Week 9 - Parametric study on Gate valve.

Gate valve :

A gate valve can be defined as a type of valve that uses a gate or wedge type disk,and the disk moves perpendicular to flow

to start or stop the fluid flow in piping .A gate valve is the most common type of valve used in any process plant .It is a linear

motion valve used to start or stop fluid flow.

 

Applications :

Socket or butt-welding end-gate valves in air, fuel gas, feedwater, steam, lube oil, and other systems are typical applications.

Threaded-end gate valves may be used in air, gaseous, or liquid systems.

Concern for leakage from threaded connection can be addressed by seal welding the threaded connection or by using thread

sealants, as appropriate. In low-pressure and low-temperature systems such as fire protection systems’ water piping or water

distribution pipelines, flanged gate valves are commonly used.

Step 1) Geometry:

We load the gate valve step file in space claim. extract the fluid volume by selecting the proper edges.

We extend the fluid flow region go to design > pull > drag the inlet and outlet by 0.8m 

We parametrise the lift go to design > move > select the gate disc > and move this component along Z direction give the

value 0.010m ie 10mm and go to the groups option and create parameter then the group 1 is created in this we can put the

value manually to change it.

Section view along the YZ palne of geometry: (10mm lift)

Extracted fluid volume:

Step 2) Meshing :

We use element size =7mm

 

Give a name to inlet and outlet boundary

Elemental quality:

Step 3 ) Set up and solution :

Viscous model:

Material:

Cell zone condition:

Boundary conditions :

Solution method :

Solution initialization : Hybrid 

 

 The velocity at inlet is 0.1415488 m/sec . The Reynolds number is calculated using the formula:

$R_e=\frac{\rho .V.D}{\mu }$

  $\to$

      (1)

In this case:

$\rho$

=998.2 $\frac{kg}{m^3}$

 

D=0.1 m

V=0.1415488 m/sec

$\mu$

=0.001003 kg/m.s

Put all this value in eq (1) so $R_e$

=14087.13 

The Reynolds number obtained is greater than 2000 hence the flow is turbulent and we choose k-$\epsilon$

viscous model.

 Create a mass flow rate report :

Create a pressure at inlet report :

Create a pressure at outlet report :

 

Create a YZ plane along geometry for velocity contour :

We run the simulation for 250 iterations :

Step 4) Results :

Case 1) 10 mm lift 

Residual plot:

solution is converged in 51 iterations :

 Mass flow rate plot:

Pressure at inlet plot:

Pressure at outlet plot:

Velocity contour plot:

Pressure plot:

Velocity Vector plot:

 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 $C_v$

can be expressed as :

$\to$

     (1) 

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 ($K_v$) :

                               The flow of water with temperature ranging 5-30*C  through a valve in cubic meters per hour ($\frac{m^3}{h}$

) with a pressure drop of 1 bar .

The relationship  between flow coefficient and flow factor can  be expressed as :

$K_v$=$0.865C_v$    $\to$

  

(2)  We calculate the flow coefficient and flow Factor for 10 mm lift 

mass flow rate = 0.1449 kg/sec , 1kg/sec=15.85 gal/min ,   Q=2.2966 gal/min

SG (specific gravity) for water  =1 

 ΔP = Pressure at inlet - pressure at outlet = 9.827pa ,      1pa =0.000145psi  

 ΔP =0.00142 psi 

 Put this values in eq (1) 

$C_v$= 60.9454 

put this value in eq (2) we get

$K_v$=52.7177

 

Case 2) 20 mm lift 

Residual plot:

Mass flow rate plot:

Pressure at inlet plot:

Pressure at outlet plot:

Velocity contour plot:

Pressure plot:

Velocity vector plot:

 We calculate the flow coefficient and flow Factor for 20 mm lift 

mass flow rate = 0.2256 kg/sec , 1kg/sec=15.85 gal/min ,   Q=3.5757 gal/min

SG (specific gravity) for water = 1 

 ΔP =9.5800 pa ,      1pa =0.000145psi  

 ΔP =0.00138 psi 

   Put this values in eq (1) 

$C_v$=96.2542

put this value in eq (2) we get

$K_v$

= 83.2598

 Case 3) 30 mm lift :

Residual plot:

Mass flow rate report plot :

Pressure at inlet plot:

