Natural Convection-II for a low voltage control panel using Ansys-Icepak

Aim :

The aim of this challenge is to check the temperature increases in the configuration of the low voltage control panel with circuit breakers and bus bars. The impact of natural convection on circuit breakers and bus bars device was also observed.

Problem Description:

The system of bus bars and disrupting circuits has been designed to study the natural convection effect and heat loss at a low voltage panel.

For that, build the enclosure with Panel dimensions:

height-2000mm

width-800 mm

depth-900mm

Choosing the height of the cabinet here is a rather tough thing. We must select a size in order for the airflow to circulate equally and systematically in the cabinet.

Using mesh assemblies separately gives us the non-conformal mesh.

Now, address the normal convection issue by preserving the surface region of the radiation.

Introduction:

A low-voltage panel is a part of a power distribution system which divides the power supply into branch circuits by supplying each circuit with a protective disruptor or fuse in a shared enclosure.

Panelboards are used primarily to safeguard against electrical surges and short circuits while distributing power across a building or installation.

Circuit Breaker:

A circuit breaker is an electric switch that is operated automatically to protect a circuit against damage from overload or shortening by excessive current. The basic task is to stop the current flow following the discovery of a fault. In contrast, a circuit breaker can be reset to resume normal operation manually or automatically, in order to replace a fuse that works occasionally.

Circuit breakers are manufactured of various types, from tiny gadgets to protect low-current circuitry or home electronics to massive switchgear to protect high-voltage circuits to power the whole community. As an automatic method for removal of control from a disabled device, the common role of a circuit breaker or fuse is sometimes abbreviated in an OCPD type.

Types of circuit breakers are:

• Low-voltage
• Solid-state
• Magnetic-state
• Thermal-magnetic
• Magnetic-Hydraulic, etc.

Bus bars:

With greater simplicity and versatility than any other permanent construction and storage formes, Busbars deliver energy. Sometimes spelled bus bars or bus bars are metal strips of copper, brass, or aluminum, which both use electricity and drive.

Busbar comes in red, rectangular, cross-sectional, and a number of other forms. The rectangular bus bar is primarily used in the control network. A wide range of busbar arrangements is typically made from copper, aluminum, and brass.

Geometry:

Using the Icepak, we have created a geometry of the enclosure with the dimensions of

height-2000mm

width-800 mm

depth-900mm.

By trial and error, the size of the cabinet is set to the dimensions of 2000 * 2800 * 1500 mm

To the package, we put a few grills, from which the air is pumped inside the package and leaves another flame. The effect is that air rotates inside the cabinet as the circuit breakers heat the bus bars.

We have to direct the air in both grids, which must be circulated indoors. The features of the air-sucking grid

The upper grid is set to normal, so the air flowing through this grille went outside.

The geometry layout:

Here we created a box geometry that contains block circuit breakers, bus bars are connected to the blocks.

Dimensions and power in watts for the bus bars, circuit breakers are provided in the challenge.

Check that there are no gaps in the connections between the bus bars and the circuit breakers. The solution will diverge if some gulf exists between the two components.

Meshing:

We have toggled the mesh assemblies separately in the mesh control to obtain the non-conformal networking.

A non-conformal network, whether the nodes at the device suit slightly or none. That means that, on one side of the interface, one, few, or every node has no match on the other. Calculations for non-conformal interfaces are done using a simulated polygon system that stores the vector and centroid areas of the polygon faces.

There is no movement in the node and cells are not necessarily waterproof cells. The gradients are therefore adjusted to take the missing face area into account.

Here we have generated a non-conformal mesh with the number of elements are 2341694 and the number of nodes is 2398982.

Slack values can be defined in such a way that the cells on each side of the interface are either fluid or rigid, of the same content, and should not break any of the "Non-Conformal Assembly Laws" set out in the connection.

Meshing for the total domain with cabinet:

Meshing for the electronic panel board:

Skewness:

Skewness is the disparity between the shape of the cell and the type of an equilateral volume unit. The general concept is that with certain fluxes, the maximal skewness will be held below 0.95, with an average of less than 0.392 for a three-wing / tetrahedral mesh.

In this case, we achieved the good skewness value regarding the mesh quality.

Numerical setting:

Basic parameters:

n the Basic parameters, we have considered the flow, and radiation was turned on and the flow region was considered to be Turbulent.

• To capture the natural convection phenomena in the problem, it necessary to toggle the radiation option and then toggle surface to surface radiation model.
• A turbulent flow regime has to be calculated with the gravity vector of -9.81 m/s in Y-direction in the natural convection space.
• The initial temperature for the case is set to 25 deg centigrade

Basic settings:

Set no of iterations 100 and convergence criteria for energy to 1e-12.

The total number of iteration was set to be 100 iterations and coming to the convergence criteria the flow was set to 0.0001 and energy was 1e-12, and the turbulent kinetic energy and turbulent dissipation rate were 0.001

From the residual plot, it is clear that the simulation has reached the converged stage and also obtained the converge, and they are no fluctuations in the plot.

Parallel settings:

Here we have to use the parallel option and given the six processors because my PC supports till this point. We can increase or decrease the number of processors as per they are suitable in the PC.

Temperature Linear solver: F cycle is selected for Type Enter 1e-6 for both the Termination criterion and Residual reduction tolerance

In applied mathematics, discretization is the process of transferring continuous functions, models, variables, and equations into discrete counterparts. This process is usually carried out as a first step toward making them suitable for numerical evaluation and implementation on digital computers.

