Encyclopaedia Index

Flair User Guide

CHAM Technical Report TR 313

last revised 19/08/2010

Contents

  1. Introduction

    1.1 What is FLAIR ?
    1.2 What FLAIR can do

  2. Getting started
    2.1 Modes of FLAIR operation
    2.1.1 VR-Environment
    2.1.2 Satellite

    2.2 Accessing the FLAIR on-line help

    2.3 A simple example
    2.3.1 Problem description
    2.3.2 Setting up the model
    2.3.3 Running the Example
    2.3.4 Viewing the Results with VR-Viewer
    2.3.5 Printing from VR
    2.3.6 Summary

  3. The HVAC-specific object files and object types

    3.1 The HVAC specific object types
    3.1.1 Diffuser
    3.1.2 Fire
    3.1.3 Jetfan
    3.1.4 Spray-head type
    3.1.5 Person
    3.1.6 People

    3.2 The HVAC-specific objects and their default attributes
    3.2.1 Cabinets subdirectory
    3.2.2 JETFANS subdirectory
    3.2.3 Living subdirectory
    3.2.4 PERFPLAT subdirectory

    3.3 How to import the HVAC objects
    3.3.1 Using the Object Management dialog box
    3.3.2 Object attributes
    3.3.3 Exporting Object
    3.3.4 Object sizing, scaling and positioning
    3.3.5 Object Colouring and Rotation options
    3.3.6 Import custom geometry

  4. HVAC-Related Models
    4.1 Main Menu - Top Panel

    4.2 System curve

    4.3 Fan operating point

    4.4 Comfort Index
    4.4.1 Dry resultant temperature (TRES)
    4.4.2 Predicted mean vote (PMV)
    4.4.3 Predicted percentage dissatisfied (PPD)
    4.4.4 Draught rating (PPDR)
    4.4.5 Predicted productivity loss (PLOS)
    4.4.6 Mean age of air (AGE)

    4.5 Solve specific humidity

    4.6 Solve smoke mass fraction
    4.6.1 Optical smoke density
    4.6.2 Visibility - Sight length
    4.6.3 Light Intensity reduction
    4.6.4 Derived quantities
    4.6.5 Fire products data

  5. References
  6. Tutorials
  7. Q1 Settings
    7.1 Diffuser
    7.2 Fire
    7.3 Jetfan
    7.4 Sprayhead
    7.5 Person
    7.6 People

1. Introduction

1.1 What is FLAIR ?

FLAIR is a special-purpose program for Heating, Ventilation and Air Conditioning (HVAC) systems that are required to deliver thermal comfort, health and safety, air quality, and contamination control. FLAIR provides designers with a powerful and easy-to-use tool which can be used for the prediction of airflow patterns, temperature distributions, and smoke movement in buildings and other enclosed spaces. For example:

Figure 1.1 The temperature distribution in Hackney Hall

Figure 1.2 The temperature distribution in a computer room

Figure 1.3 Temperature contours of the hot gases from a fire on a plane through the central space of a multi-storey car park (all temperatures above 100 degree C are shown in red)

Figure 1.4 Wind test over Melbourne cricket ground

As seen from above examples, FLAIR can be used during the design process to detect and avoid uncomfortable air speeds or temperatures. In addition, it can predict the effects of any gaseous pollutant, helping to achieve safe design of buildings, underground systems etc. It can also be used by various regulatory bodies and safety consultants.

FLAIR provides a state-of-art Virtual Reality User Interface for rapid model creation and visualisation of the results, including various thermal-comfort parameters. Little CFD knowledge is therefore required to operate FLAIR or to understand this guide.

1.2 What FLAIR can do

All the functions that are required to create a FLAIR model, to solve the problem, to examine the results and On-line help can be accessed through a single integrated FLAIR-VR interface.


2. Getting started

This chapter gives instructions for starting the FLAIR application. Following a simple example, you will use FLAIR to set up a problem, solve the problem and view the results. This is only a basic introduction to the features of FLAIR. Working through more tutorials described in Chapter 6 will provide a more complete demonstration of the program's features.

