Gate Valve Parametric Study

Aim:

Perform a parametric study on the gate valve simulation by setting the opening from 10 % to 80%.

• Obtain the mass flow rates at the outlet for each design point.
• Calculate the flow coefficient and flow factor for each opening and plot the graph.
• Discuss the results of the mass flow rate and flow coefficient.

Solution:

Now we will be opening the valve by 10% as shown below using the move command :

Total Height = 290 mm

Therefore 10% = 290*0.1 = 29 mm

Hence it is moved by 29 mm as shown below :

As you can see the valve has opened 10% below:

Fluid Volume Extraction:

Pulled Inlet and outlet

Meshing :

A mesh size of 5 mm was given to the component as shown below :

Flow Coefficient:

When flow goes through a valve or any other restricting device it loses some energy. The flow coefficient is a designing factor which relates head drop (Δh) or pressure drop (ΔP) across the valve with the flow rate (Q).

Q: Flow rate
ΔP: Pressure Drop
Sg: Specific gravity (1 for water)
K: Flow coefficient Kv or Cv

Each valve has its own flow coefficient. This depends on how the valve has been designed to let the flow going through the valve. Therefore, the main differences between different flow coefficients come from the type of valve, and of course the opening position of the valve.

Flow coefficient is important in order to select the best valve for a specific application. If the valve is going to be most of the time opened, probably there should be selected a valve with low head loss in order to save energy. Or if it is needed a control valve, the range of coefficients for the different opening positions of the valve should fit the requirements of the application.At same flow rate, higher flow coefficient means lower drop pressure across the valve.Depending of manufacturer, type of valve, application the flow coefficient can be expressed in several ways. The coefficient can be non-dimensional or with units if parameters such as diameter or density are considered inside the coefficient or just in the equation.

Flow Factor :

A Flow Factor (Kv) is the flow coefficient in metric units that is defined as the flow rate in cubic meters per hour (m3/h) of water at a temperature of 16ºC with a pressure drop across the valve or any other restricting device of 1 bar.

Now we have done a parametric study and varied the valve opening from 10 mm to 80 mm and got the following mass flow rate as shown below:

Now in order to calculate the flow factor we need to find the pressure drop:

1.Valve Opening = 10 mm

Pressure Drop = 15.2 Pascals

SG=1 for water

Q = 0.140 kg/s

K=0.036

Kv=0.50 m3/hr

2.Valve Opening = 20 mm

Pressure Drop = 17.1

K=0.05

Kv=0.79

3.Valve Opening = 30 mm

Pressure Drop = 38.3 Pa

K=0.054

Kv=1.19

4.Valve Opening = 40 mm

Pressure Drop = 32.28

K = 0.078

Kv=1.58

5.Valve Opening = 50 mm

Pressure Drop = 50.6

K=0.078

Kv=2.02

6.Valve Opening = 60 mm

Pressure Drop =79.6 Pa

K = 0.074

Kv=2.38

7.Valve Opening = 70 mm

Pressure Drop =95 Pa

K = 0.078

Kv=2.74

8.Valve Opening = 80 mm

Pressure Drop =99.6 Pa

K = 0.084

Kv=3.17

Conclusion:

As you can see the flow coefficient increases with valve opening