Computer Room Air Conditioning (Radiant Heat Transfer & DPM)

Description

Project Description

The present problem simulates the process of air conditioning in an office with several computers and simulators using ANSYS Fluent software. The air conditioning system in the current model is of floor heating and ceiling cooling; In this way, the effect of buoyancy causes free heat transfer inside the office space. Due to the lightness, the hot air moves from the floor to the ceiling, and the cold air does the opposite, thus creating a circulating flow that causes the air conditioning process.

In this model, due to the presence of radiant heat transfer between the surfaces inside the office, the radiation model is defined. Also, to study the behavior of air flow and the type of its circulation inside the interior of the office, particles are defined using the DPM model of inlet sections. Thus, by examining the behavior and type of displacement of these particles, the flow of air flow can be analyzed. In this modeling, air flow enters the office from circular sections as inlet from the office floor with a speed of 0.6125 m.s-1 and a temperature of 291.1 K and exits through rectangular sections on the office roof with a pressure equal to atmospheric pressure.

Inside the office, there are four computer cases and four simulators that, due to their function, generate a certain amount of heat and transfer it to the interior of the office. Four case devices have a heat flux boundary condition of 152.5 W.m-2 and four simulators have a heat flux boundary condition of 90.56 W.m-2.

Computer Room Geometry & Mesh

The present model is designed in three dimensions using Design Modeler software. The geometry of the model includes an office desk measuring 6.35 m and 5.4 m at floor level and 2.7 m high, in which four computer cases and four simulators are located as heat sources. There are also sections as air inlets and outlets on the floor and ceiling of the office.

The meshing of the model has been done using ANSYS Meshing software and the mesh type is unstructured. The element number is 3089035. The following figure shows the mesh.

Air Conditioning CFD Simulation

To simulate the present model, several assumptions are considered:

• 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	realizable
	near-wall treatment	standard wall function
Radiation Model		S2S
	solar load	off
Discrete Phase Model		On
	interaction with continuous phase	active
	particle type for injection	inert
	injection type	surface
	particles’ diameter	0.000001 m
	particles’ temperature	300 K
	particles’ velocity	0.6125 m.s-1
	particles’ flow rate	0.000004896 kg.s-1
Energy		On
Boundary conditions (Air Conditioning)
Inlet		Velocity Inlet
	velocity magnitude	0.6125 m.s-1
	temperature	291.1 K
	internal emissivity	1
	discrete phase BC type	escape
Outlet		Pressure Outlet
	gauge pessure	0 Pascal
	internal emissivity	1
	discrete phase BC type	escape
Side Walls		Wall
	wall motion	stationary wall
	heat flux	0 W.m-2
	internal emissivity	1
	discrete phase BC type	reflect
Heat Wall		Wall
	wall motion	stationary wall
	heat flux	193.95 W.m-2
	internal emissivity	1
	discrete phase BC type	reflect
Cases		Wall
	wall motion	stationary wall
	heat flux	152.5 W.m-2
	internal emissivity	1
	discrete phase BC type	reflect
Simulators		Wall
	wall motion	stationary wall
	heat flux	90.56 W.m-2
	internal emissivity	1
	discrete phase BC type	reflect
Methods (Air Conditioning)
Pressure-velocity coupling		SIMPLE
	pressure	second order
	density	second order upwind
	momentum	second order upwind
	turbulent kinetic energy	first order upwind
	turbulent dissipation rate	first order upwind
	energy	second order upwind
Initialization (Air Conditioning)
Initialization methods		Hybrid

Results

At the end of the solution process, two-dimensional and three-dimensional contours related to pressure, velocity, temperature and three-dimensional velocity vectors are obtained.

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.