2.1 The Modes of FLAIR operation

The FLAIR pre-processor has several modes of operation. These are:

For details about how to start FLAIR in the Satellite mode, the user is referred to PHOENICS document, Tr326. This document uses the FLAIR VR-Environment for this simple example.

2.2 Accessing the FLAIR on-line help

  1. HELP Button on FLAIR VR-Environment Top menu.

    The Help button on the Help menu leads directly to this document and other documentation section of POLIS (PHOENICS On-line Information system) as shown below.

  2. Bubble-help in VR interface hand-set.

    In FLAIR VR, information on the various hand-set control buttons can be displayed when the cursor is held stationary over any relevant control button. For example, when the cursor is held stationary over 'Menu' button, 'Domain attributes menu' will be displayed as shown below.

  3. Help in the 2D-menu of the FLAIR VR and Object dialog boxes.

    The following additional on-line help is available in the main menu of the FLAIR VR-Environment.

    Click on the 'Help' button in the top menu for help on the main menu.

    Click on the '?' in the top-right corner of any dialog box, then click on any input window or button to get information on the parameter which is set in it.

    For example, if you want to obtain the information about Energy Equation, 'Temperature', click on the '?', in the top-right corner of any dialog box, then click on 'Temperature' button, the following information will be displayed:

2.3 A simple example

2.3.1 Problem description

Figure 2.1 shows the geometry of the example. The problem solved involves a room containing an air opening, a vent, a standing person, floor and walls held at a constant temperature. The room is 5m long, 3m wide, and 2.7m high. The opening measures 0.8 m x 1.0 m and introduces a cold air jet into the room to ventilate it. The vent is 0.8 m x 0.5 m. The interaction of inertial forces, buoyancy forces, and turbulent mixing is important in affecting the penetration and trajectory of the supply air.

Figure 2.1 The simple example

We will take the following steps to set up the model:

  1. to start the FLAIR application with the default room
  2. to re-size the room
  3. to add objects to the room
  4. to activate the physical models
  5. to specify the grid number in each direction (the grid will be generated automatically) and specify solver parameters
  6. to calculate a solution
  7. to examine the results

The remaining sections provide step-by-step instructions on how to set up the model.

2.3.2 Setting up the model

  1. Starting FLAIR

            

Figure 2.2a The 'File' menu Figure 2.2b 'Start New case' dialog

The FLAIR VR-Environment screen shown in figure 2.3 below should appear, which consists of two components: the Main window and the control panels (on the right).

Figure 2.3 The FLAIR-VR environment

FLAIR will create a default room with the dimensions 10m x10m x3 m, and display the room in the graphics window.

You can rotate, translate, or zoom in and out from the room by clicking the 'Mouse' button on the movement control panel and then using left or right mouse buttons.

2.3.2 Resizing the room

Figure 2.4 Resize the default room to 3mx5mx2.7m on the control panel

Figure 2.5 The resized room

2,3.4 Adding objects to the room

a. add the first object, which will act as a person in the room.

Figure 2.6 The Object management dialog Box.

Figure 2.7 The Object specification dialog box

Figure 2.8 The PERSON's attributes panel

Set:

Body width: 0.6 m

Body depth: 0.3 m

Body height: 1.76 m

X: 1.5 m

Y: 2.0 m

Z: 0.0 m

Click on 'OK' to close the dialog box.

b. Next add a vent.

X:0.8 m

Y:0.0 m

Z:0.5 m

X: 3.2 m

Y: 0.0 m

Z: 0.0 m

c. Next add an Opening:

X:0.8 m

Y:0.0 m

Z:1.0 m

X: 1.19 m

Y: 5.0 m

Z: 1.5 m

d. Next to add the adiabatic Floor:

X:3.0 m

Y:5.0 m

Z:0.0 m

X: 0.0 m

Y: 0.0 m

Z: 0.0 m

  1. Next add the wall at x = 0

X:0.0 m

Y:5.0 m

Z:2.7 m

X: 0.0 m

Y: 0.0 m

Z: 0.0 m

Figure 2.10 The attributes of the wall at x=0

Figure 2.11 The screen picture after all the object were created

To activate the physical models

a. The Main Menu panel

Figure 2.12 The Main Menu top page.

