THE MASS FLOW RATES AT THE OUTLET FOR EACH DESIGN POINT
2. CALCULATE THE FLOW COEFFICIENT AND FLOW FACTOR FOR EACH OPENING AND PLT HTE GRAPH
3. DISCUSS THE RESULTS OF THE MASS FLOW RATE AND FLOW COEFFIECIENT
INTRODUCTION:
A GATE VALVE IS A TYPE OF LINEAR MOTION VALVE THAT IS USED TO CONTROL THE FLOW OF FLUIDS, TYPICALLY IN A PIPELINE. IT IS NAMED AFTER ITS GATE-SHAPED DISK THAT SLIDES PERPENDICULAR TO THE FLOW OF THE FLUID TO OPEN OR CLOSE THE VALVE. WHEN THE GATE IS FULLY RAISED, THE VALVE IS IN THE FULLY OPEN POSITION, ALLOWING UNRESTRICTED FLOW OF THE FLUID. WHEN THE GATE IS FULLY LOWERED, THE VALVE IS IN THE FULLY CLOSED POSITION, STOPPING THE FLOW OF THE FLUID.
GATE VALVES ARE COMMONLY USED IN A WIDE RANGE OF APPLICATIONS, INCLUDING WATER AND WASTEWATER SYSTEMS, OIL AND GAS PIPELINES, POWER PLANTS, AND INDUSTRIAL PROCESSES. THEY ARE KNOWN FOR THEIR ABILITY TO PROVIDE TIGHT SHUTOFF, LOW PRESSURE DROP, AND HIGH FLOW CAPACITY, MAKING THEM SUITABLE FOR BOTH ON/OFF AND THROTTLING APPLICATIONS. GATE VALVES ARE AVAILABLE IN DIFFERENT SIZES, MATERIALS, AND CONFIGURATIONS, SUCH AS RISING STEM OR NON-RISING STEM, WEDGE OR PARALLEL DISK, AND VARIOUS END CONNECTIONS, TO MEET DIFFERENT REQUIREMENTS AND OPERATING CONDITIONS.
A GATE VALVE TYPICALLY CONSISTS OF SEVERAL KEY PARTS, INCLUDING:
BODY: THE BODY OF THE GATE VALVE IS THE MAIN HOUSING THAT CONTAINS THE GATE AND OTHER INTERNAL COMPONENTS. IT IS TYPICALLY MADE OF METAL, SUCH AS CAST IRON, CAST STEEL, OR STAINLESS STEEL, AND IS DESIGNED TO WITHSTAND THE PRESSURE AND TEMPERATURE OF THE FLUID BEING HANDLED.
GATE: THE GATE IS THE MAIN COMPONENT OF THE GATE VALVE THAT CONTROLS THE FLOW OF THE FLUID. IT IS A FLAT OR WEDGE-SHAPED DISK THAT MOVES PERPENDICULAR TO THE DIRECTION OF THE FLUID FLOW TO OPEN OR CLOSE THE VALVE. THE GATE IS TYPICALLY MADE OF METAL, SUCH AS BRASS, BRONZE, OR STAINLESS STEEL, AND MAY HAVE A COATING OR LINING FOR IMPROVED WEAR RESISTANCE.
STEM: THE STEM IS THE PART OF THE GATE VALVE THAT CONNECTS THE GATE TO THE ACTUATOR OR HANDLE. IT ALLOWS THE OPERATOR TO MOVE THE GATE UP OR DOWN TO OPEN OR CLOSE THE VALVE. THE STEM MAY BE THREADED OR NON-THREADED, DEPENDING ON THE DESIGN OF THE GATE VALVE.
BONNET: THE BONNET IS THE COVER OR CAP THAT IS ATTACHED TO THE BODY OF THE GATE VALVE AND PROVIDES A SEAL TO PREVENT LEAKAGE. IT MAY ALSO HOUSE THE PACKING GLAND OR PACKING BOX, WHICH HELPS TO SEAL THE STEM AND PREVENT LEAKAGE ALONG THE STEM.
PACKING GLAND OR PACKING BOX: THE PACKING GLAND OR PACKING BOX IS A PART OF THE GATE VALVE THAT SURROUNDS THE STEM AND PROVIDES A SEAL TO PREVENT LEAKAGE ALONG THE STEM. IT TYPICALLY CONTAINS PACKING MATERIAL, SUCH AS PTFE (POLYTETRAFLUOROETHYLENE) OR GRAPHITE, WHICH CAN BE TIGHTENED OR LOOSENED TO ADJUST THE TIGHTNESS OF THE SEAL.
