PARAMETRIC ANALYSIS OF GATE VALVE
PARAMETRIC ANALYSIS OF GATE VALVE
Objective: To perform parametric analysis of gate valve for different lifts of gate valve opening.
INTRODUCTION
GATE VALVE
Gate valve, also known as a sluice valve, is a valve that opens by lifting a barrier 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 but are most commonly wedge-shaped.
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 Cv (or flow-capacity rating of valve) can be expressed as:
Cv = `Q√(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).
Flow factor
The metric equivalent flow factor (Kv; commonly used in Europe and Asia) is calculated using metric units:
Kv = `Q√(SG)/(∆P)`
Where,
Kv is the flow factor (expressed in m3.h-1.bar-0.5).
Q is the flow rate (expressed in cubic metres per hour [m3/hr]),
SG is the specific gravity of the fluid (for water = 1),
∆P is the differential pressure across the device (expressed in [bar]).
Kv can be calculated from Cv using the equation
Kv= 0.865. Cv
SETUP
A gate valve is used for passage water which is the fluid used. The lift of 10mm to 80mm is used for calculating and plotting mass flow rate. The Input gauge pressure is 10 Pa and Output gauge pressure is 0 Pa.
Model
The model was imported in Spaceclaim. Model consists of gate disc, bonnet, spindle, wheel, bottom.
Mesh
The model was meshed using ANSYS mesher with element size of 8mm mesh. Elements= 255800 Nodes= 52838.
A mesh metric that identifies elements according to their quality was employed and it can be seen that the elements of lowest quality are minimal. Most of the elements have very high quality in the range of 0.68-1. Hence, the mesh is of acceptable quality. The meshed model is shown in image below.
CASE1
Lift= 10mm.
Convergence
Iteration= 250 were ran and convergence happens at 70 iterations. The residual plot is plotted in ANSYS FLUENT shown below.
Result
Mass flow rate plot
Mass flow rate outlet = -0.14993871 kg/s
Velocity Contour
Velocity cutplane
Velocity of water at the inlet= -0.1415488 m/s
Velocity Streamline
Case 2:
Lift= 20mm
Case 3:
Lift= 30mm
Case 4:
Lift= 40mm
Case 5:
Lift= 50mm
Case 6:
Lift= 60mm
Case 7:
Lift= 70mm
Case 8:
Lift= 80mm
FLOW COEFFICIENT AND FLOW FACTOR
CALCULATIONS
Calculations of Flow Factor
For Lift = 10mm
Q = 0.54 m3/hr
SG = 1, 10-4 bar
Kv = `Q√(SG)/(∆P) = 0.54√1/(10-4)`
KV = 54 m3.h-1.bar-0.5
Calculation of Flow Coefficient
For Lift= 10mm
CV= `K_v/0.865=54/0.865=62.428`
CV= 62.428 US gallons/ min. psi
Similarly, the flow coefficient and flow factor for different lifts are shown below:
|
LIFT(mm) |
FLOW COEFFICIENT(US gallons/ min. psi) |
FLOW FACTOR(m3.h-1.bar-0.5) |
|
10 |
62.428 |
54 |
|
20 |
94.798 |
82 |
|
30 |
141.04 |
122 |
|
40 |
188.902 |
163.4 |
|
50 |
238.15 |
206 |
|
60 |
277.457 |
240 |
|
70 |
314.566 |
272.1 |
|
80 |
347.861 |
300.9 |
Parametric Chart
Conclusion
As the lift of the gate valve increases the mass flow rate also increases. The flow coefficient and flow factor are directly proportional to mass flow rate so it increases with mass flow rate.