While this panel is on the screen, you may set the title for this simulation, click on the 'Title' dialogue box. Then type in a suitable title, for example 'My first flow simulation'.

FLAIR always solves pressure and velocities. The temperature is also solved as the default setting.

Figure 2.13 The 'Models' page of the Main Menu.

b. To activate LVEL turbulence model

Figure 2.14 Select LVEL on the "Turbulence Models" page of the Main Menu.

To set the grid numbers and solver parameters

Figure 2.16 Geometry menu page

This mesh is adequate for the example, but would need to be refined for a more accurate solution. The function of the Grid Mesh Settings dialog is explained in TR326.

Set the number of sweeps in this window to 500 as shown in figure 2.17.

Figure 2.17 Set the " Total number of iterations' to 300

Figure 2.18 Monitoring position

It can also be set by clicking on 'Output' on the main menu. For this case, the monitor-cell location, (11,19,7) will be displayed.

2.3.3 Running the Example

FLAIR uses the PHOENICS solver called 'Earth'.

To run Earth, click on 'Run', and then 'Solver', followed by clicking 'OK' to confirm running Earth. These actions should result in the PHOENICS Earth screen appearing.

As the Earth solver starts and the flow calculations commence, two graphs should appear on the screen. The left-hand graph shows the variation of pressure, velocity and temperature at the monitoring point that was set during the model definition. The right-hand graph shows the variation of errors as the solution progresses.

As a converged solution is approached, the values of the variables in the left-hand graph should become constant. With each successive sweep number, the values of the errors shown in the right-hand window should decrease steadily.

Figure 2.19 shows the EARTH monitoring screen at the end of the calculation.

Figure 2.19 The EARTH run screen at the end of calculation

Runs can be stopped at any point by following the procedure outlined below.

Please note: if the solver is stopped before the values of the variables in the left-hand graph of the convergence monitor approach a constant value, the solution may not be fully converged, and the resulting flow-field parameters may not be reliable.

2.3.4 Viewing the Results with VR-Viewer

The results of the flow-simulation can be viewed with the FLAIR VR post-processor called VR-Viewer.

In the VR-Viewer, the results of a flow simulation are displayed graphically. The post-processing capabilities of the VR-Viewer that will be used in this example are:

Accessing the VR-Viewer

To access the VR Viewer, simply click on the 'Run' button, then on 'Post processor', then 'GUI Post processor (VR Viewer)' in the FLAIR-VR environment.

When the 'File names' dialog appears, click 'OK' to accept the current result files. The screen shown in figure 2.19 should appear.

Figure 2.19 The VR-Viewer screen picture as it appears for this case.

Viewing the Results with VR-Viewer

The detailed description of the VR-Viewer screen and hand set control buttons is provided in PHOENICS documentation TR326. This section simply gives instructions on how to view the results.

To view the results of the simple simulation just completed:

Figure 2.20 The Streamline management dialog

Figure 2.21 Stream Options dialog box

Typical displays of a vector, contour and a streamlines plot are shown below in figures 2.22 (a - c) respectively.

Figure 2.22a Vector plot.

Figure 2.22b Contour plot.

 

Figure 2.22c Streamlines.

2.3.5 Printing from VR.

Screen images such as figures 2.22(a - c) can be sent directly to a printer by clicking on 'File', then on 'Print' from the main environment screen. A dialog similar to that shown in figure 2.23a opens.

Figure 2.23a Print Dialog Box

Alternatively, the screen image can be saved to a file by clicking on 'File', then on 'Save window as' from the main environment screen.

When 'Save window as' has been pressed, the dialog box shown in figure 2.23b opens.

Figure 2.23b 'Save Window as' Dialog Box

The 'Save as file' dialog offers a choice between GIF, PCX and BMP file formats, and allows the image to be saved with a higher (or lower) resolution than the screen image.

