PARAMETRIC STUDY OF GATE VALVE

AIM:

Parametric study on the gate valve simulation by setting the opening from 10 % to 80% of gate valve.

OBJECTIVE:

1. Obtaining the mass flow rates at the outlet for each design point.
2. Calculating the flow coefficient and flow factor for each opening and plotting the graph.

GATE VALVE:

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 (used in this simulation) 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 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.

Gate valves are typically constructed from cast iron, cast carbon steel, ductile iron, gunmetal, stainless steel, alloy steels, and forged steels.

Bonnets provide leakproof closure for the valve body. Gate valves may have a screw-in, union, or bolted bonnet. A screw-in bonnet is the simplest, offering a durable, pressure-tight seal. A union bonnet is suitable for applications requiring frequent inspection and cleaning. It also gives the body added strength. A bolted bonnet is used for larger valves and higher-pressure applications.

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:

C_V = `Q*sqrt((SG)/(△P))`

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).

In more practical terms, the flow coefficient Cv is the volume (in US gallons) of water at 60 °F that will flow per minute through a valve with a pressure drop of 1 psi across the valve.

FLOW FACTOR:

The metric equivalent flow factor (K_V; commonly used in Europe and Asia) is calculated using metric units:

K_V = `Q*sqrt((SG)/(△P))`

Where,

Kv is the flow factor (expressed in m³.h^-1.bar^-0.5)

Q is the flowrate (expressed in cubic metres per hour m³/h)

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

∆P is the differential pressure across the device (expressed in [bar]).

C_v can be calculated from K_v using the equation:

C_V = 1.156 × K_V

MODEL 4" GATE VALVE:

FLOW DOMAIN:

Maximum Possible lift of the Gate Disc

The gate disc lift value is set as a parameter (GROUP 1)

BOUNDARIES:

MESH:

Body sizing applied for a finer mesh on the fluid volume.

STEADT-STATE SIMULATION SETUP:

Fluid Material (Inside Gate valve; Fluid Volume) -> Water Liquid (Properties Below)

Re_d = `(ρ×V×D)/(µ)`

ρ `->` Density of Water = 998.2 kg/m³

D `->` Diameter of the pipe at inlet or outlet = 100 mm = 0.1 m

V `->` Velocity of fluid = 0.1415488 m/s

µ `->` Viscosity of water = 0.001003 kg/m-s

Re_d = `(998.2×0.1415488×0.1)/(0.001003)` = 14087.139

Re_d > 2500, Hence the flow is turbulent. So, K-epsilon Realizable Model with scalable wall functions.

Pressure-Based Solver

Pressure-Velocity Coupling `->` Coupled

Spatial Discretization

Pressure `->` Second Order

Momentum `->` Second Order Upwind

Flux Report `->` Mass Flow Rate `->` OUTLET `->` Creating an Output Parameter

BOUNDARY CONDITIONS:

INLET `->` Pressure (Gauge) = 10 Pa

OUTLET `->` Pressure (Gauge) = 0 Pa

Standard Initialization from INLET

Number of Iterations Given to Run = 300

OBSERVATIONS OF PARAMETRIC SIMULATIONS:

10% RISE OF GATE DISC = 11 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.15511 kg/s (-ve sign indicates fluid flows out of volume) = 0.558396 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*0.558396`

K_V = 55.8396 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*55.8396` = 64.550776 GPM.Psi^-0.5

20% RISE OF GATE DISC = 22 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.26186 kg/s (-ve sign indicates fluid flows out of volume) = 0.942696 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*0.942696`

K_V = 94.2696 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*94.2696` = 108.9756576 GPM.Psi^-0.5

30% RISE OF GATE DISC = 33 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.39627 kg/s (-ve sign indicates fluid flows out of volume) = 1.426572 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*1.426572`

K_V = 142.6572 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*142.6572` = 164.9117232 GPM.Psi^-0.5

40% RISE OF GATE DISC = 44 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.50337 kg/s (-ve sign indicates fluid flows out of volume) = 1.812132 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*1.812132`

K_V = 181.2132 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*181.2132` = 209.4824592 GPM.Psi^-0.5

50% RISE OF GATE DISC = 55 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.5943 kg/s (-ve sign indicates fluid flows out of volume) = 2.139480 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*2.139480`

K_V = 213.9480 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*213.9480` = 247.323888 GPM.Psi^-0.5

60% RISE OF GATE DISC = 66 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.67686 kg/s (-ve sign indicates fluid flows out of volume) = 2.436696 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*2.436696`

K_V = 243.6696 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*243.6696` = 281.6820576 GPM.Psi^-0.5

70% RISE OF GATE DISC = 77 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.7331 kg/s (-ve sign indicates fluid flows out of volume) = 2.639160 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*2.639160`

K_V = 263.9160 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*263.9160` = 305.086896 GPM.Psi^-0.5

80% RISE OF GATE DISC = 88 mm

△P `->` Pressure Difference = 10 - 0 = 10 Pa = 10^-4 Bar

SG `->` Specific Gravity of the Fluid (SG_Water = 1)

Q `->` Flowrate = -0.83977 kg/s (-ve sign indicates fluid flows out of volume) = 3.023172 m³/h

K_V = `Q*sqrt((SG)/(△P))` = `Q*sqrt(1/10^-4)` = `100*Q` = `100*3.023172`

K_V = 302.3172 m³.h^-1.bar^-0.5

C_V = 1.156 × K_V = `1.156*302.3172` = 349.4786832 GPM.Psi^-0.5

OBSERVATIONS:

Rise of Gate Disc (%)	Rise of Gate Disc (mm)	Pressure Difference (Inlet – Outlet) (Pa)	Mass Flow Rate at Outlet (kg/s)	Flow Coefficient, CV (GPM.Psi-0.5)	Flow Factor, KV (m3.h-1.bar-0.5)
10	11	10	0.15511	64.550776	55.8396
20	22	10	0.26186	108.975657622	94.2696
30	33	10	0.39627	164.9117232	142.6572
40	44	10	0.50337	209.482459244	181.2132
50	55	10	0.5943	247.323888	213.9480
60	66	10	0.67686	281.6820576	243.6696
70	77	10	0.7331	305.086896	263.9160
80	88	10	0.83977	349.4786832	302.3172

INFERENCE:

Mass flow rate increases as the gate disc rises.

Flow coefficient increases as the gate disc rises.

Flow factor increases as the gate disc rises.

CONCLUSION:

• Mass flow rate at the outlet, flow coeffiicient and flow factor increases with the opening of the gate valve from 10% to 80%.
• This increase in mass flow rate at outlet, flow coefficient and flow factor are gradual and the varration is proportional.
• The variation of mass flow rate at outlet, flow coeffcient and flow factor are linear with respect to the gate valve opening, with the varration from 70% to 80% is more signficant than the rest.
• For selecting a gate valve based on calculated values of Flow coefficient (C_V) or Flow factor (K_V), the value should lie between 20% and 80% gate valve opening. Here, this gate valve (100 mm or 4 inch) is optimum for conditions with C_V ranging from 108.975 to 349.478 and (K_V) ranging from 94.26 to 302.31.