HANDWHEEL OR ACTUATOR: THE HANDWHEEL OR ACTUATOR IS THE PART OF THE GATE VALVE THAT IS USED TO OPERATE THE VALVE AND MOVE THE GATE UP OR DOWN. IT MAY BE A HAND-OPERATED WHEEL, LEVER, OR GEAR, OR IT MAY BE POWERED BY AN ELECTRIC MOTOR, PNEUMATIC ACTUATOR, OR HYDRAULIC ACTUATOR, DEPENDING ON THE SIZE AND TYPE OF THE GATE VALVE.
SEATS: THE SEATS ARE THE SEALING SURFACES ON WHICH THE GATE RESTS WHEN THE VALVE IS IN THE FULLY CLOSED POSITION. THEY ARE TYPICALLY MADE OF METAL OR OTHER MATERIALS WITH GOOD SEALING PROPERTIES, AND THEY ENSURE A TIGHT SHUTOFF OF THE FLUID FLOW WHEN THE GATE IS FULLY CLOSED.
FLANGES OR CONNECTIONS: THE FLANGES OR CONNECTIONS ARE THE PARTS OF THE GATE VALVE THAT ALLOW IT TO BE CONNECTED TO THE PIPELINE OR OTHER SYSTEM COMPONENTS. THEY MAY BE THREADED, BOLTED, OR WELDED, AND THEY PROVIDE A SECURE AND LEAK-TIGHT CONNECTION BETWEEN THE GATE VALVE AND THE ADJOINING PIPING OR EQUIPMENT.
SCHEMATIC FLOW OF WATER THROUGH THE GATE VALVE.
FLOW COEFFICIENT FORMULA:
THE FLOW COEFFICIENT, ALSO KNOWN AS CV, IS A DIMENSIONLESS PARAMETER USED TO CHARACTERIZE THE FLOW CAPACITY OF A VALVE OR OTHER FLUID CONTROL DEVICE. IT IS TYPICALLY USED IN THE FIELD OF FLUID DYNAMICS AND IS DEFINED AS THE FLOW RATE OF WATER (IN GALLONS PER MINUTE, GPM) THAT PASSES THROUGH A VALVE WITH A PRESSURE DROP OF 1 PSI (POUND PER SQUARE INCH) ACROSS THE VALVE.
THE FORMULA FOR CALCULATING THE FLOW COEFFICIENT (CV) IS:
CV = Q / (ΔP √SG)
WHERE:
CV = FLOW COEFFICIENT
Q = FLOW RATE OF WATER (IN GPM)
ΔP = PRESSURE DROP ACROSS THE VALVE (IN PSI)
SG = SPECIFIC GRAVITY OF THE FLUID
THE SPECIFIC GRAVITY (SG) IS THE RATIO OF THE DENSITY OF THE FLUID TO THE DENSITY OF WATER AT A SPECIFIED TEMPERATURE AND PRESSURE. FOR WATER AT ROOM TEMPERATURE (20°C) AND ATMOSPHERIC PRESSURE, THE SPECIFIC GRAVITY IS APPROXIMATELY 1.
IT'S IMPORTANT TO NOTE THAT THE FLOW COEFFICIENT (CV) IS A STANDARDIZED PARAMETER THAT IS TYPICALLY PROVIDED BY VALVE MANUFACTURERS FOR THEIR SPECIFIC PRODUCTS, AND IT MAY VARY DEPENDING ON THE DESIGN, SIZE, AND TYPE OF THE VALVE. THE CV VALUE IS USED TO COMPARE THE FLOW CAPACITIES OF DIFFERENT VALVES AND SELECT THE APPROPRIATE VALVE FOR A GIVEN APPLICATION TO ENSURE PROPER FLOW CONTROL.
FLOW FACTOR FORMULA:
THE METRIC EQUIVALENT OF THE FLOW COEFFICIENT - CV - IS BASED ON THE SI-SYSTEM AND IS CALLED THE
FLOW FACTOR - KV
THE FLOW FACTOR - KV - IS DEFINED AS
THE FLOW OF WATER WITH TEMPERATURE RANGING 5 - 30 OC THROUGH A VALVE IN CUBIC METERS PER HOUR (M3/H) WITH A PRESSURE DROP OF 1 BAR
THE FLOW FACTOR IS COMMONLY USED OUTSIDE U.S.
CONVERTING BETWEEN FLOW COEFFICIENT CV AND FLOW FACTOR KV
THE RELATIONSHIP BETWEEN CV AND KV CAN BE EXPRESSED AS:
CV = 1.156 KV
KV = 0.865 CV
PROCEDURE OF THE GATE VALVE PARAMETRIC STUDY:
1. GEOMETRY CHECK AND MODIFICATION USING SPACE CLAIM.
OPEN THE 3D MODEL USING SPACE CLAIM,
THEN EXTEND THE FLANGE SURFACE BY 800 MM BOTH SIDES.
AND LIFT THE SPINDLE AND GATE DISC BY 10 MM INITIALY AND EXTRACT THE VOLUME INSIDE THE GATE VALVE AS SHOWN BELOW.