The graphics files are dumped in the selected folder (directory), with the given name. In all cases, the background colour of the saved image is that selected from 'Options', 'Background colour' from the VR-Editor main environment screen.

2.3.6 Summary

The above example has been designed to show how to use FLAIR to solve a very simple problem. More examples are provided in chapter 6, Tutorials, where how to use the different modeling objects, physical models and post-processing capabilities that are available in FLAIR are described in more detail.


3. The HVAC-specific object files and object types

3.1 The HVAC-specific object types

FLAIR provides six HVAC-specific object types, Diffuser, Fire, Jetfan, Spray-head, Person and People as described below.

3.1.1 Diffuser

The Diffuser is a single object representing a complex source of mass, momentum and energy. It is used to represent various types of diffusers found in rooms and buildings. The detailed implementation is based on the 'Momentum method' described in ASHRAE Report RP-100915.

The diffuser object can be accessed through the Object management dialog box. To load a diffuser object, click on the 'Obj' button on the main control panel to bring up the Object management dialog box. Then click on 'Object' , 'New' and 'New object' pull-down menu to bring up the Object specification dialog box. Select Diffuser from object 'Type' as shown in figure 3.1.

Figure 3.1 Selecting Diffuser from the object 'Type'

The default diffuser is the 4-way diffuser. Figure 3.2 shows the default diffuser attributes.

Figure 3.2 The default diffuser and its attributes

The following specifications can be defined through the attributes panel:

Diffuser type - there are 5 different types as shown in figure 3.3. Each type has its own shape.

Figure 3.3 The select diffuser type panel

The diffuser types have the following characteristics:

Figure 3.4 Round diffuser

Figure 3.5 Vortex diffuser, 45deg swirl angle.

Figure 3.6 4-way rectangular diffuser

Figure 3.7 4-way directional diffuser, all faces active

Figure 3.8 Grille diffuser, 45 deg symmetrical deflection

Figure 3.9 Displacement diffuser, 4 sides and top face active

Diffuser Attributes

All diffuser types can be rotated freely about any axis or combination of axes. Note however that if Grille, Round, Vortex or 4-way rectangular diffusers are rotated out of the plane of the grid, they must lie on the face of a BLOCKAGE object otherwise they will produce no flow.

Diffuser position - for all diffusers other than displacement, these set the coordinates of the centre of the mounting face of the diffuser. For displacement diffusers, it sets the low x,y,z corner.

Diffuser diameter - for round and vortex diffusers, this sets the diameter of the diffuser.

Diffuser size - for rectangular diffusers, sets the length of the faces.

Plane - This allows the user to place the diffuser in the X, Y or Z planes.

Side - When the diffuser is mounted internally in the solution domain, the diffuser itself can be on the decreasing-coordinate (low) or the increasing-coordinate (high ) side of the mounting face. The position boxes set the location of the mounting face - this controls whether the diffuser is above or below, to the left or right.

X/Y/Z Faces - For 4-way directional and displacement diffusers, these control which faces of the diffuser are active. The supply volume is divided uniformly amongst the active faces.

The face directions and deflection angles referred to below are always in the coordinate system of the diffuser itself, not taking into account any rotations. For example, consider a 4-way directional diffuser in the X-Y plane which has been rotated +90deg about Z. The high X face of the diffuser will now point along Y.

Supply pressure - This sets the pressure of the supply air, relative to the Reference Pressure set on the Properties panel of the Main menu (usually 1.01325E5 Pa). It is used together with the supply temperature to calculate the density of the supplied air. By default it is set to the ambient pressure, which is also set on the Properties panel. Any other value can be entered by switching to 'User'.

Supply temperature - This sets the temperature of the supply air in degree C. By default, it is set to the ambient temperature, which is set on the Properties panel of the Main menu. Any other value can be entered by switching to 'User'.

Supply volume - This sets the volumetric flow rate for the supply air in L/s or m3/s.

Set throw or effective area - The diffuser can be defined either in terms of the Effective area or Throw and terminal velocity. These factors are usually obtained from manufacturer's data sheets.

