Gate Valve Parametric Study

AIM:

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

Objective:

• 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.

GATE Valves:

A gate valve is generally used to completely shut off fluid flow or, in the fully open position, provide full flow in a pipeline. Thus it is used either in the fully closed or fully open positions. A gate valve consists of a valve body, seat and disc, a spindle, gland, and a wheel for operating the valve. The seat and the gate together perform the function of shutting off the flow of fluid.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 .

TYPES OF GATE VALVES:

There are three ways to classify the gate valve.

1. Types of Disk
   1. Solid taper wedge
   2. Flexible wedge
   3. Split wedge or Parallel disks Valve
2. Types of Body Bonnet Joint
   1. Screwed Bonnet
   2. Bolted-Bonnet
   3. Welded-Bonnet
   4. Pressure-Seal Bonnet
3. Types of Stem movement
   1. Rising Stem or OS & Y Type (Outside Stem and Screw Type)
   2. Non-rising Stem type

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. The Kv is related the head drop (Δh) or pressure drop (ΔP) across the valve with the flow rate (Q).

FLOW COEFFICIENT:

Valve Flow Coefficient (Cv) is a valve’s capacity for a liquid or gas to flow through it. It is technically defined as “the volume of water at 60°F (in US gallons) that will flow through a valve per minute with a pressure drop of 1 psi across the valve.”

In simpler terms, the larger the opening in a valve, the larger the Cv. As a valve is opening, the Cv increases until the valve is fully open, where it reaches its highest possible Cv, or 100% open Cv.

Calculating Flow factor and flow coefficient From formula:

Flow factor Kv= Q* ">√(SG/delta P)

Where Q= flow rate

SG= Specific gravity of water=1

Delta P = pressure difference

Flow factor Kv =0.865* Cv

Flow coefficient Cv= Kv/0.865

GEOMENTRY:

Gate Valve:

Geomentric preparation:

By using pull tool extend both sides with 800mm

Volume extract:

Supress all geomentric part except fluid volume.

Meshing:- Mesh size = 10mm

Setup:

• Geomentry - steady solver(pressure based)
• Model- k epsilon realizible with scalable wall functions.
• materials- water(liquid)
• Boundary conditions- inlet pressure =10 pa
• Standard initialization
• number of iterations- 250 iterations

Case 1: lift = 10 mm:

Scalar Residuals:

Contour Velocity :-

Parametric table for mass flow rate :-

Table For Flow rate and flow coefficient:

Dp (mm)	Mass flow rate(Kg/s)	Pressure at Outlet (pa)	Avg velocity at outlet (m/s)	Flow factor	Flow co-efficient
10	-0.14858	0.18342	0	54.31	62.78
20	-0.23686	0.47103	0	88.4	102.2
40	-0.47604	1.87231	0	158.72	183.5
60	-0.65483	3.7775	0	293.30	33.07
80	-0.75008	5.17906	0	408.36	472.0

Conclusion:

• Parametric study of a system helps in drastically decreasing the simulation time taken to perform simulation on each parameter.
• From the above results, it can be said that, with the increase in the gate valve lift the mass flow rate also increases.
• Parametric study is time reducing option when studying the effects of changes of certain parameters on a system.
• Flow co-efficient also helps in computing efficiency of the system and effect of pressure on the system.