AND PARAMETRIZE THE LIFT DIMENSION AND UPDATE THE CREATED VOLUME BODY IN CONTEXT. SUPPRESS ALL BODY EXCEPT VOLUME EXTRACTED.
2. MESHING PART: (5.5 MM ELEMENT SIZE WITH CAPTURE CURVATURE)
GENERATE MESH USING THE VALUE BELOW. I ALSO ACTIVATE CAPTURE CURVATURE FOR MORE REFINED IN THE EDGES PORTION.
THEN RENAME THE INLET AND OULET SURFACE.
3. SETUP:
| CASE SET UP | |
| SOLVER TYPE | PRESSURE BASED |
| SOLVER TIME | STEADY STATE |
| GRAVITY | ENABLED |
| VISCOUS MODEL | K-E REALIZABLE |
| MATERIAL | WATER |
| INPUT PARAMETER | LIFT OF GATE VALVE |
| OUTPUT PARAMETER | MASS FLOW RATE AT OUTLET |
| INLET AND OUTLET | PRESSURE BC |
ENABLE THE GRAVITY AND PUT VALUE TO Z.
- CHANGE THE MATERIAL TO H20 AND DELETE THE AIR PROPERTIES.
ENABLE VISCOUS MODEL AND SELECT K-EPSILON AS SHOWN BELOW.
PUT THE VALUE IN INLET PRESSURE OF 10 Pa.
MADE A SURFACE REPORT FOR MASS FLOW RATE IN OUTLET AND PUT IN PARAMETRY TO EASILY CHECK THE RESULT.
SOLUTIONS AND RESULTS:
CASE 1 (LIFT OF 10 MM).
NUMERICAL SOLUTION:
Q = 0.1495 kg/s= 2.370 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 2.370 x √1/0.00145
Cv = 62.245
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 53.842
CONTOUR:
CASE 2 (LIFT OF 20 MM).
NUMERICAL SOLUTION:
Q = 0.2400 kg/s= 3.804 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 3.804 x √1/0.00145
Cv = 62.245
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 53.842
CONTOUR:
CASE 3 ( LIFT OF 30 MM. )
NUMERICAL SOLUTION:
Q = 0.3654 kg/s= 5.792 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 5.792 x √1/0.00145
Cv = 152.086
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 131.555
CONTOUR:
CASE 4 ( LIFT OF 40 MM. )
NUMERICAL SOLUTION:
Q = 0.4808 kg/s= 7.620 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 7.620 x √1/0.00145
Cv = 200.1
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 173.087
CONTOUR:
CASE 5 ( LIFT OF 50 MM. )
NUMERICAL SOLUTION:
Q = 0.5677 kg/s= 8.998 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 8.998 x √1/0.00145
Cv = 236.296
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 204.396
CONTOUR:
CASE 6 ( LIFT OF 60 MM. )
NUMERICAL SOLUTION:
Q = 0.6430 kg/s= 10.191 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 10.191 x √1/0.00145
Cv = 267.616
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 231.488
CONTOUR:
CASE 7 ( LIFT OF 70 MM. )
NUMERICAL SOLUTION:
Q = 0.7237 kg/s= 11.471 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 11.471 x √1/0.00145
Cv = 301,237
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 260.570
CONTOUR:
CASE 8 ( LIFT OF 80 MM. )
NUMERICAL SOLUTION:
Q = 0.7876 kg/s= 12.484 gal/min
SG = 1
△P = 10 pa = 0.00145 psi
Flow Coefficient
Cv = Q x √SG/△P
Cv = 12.484 x √1/0.00145
Cv = 327.834
Flow Factor
Kv = 0.865 x Cv = 0.865 x 57.51
Kv = 283.576
CONTOUR:
RESULTS:
| LIFT | gal/min | Cv | Kv | Iterations |
| 10 | 2.370 | 62.245 | 53.842 | 200 |
| 20 | 3.804 | 99.881 | 86.397 | 200 |
| 30 | 5.792 | 152.086 | 131.555 | 200 |
| 40 | 7.620 | 200.101 | 173.087 | 200 |
| 50 | 8.998 | 236.296 | 204.396 | 200 |
| 60 | 10.191 | 267.616 | 231.488 | 200 |
| 70 | 11.471 | 301.237 | 260.570 | 200 |
| 80 | 12.484 | 327.834 | 283.576 | 200 |
CHART
CONCLUSIONS:
- REFINED MESH HELPS THE CALCULATION MORE ACCURATE.
- THE HIGHER THE LIFT OF GATE DISC, THE HIGHER THE VALUE OF MASS FLOW RATE.
- THERE IS A PRESSURE DROP WHEN LIFT IS HIGHER.
- FROM THE GRAPH, WE CAN SEE THAT THE HIGHER THE LIFT IS THE HIGHER FLOW COEFFICIENT AND FLOW FACTOR HAD OBTAINED.