The Effective area can be deduced by dividing the supply volume flow rate by the discharge velocity. It is always less than the nominal plan area.

If the Throw and terminal Velocity are set, the discharge velocity and hence Effective area are deduced using a jet formula and the jet decay constant.

The depth of the diffuser (except grille and displacement) is deduced by dividing the Effective area by the active perimeter.

Swirl angle (for Vortex type only) - This sets the amount of swirl induced by the diffuser. A value of zero gives no swirl (equivalent to a round diffuser); the flow is purely radial. A value of 90 means the flow is purely tangential. Positive angles produce anti-clockwise swirl when looking down on the diffuser. This is usually the angle the diffuser blades are set to.

Angles from Z axis (for Grille/Nozzle type only) -

image104.gif (29618 bytes)

Figure 3.10 The Grille diffuser and its attributes

This specifies the deflection from the normal to the plane of the diffuser in each of the other two directions. If the plane is The default value of 0.0 means no deflection- the flow comes out normal to the diffuser surface. Positive values mean deflection in the + axis direction; negative values mean deflection in the - axis direction. The deflection is limited to +/- 89 degrees.

When the Symmetric Yes/No switch is set to Yes, the flow is divided symmetrically in the positive and negative axis directions. It is as if the grille were made up of two grilles with opposite deflection angles. When set to No, both halves use the same deflection angle. As the grille is divided horizontally and vertically, there are actually four sources for each grille.

Effective area ratio (for displacement type only) - For a displacement diffuser, this is the ratio between the true flow area and the modeled area. It is the same for all active faces.

3.1.2 Fire

The fire object is used to create an area or volumetric heat source, representing a fire. There are several options for setting the heat, mass and smoke sources at the fire. It is assumed that the mass released by the fire is the products of combustion, and that the SMOK variable represents the local mass fraction of combustion product.

Some combinations require the Heat of Combustion Hfu and the stoichiometric ratio, Rox to be set. If the product mass-fraction SMOK is solved, these values are set in Main menu - Solve smoke mass fraction - settings. If SMOK is not solved, these settings can be made on the Fire object dialog.

The fire can be loaded through the Object management in the same way as described in section 3.1.1 above for the diffuser.

The default fire object and its attributes are shown in figure 3.11 below.

image100.gif (29245 bytes)

Figure 3.11 The fire and its default attributes

The dialog will change as different options are selected, showing input boxes for the various parameters.

Heat Source

The heat source set here is the total heat source Qt =Qconvective + Qradiative. If the radiation model is not active, the heat source reported in the solution (as 'Source of TEM1') is reduced by the Radiative fraction Rf to be just the convective part. The Radiative factor is set on the 'Smoke settings' panel of the Main Menu, and is defaulted to 0.3333. The total heat release rate is still used to derive the smoke mass source

The options for the Heat source are:

image101.gif (11190 bytes)

Figure 3.12 Fire heat sources

Time,Qt
0,0
60,350000
120,700000
180,1050000
240,1400000
300,1400000
360,1400000
420,1400000
480,1400000
540,1400000
600,2055000

The Earth solver will perform a linear interpolation in the table to find the heat source for any particular time. The time in the table is the time since ignition. This option allows for any number of points in the table, and should be used in preference to 'Piece-wise Linear in time' if there are more than 10 points.

In a transient case, a file called 'heat_sources.csv' will be created. It will contain the convective heat source for each fire object for each time step. An example is given here:

Time ,     FIXMAS ,   POOL ,      PWLM ,     FIXT ,      FIXQ ,     LINTEM ,
3.000E+01, 1.100E+05, 7.705E+05, 1.719E+03, 0.000E+00, 1.320E+06, 1.005E+05,
9.000E+01, 1.100E+05, 1.346E+06, 5.156E+03, 2.747E+05, 1.320E+06, 1.005E+05,
1.500E+02, 1.100E+05, 2.011E+06, 8.594E+03, 2.747E+05, 1.320E+06, 1.005E+05,
2.100E+02, 1.100E+05, 2.753E+06, 1.203E+04, 2.747E+05, 1.320E+06, 1.005E+05,
2.700E+02, 1.100E+05, 3.561E+06, 1.547E+04, 5.493E+05, 1.320E+06, 1.005E+05,

The first column is the solver time, at the mid-point of each time step. The subsequent columns are the heat release rates in Watts for the FIRE objects named in the first row.

