Week 9 - Parametric study on Gate valve.

                                                                                                AIM 

    To perform a parametric study on the gate valve simulation by setting the opening from 10 % to 80% and obtain the mass flow rates at the outlet for each design, calculate the flow coefficient and flow factor for each case and discuss the variation of the mass flow rate and flow coefficient for various lifts of the gate.

                                                                                   INTRODUCTION 

    The parameter that is varied in this simulation is the lift of the gate and the reason we parameterize this lift is to study its effect on the mass flow rate, flow coefficient, etc. Also we know that on lifting the gate, the flow rate increases as more fluid rushes through the gate. But this simulation is performed to validate the numerical results of the ANSYS FLUENT.

Flow Coefficient - C_v

The flow coefficient - C_v - is based on the imperial units system and is defined as:

• the flow of water through a valve at 60 ^oF in US gallon/minute at a pressure drop of 1 lb/in²

The flow coefficient is commonly used in the U.S.

Flow Factor - K_v

The metric equivalent of the flow coefficient - C_v - is based on the SI-system and is called the

• Flow Factor - K_v

The flow factor - K_v - is defined as

• the flow of water with temperature ranging 5 - 30 ^oC through a valve in cubic meters per hour (m³/h) with a pressure drop of 1 bar

The flow factor is commonly used outside U.S.

The relationship between C_v and K_v can be expressed as:

• C_v = 1.16 K_v                            (1)
• K_v = 0.862 C_v                          (2)

    We perform meshing in the ANSYS MESHING using a mesh size of 7 mm and name the inlet and outlet.

    We use steady state, pressure based solver since we are interested in the end results and since the fluid is liquid which is incompressible and by enabling the gravity, we set the physics for the model. Here we have used the k-epsilon realizable model with enhanced wall functions. The fluid domian material is the water-liquid. Boundary conditions are pressure inlet of 10 Pa (gauge) and pressure outlet of 0 Pa. Hybrid initialization is used for this simulation and the mass flow rate is calculated for 150 iterations.

                                                                                       RESULTS 

Mass flow rate (Q) is in metric units i.e, m3/h, pressure difference in Bar

Velocity contour plots for various lifts 

Lift = 10 mm                                                                                                              Lift = 20 mm

Mass flow rate = -0.5	Mass flow rate = -0.79
Flow factor = 50	Flow factor = 78.9
Flow coefficient = 57.7	Flow coefficient = 91.3

Lift = 30 mm                                                          Lift = 40 mm

Mass flow rate = -1.18	Mass flow rate = -1.36
Flow factor = 117.9	Flow factor = 139.9
Flow coefficient = 136.4	Flow coefficient = 157.2

Lift = 50 mm                                                          Lift = 60 mm

Mass flow rate = -1.9	Mass flow rate = -2.12
Flow factor = 189.9	Flow factor = 212
Flow coefficient = 219.6	Flow coefficient = 245

Lift = 70 mm                                                          Lift = 80 mm

Mass flow rate = -2.45	Mass flow rate = -2.66
Flow factor = 245.9	Flow factor = 266.9
Flow coefficient = 283.2	Flow coefficient = 307.5

                                                                                  CONCLUSION 

    On lifting the gate gradually by 10 mm, the mass flow rate increases gradually as expected and so does the velocity, flow factor and the flow coefficient.