Pressure at outlet plot:

Velocity contour plot :

Pressure plot :

Velocity vector plot:

 We calculate the flow coefficient and flow Factor for 30 mm lift 

mass flow rate = 0.3379 kg/sec , 1kg/sec=15.85 gal/min ,   Q=5.3557 gal/min

SG (specific gravity) for water  =1 

 ΔP = Pressure at inlet - pressure at outlet = 9.0605pa ,      1pa =0.000145psi  

 ΔP =0.00131 psi 

  Put this values in eq (1) 

$C_v$

=147.9720

Put this value in eq (2) we get 

$K_v$

= 127.9957

Case 4) 40 mm lift 

Geometry:

Residual plot:

Mass flow rate report :

Pressure at inlet plot :

Pressure at outlet plot :

Velocity contour plot:

Pressure plot:

Velocity vector plot:

 We calculate the flow coefficient and flow Factor for 40 mm lift 

mass flow rate = 0.3957 kg/sec , 1kg/sec=15.85 gal/min ,   Q=6.2718 gal/min

SG (specific gravity) for water  =1 

 ΔP = Pressure at inlet - pressure at outlet = 8.7734 pa ,      1pa =0.000145psi  

 ΔP =0.00127 psi 

  Put this values in eq (1) 

$C_v$=175.9909

 Put this value in eq (2) we get 

$K_v$=152.2321

Case 5) 50mm  lift :

Geometry:

Residual plot:

Mass flow rate report plot:

Pressure at inlet plot:

Pressure at outlet plot:

Velocity contour plot:

Pressure plot:

Velocity vector plot:

We calculate the flow coefficient and flow Factor for 50 mm lift 

mass flow rate = 0.5480 kg/sec , 1kg/sec=15.85 gal/min ,   Q=8.6858 gal/min

SG (specific gravity) for water  =1 

 ΔP = Pressure at inlet - pressure at outlet = 7.5182 pa ,      1pa =0.000145psi  

 ΔP =0.00109 psi 

  Put this values in eq (1) 

$C_v$= 263.0852 

Put this value in eq (2) we get 

$K_v$=227.5686

Case 6) 60mm  lift :

Geometry :

Residual plot:

Mass flow rate plot:

Pressure at inlet plot:

Pressure at outlet plot:

Velocity contour plot:

Velocity vector plot:

We calculate the flow coefficient and flow Factor for 60 mm lift 

mass flow rate = 0.6485 kg/sec , 1kg/sec=15.85 gal/min ,   Q=10.2787 gal/min

SG (specific gravity) for water  =1 

 ΔP = Pressure at inlet - pressure at outlet = 6.5367 pa ,      1pa =0.000145psi  

 ΔP =0.00094 psi 

  Put this values in eq (1) 

$C_v$=335.2542

Put this value in eq (2) we get ,

$K_v$=289.9948

The result table of a parametric study with different lift is shown below:

Sr No	Gate Disc Lift in (mm)	Flow coefficient	Flow factor
1	10	60.9454	52.7177
2	20	96.2542	83.2598
3	30	147.972	127.9957
4	40	175.9909	152.2321
5	50	263.0852	227.5686
6	60	335.2542	289.9948

The graph of Gate disc lift vs flow coefficient is shown below:

The graph of Gate disc lift vs flow factor is shown below:

 Result Discussion :

From the observation of result table we can say that the mass flow rate is increases when we increase the gate disc lift of

gate valve.

The pressure drop is also decreases  when we increase the gate disc lift of gate valve.

The negative sign of the mass flow rate value is due to the mass flow which is leaving at the outlet.

The flow coefficient is also increases when we increase the  gate disc lift of gate valve.

The flow factor is also increases when we increase the  gate disc lift of gate valve.

Conclusion:

The mass flow rate is increases if we increase the gate valve opening (gate disc lift) .

The velocity of the flow is also increases when we increase the gate disc lift of gate valve.

The pressure drop is decreases when we increase the gate disc lift of gate valve.

The graph of flow factor and flow coefficient with respect to lift of the gate valve is plotted.

The gate valve opening is increases then flow coefficient and flow factor is also increases.

The design point 70mm and 80 mm is not calculated because result obtained is not accurate.the reason behind that is the

bug in ansys student version.