The discretization scheme properties were set accordingly as shown below

Enter a value of 1e-6 for both the Termination criterion and Residual reduction tolerance and the F cycle is was selected.

Select Double for the solver Precision.

Single precision means that the floating-point numbers will be represented in a 32-bit system whereas double-precision means that they will be represented in a 64-bit system. So Calculation in double precision will be more accurate.

Save the model:

ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) as well. If we exit ANSYS Icepak before you start the calculation, we will be able to open the job that we saved and continue with our analysis. If we start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your job file when it saves the model.

Solve the model.

There are no universal metrics for judging convergence, a good indicator is when the solution no longer changes with more iterations, and when the residuals have decreased to a certain degree. The default criterion is that each residual will be reduced to a value of less than 10^-3 except the energy residual, for which the default criterion is 10^-7. It is a good idea to judge convergence not only by examining residuals levels but also by monitoring relevant integrated quantities.

ANSYS Icepak will begin to calculate a solution for the model, and a separate window will open where the solver will print the numerical values of the residuals. ANSYS Icepak will also open the Solution residuals graphics display and control window, where it will display the convergence history for the calculation.

Examine and post-process the results:

Natural convection inside enclosures:

Natural convection in enclosures, also known as internal convection, takes place in rooms and buildings, in furnaces, in cooling towers, and in electronic cooling systems.

External natural convection varies from external convection where the heated or cooled wall is in contact with the quiescent fluid and the boundary layer may be formed without any constraint. Internal convection usually cannot be treated using simple boundary layer theory because the entire fluid in the enclosure engages to the convection.

Temperature:

1. Filled colors, give a good visualization for the temperature, pressure, and mass flow rate, etc.
2. The color legends are used to show the temperature contour.

Temperature Contour:

Joule heating explains how the energy of an electric current is converted into electricity when it flows through a barrier. This is often called resistive or ohmic heating. In specific, electric energy is transferred to heat by resistive losses in the substrate as the electric current passes through a solid or liquid with minimal conductive capacity.

When the conduction electrons transfer energy to the conductor's atoms via collisions the heat is generated on the microscale. It also ensures that the power produced by the circuit breakers would reduce the current-carrying ability as the conductor duration decreases, regardless of the resistance of the components.

The thermal flow of components decreases slightly as the driver length increases due to the above statement.

In the above contour, we have seen that the max. temperature is 43.58 deg and min. the temperature is 25.00 deg.

The object face of the components gives us a more detailed view compare to the cut plane

Temperature animation:

Velocity:

Ascertain grids have been developed, the air movement has only taken place in the enclosure via such grids. We kept the free area ratio to 0.5 a non-dimensional number in order to circulate the air inside the frame.

The natural convection phenomena happen inside the cabin is due to the air circulated over the heated bus bars and circuit breakers.

The velocity in the enclosure is built up to 15.50 m/s. The max velocity is attained inside the enclosure.

The trace of the particle tells us clearly whether or not the flow originates from the grill on the side and leaves the grill.

Animation for the velocity:

We can clearly see hear that the flow is coming inside from the downside grill and leaving from the upper grill. This tells us the physics we have set for the problem is correct.

The velocities at the entry and exit points of the enclosure are

The velocity of air going inside the grille through the grille.3 is 8.07 m/s and the air going out through the grille.3 with the velocity of 6.54 m/s.

And for other items such as block, circuit breakers, and bus bars the speed is 0 m / s, as they are not active

Speed particle trace animation:

Summary report:

A summary report is a short, written communication that may have a variety of purposes, such as: To brief the reader on the details of a particular event. To analyze a particular issue, draw conclusions, and make recommendations.

Go to report -> summary report -> Select the object -> select the value (temp, speed, heaty flow, etc.) -> Write.

Temperature:

It gives us the max temperature and min temperature of the objects we have selected collectively.

The mean temperature, standard difference, and area/volume ratio info, which can be used for comparing the effects, can also be obtained here.

Velocity:

Above in the velocity section, we have seen that the max. the velocity recorded as 15.50 m/s.

But here in the report, it shows the max.velocity of 8.99 m/s.

As it only displays the speeds registered on the grids in the above article. However, our maximum speed is recorded in the box which is not included in the study.

Heat Flow:

Heat can flow from one place to another, just like all kinds of energy. Heat flows through the conduction of solids, where two objects in contact with each other transfer heat between them. This happens because the molecules hit each other, and the faster-moving molecules in the hot object spread that energy to the cooler object.

• That happens because the molecules hit each other, and the faster-moving molecules in the hot object spread that energy into the cooler object.
• Here if we see the total heat loss or heat flow of the circuit breakers, it is 442 W manually (means the input), coming to the simulation it is 450 W. Which is matched up to 95%.
• This can be another proof that our simulation is gets converged and throws the correct values as outputs.

Heat transfer coefficient:

It is used in calculating the heat transfer, typically by convection. The heat transfer coefficient has SI units in watts per squared meter kelvin: W/(m²K). The heat transfer coefficient is the heat transferred per unit area per kelvin. Thus the area is included in the equation as it represents the area over which the transfer of heat takes place. The areas for each flow will be different as they represent the contact area for each fluid side.

The max heat transfer coefficient recorded on selected objects is 63.76 W/K-m2.

Conclusion:

From this challenge, we can conclude that there is an increase in temperature for the low voltage control panel for the configuration in a statement.