'Control_Valve' simulation project by jshanthi


#1

I created a new simulation project called 'Control_Valve':

Thermo-Mechanical analysis of a control valve.


More of my public projects can be found here.


#2

A valve is a mechanical device that controls the flow of fluid and pressure within a system or process. Control valves are widely used in power plants to control all thermal processes; they are very important and accountable pieces of power plants equipment. The designation control valve may be confusing because all valves perform a fluid control function. In the valve industry, however, the term has a specific meaning. As defined by the Instrument Society of America (ISA) S51.1, a control valve is “a final controlling element, through which a fluid passes, which adjusts the size of flow passage as directed by a signal from a controller to modify the rate of flow of the fluid”. Control valves are used whenever it is necessary to continuously and accurately regulate the flow rate of a fluid. The possible choices for control and regulating service are globe valves, butterfly valves, ball valves and plug valves.

The control valve used here has is a diverting type control valve. It has one inlet along with two outlets. The inlet is named as AB while the outlet is designated as A and B. The port B is closed by the screw action of a spindle using hand wheel. The schematic diagram of the valve is shown in the figure 1. In this project, the thermo-mechanical analysis of a control valve is performed with transient temperature being considered, in order to study its effects during Heat-up and Cool-down transient.

Due to symmetry, only half of the geometry is considered for the analysis. The geometry of the control valve used for the analysis is shown below,

The geometry of the valve was meshed using Fully Automatic Tetrahedralization with fine mesh being chosen. The meshed model is shown below,

Uncoupled thermo-mechanical analysis-Advanced (i.e. transient, static and non-linear) was selected as an analysis type in this project. The material used is steel. The initial conditions were defined. Now, the boundary conditions needed to be defined. The inlet and open end of the one outlet nozzle were constrained via remote displacement boundary condition. The symmetric boundary condition was applied to the symmetric side. The face set “Loads_Applied” was selected at which the thermal and mechanical loads were applied. In case of the loads to be applied, there are two cases involved. First being, Heat-up transient where the temperature rises from 307.15 K to 573.15K within 10 seconds and then it is kept constant in order to attain homogeneous distribution. Second case is where the temperature falls down from 573.15K to 307.15K within 10 seconds and then it is kept constant in order to attain thermal equilibrium. The face set “Heat_Fluxes” was selected and the convection film co-efficient of 20 W/m2K was applied to this face set. The analysis ran for 470 seconds on 32 core machine and took around 238 min. to complete. The results are presented below,

Heat-up Transient:

Temperature Distribution for Heat-up Transient at t = 15 seconds

Cauchy Stress at Heat-up Transient

Von-mises Stress at Heat-up Transient

Cool-down Transient:

Temperature Distribution for Cool-down Transient at t = 240 seconds

Cauchy Stress at Cool-down Transient

Von-mises Stress at Cool-down Transient

Conclusion:

From the figure, it can be clearly seen that the higher stresses can be avoided by introducing the seat ring. Moreover, the critical parameters such as internal radii and the wall thickness of the valve can be modified in order to minimize the stresses. The suitable film co-efficient is needed to be selected in order to obtain lower stress.[quote=“jshanthi, post:1, topic:9952, full:true”]

I created a new simulation project called 'Control_Valve':

Thermo-Mechanical analysis of a control valve.


More of my public projects can be found here. [/quote]