Gate Valve Parametric Study

                                                               PARAMETRIC STUDY ON GATE VALVE

 

Aim

• To obtain the mass flow rate at the output for each design point
• To calculate Flow coefficcient and Flow factor for each opening and to plot it in the graph

 

Introduction

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 but are most commonly wedge-shaped (in order to be able to apply pressure on the sealing surface).

Gate valves work by inserting a rectangular gate or wedge into the path of a flowing fluid. They are operated by a threaded stem which connects the actuator (generally a hand wheel or motor) to the stem of the gate.

Bonnets provide leakproof closure for the valve body. 

 

Theory

One reason that gate valves are not normally used to regulate flow is that the flow rate of the fluid is not proportional to the amount that the valve is open. Moreover, a partially open gate valve may suffer from vibration in which the valve may move from its assigned position. Also the gate and seat may be subject to excessive wear if the valve is partially open.

One reason that gate valves are not normally used to regulate flow is that the flow rate of the fluid is not proportional to the amount that the valve is open. Moreover, a partially open gate valve may suffer from vibration in which the valve may move from its assigned position. Also the gate and seat may be subject to excessive wear if the valve is partially open.Gate valves are generally not suitable for regulating flow or pressure or operating in a partially open condition. For this service, a plug valve or a control valve should be used. It must be noted that because of the type of construction a gate valve requires many turns of the hand wheel to completely open or close the valve. When fully opened, gate valves offer little resistance to flow and its equivalent length to diameter ratio (L/D) is approximately 8.

                                                                                             

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).

in our experiment the pressure drop across the valve is 10pa

as 1 kg/s =15.85 gal/min the conversion will be easier

         

for example 0.1489 kg/s to gal/min=0.1489*15.85=2.36 gal/min

 

For Flow Factor

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

where

K_v is the flow factor .

Q is the flowrate (expressed in cubic metres per hour []),

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

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

As K_v can be calculated from C_v using the equation:

 

Sectional view of 10mm lift :

10 mm lift with enclosed volume

 

                  

 

 inlet and Outlet:

                       

 

 

Meshed Geometry:With 190312 mesh elements

         

 

                                                     

Turbulance model used: k-epsilon Realizable model with enhanced wall fucnction

Boundary conditions:pressure inlet10 pa

 

 

Results:

DP0:10mmlift:

veloity contour

mass flow rate 

outlet -0.14896615 kg/s

                       

note:The DP7 value Shown at positio10 is incorrect ,a mistake made by Ansys.Re-Running the solution Provided the value of -0.8208 kg/s.

 

 DP 1:(20mm)

 

 

Velocity Contour:

 

Animation file:

 

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

 

 

 

 

DP 2 :(30mm)

 

Velocity Contour:

 

Animation Files:

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

 

 

 

 

 

DP3:(40mm)

Velocity Contour:

 

 Animation Files:

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

 

 

 

DP4:(50mm)

 

Velocity Contour:

Animation FIles:

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

 

 

DP5:(60mm)

velocity Contour:

Animation Files:

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

 

 

DP6:(70mm)

 

Velocity Contour:

Animation Files:

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

 

DP7:(80mm)

Velocity Contour Plot

 

Animation FIles:

https://drive.google.com/drive/u/1/folders/11emehpSxrgpxuqe7cneQUWsGUq5zdlfG

 

Conclusion:

(Jupiter-Python 3 code)

Note :the negative sign doesn't implies the flow rate is decreasing,this is because of sign conversion with x ,y and z axis of the geometry.i.e the inlet has +ve flow rate while outlet has -ve.

Plot 1)Outlet Flow v/s Lift

            

 

plot2 (Flow coefficient and Flow factor v/s lift)

 

           

         

  Plot 3:massflowrate v/s Flow coefficient

    

           

From the graphs we can conclude that:

• as the lift increases massflow rate increases
• Mass flow rate and flow coefficient are directlty proportional i.e they varies linearly
• Flow factor=0.865* Flow Coefficient

 

 

References:

https://www.sciencedirect.com/topics/engineering/gate-valve

https://en.wikipedia.org/wiki/Gate_valve

https://en.wikipedia.org/wiki/Flow_coefficient