Transformer Room Ventilation CFD Simulation, ANSYS Fluent Training

Project Description

The present problem simulates the air conditioning inside a room where the transformers are located using ANSYS Fluent software. Transformers are basically devices that can transfer electrical energy between two or more windings through electromagnetic induction, and as a result, a variable current in the primary winding of the transformer generates a variable magnetic field, which leads to the voltage production in the secondary winding. These transformers are placed in a room due to safety issues, in which an optimal air conditioning system should be used where the transformers are stored. In fact, these transformers are considered as a kind of heat source that affect the ambient air temperature.

In this project, a two-piece room is designed with a divider in the middle, made by wooden wall with a thermal conductivity of 0.173 W.m-1.K-1. Inside the room, there are three transformers made of aluminum with a thermal conductivity of 202.4 W.m-1.K-1, each of which has a constant heat source equal to 6060.606 W.m-3. The air flow enters the room through ducts designed on top of one of the transformer room walls (with speeds equal to 1,531 ms-1 and 2.04 ms-1, with an angle equal to 45 degrees and at a temperature equal to 303.15 K), and exists through the outlets (with a pressure equal to atmospheric pressure).

For better distribution of hot air flow out of the room, louver windows connected to the exhaust ducts are used, each of which has a porosity coefficient equal to 0.6 and a viscosity resistance (1/ permeability) of 211100000 1.m-2 . Also, convection heat transfer around the walls of the transformer is assumed. The fluid bulk temperature is equal to 300 K and the heat transfer coefficient is equal to 24 W.m-2.K-1.

Transformer Room Geometry & Mesh

The present model is designed in three dimensions using Design Modeler software. The model consists of a two-part room with a thin membrane. This room has 10 air inlet ducts through the top of the room and 4 ducts for air outlet on the side walls. In this room, 3 transformers are designed as heat sources. A porous (louver window) medium is also used for each airflow outlet.

The meshing of the model has been done using ANSYS Meshing software, and the mesh type is unstructured. The element number is 592411. The following figure shows the mesh.

Transformer Room Ventilation CFD Simulation

We consider several assumptions to simulate the present model:

• We perform a pressure-based solver.
• The simulation is steady.
• The gravity effect on the fluid is equal to -9.81 m.s-2 along the Y-axis.

The following table represents a summary of the defining steps of the problem and its solution:

Models
Viscous		k-epsilon
	k-epsilon model	standard
	near wall treatment	standard wall functions
Energy		On
Boundary conditions
Inlet 1-2-6-7		Mass Flow Rate
	mass flow rate	1.531 kg.s-1
	temperature	303.15 K
Inlet 3-4-5-6-8-9-10		Mass Flow Rate
	mass flow rate	2.04 kg.s-1
	temperature	303.15 K
Outlet 1-2-3-4		Pressure Outlet
	gauge pressure	0 pascal
Inner Walls of Room, Transformers, Louvre		Wall
	thermal conditions	convection
	free stream temperature	300 K
	heat trasnsfer coefficient	24 W.m-2.K-1
Outer Walls of Room, Transformers, Louvre		Wall
	thermal conditions	coupled
Methods
Pressure-Velocity Coupling		Coupled
	Pressure	second order
	momentum	second order upwind
	turbulent kinetic energy	first order upwind
	turbulent dissipation rate	first order upwind
	energy	second order upwind
Initialization
Initialization methods		Standard
	gauge pressure	0 pascal
	velocity	0 m.s-1
	temperature	303.15 K

Results

At the end of the solution process, two-dimensional contours related to pressure, temperature and velocity were obtained in three different sections of the model, including y-z, x-y, and x-z.

There is a mesh file in this product. By the way, the Training File presents how to solve the problem and extract all desired results.