Mass Source

The options for the Mass source are:

image102.gif (10530 bytes)

Figure 3.13 Fire mass sources

The mass released is taken to be the products of combustion:

1kg Fuel + Rox kg Oxygen = (1+Rox) kg Product

In a transient case, a file called 'smoke_sources.csv' will be created. It will contain the product mass (smoke) source for each fire object for each time step. An example is given here:

Time ,     FIXMAS ,   POOL ,      PWLM ,     FIXT ,      FIXQ ,     LINTEM ,
3.000E+01, 2.000E-02, 1.401E-01, 3.125E-04, 8.182E-05, 2.400E-01, 1.828E-02
9.000E+01, 2.000E-02, 2.446E-01, 9.375E-04, 8.182E-05, 2.400E-01, 1.828E-02
1.500E+02, 2.000E-02, 3.656E-01, 1.562E-03, 8.182E-05, 2.400E-01, 1.828E-02
2.100E+02, 2.000E-02, 5.005E-01, 2.187E-03, 8.182E-05, 2.400E-01, 1.828E-02
2.700E+02, 2.000E-02, 6.474E-01, 2.812E-03, 8.182E-05, 2.400E-01, 1.828E-02

The first column is the solver time, at the mid-point of each time step. The subsequent columns are the mass release rates in kg/s for the FIRE objects named in the first row.

Scalar Source

The options for the Scalar source are:

image103.gif (9777 bytes)

Figure 3.14 Fire smoke sources

The SMOK scalar is taken to be product of combustion - the inlet value is therefore always 1.0. The parameters determining how the smoke concentration affect visibility are all set in  Main menu - Solve smoke mass fraction - settings.

Note that some of the source types are only available for transient simulations. Not all source types are mutually compatible - for example if the mass source is 'heat related', the heat source cannot be 'mass related'. Such incompatible combinations will be flagged up as errors when trying to set them.

InForm - InForm sources are set through the InForm Commands button. This leads to a dialog from which a selection of InForm commands can be attached to this object. It is described here.

3.1.3 Jetfan

The jetfan object is used to create a volume of fixed velocity, representing the effects of a jetfan. The velocity components in the domain X-, Y- and Z-axes are calculated internally to give the set total velocity and direction.

The jetfan can be loaded through the Object management in the same way as described in section 3.1.1 above for the diffuser.

The default jetfan object and its attributes are shown in figure 3.15 below.

image88.gif (22234 bytes)

Figure 3.15 The jetfan and its default attributes

Fan type - The fan can be rectangular or circular in cross-section. Unless the grid is very fine, the difference will be mainly visual.

Xpos, Ypos, Zpos - Sets the location of the centre of the jetfan object. Any rotations set will be about this point.

Length - Sets the length of the jetfan in the X co-ordinate direction of the jetfan.

Width - Sets the width of a rectangular jetfan in the Y co-ordinate direction of the jetfan.

Depth - Sets the depth of a rectangular jetfan in the Z co-ordinate direction of the jetfan.

Diameter - Sets the diameter of a circular jetfan.

Velocity - Sets the delivery velocity of the jetfan in the X co-ordinate direction of the jetfan. The jetfan always blows along its own X-axis. The jetfan can be rotated about its centre to point in any desired direction.

Set turbulence intensity - when Yes, sets the turbulence intensity for the jetfan. Typical values may be in the range 20 - 25%. The turbulence quantities are set from:

KEjet = (Intensity/100 * Velocity)2 ; EPjet = 0.1643*KEjet3/2/(0.1*diameter)

For a rectangular jetfan, the diameter is taken as 0.5*(Height+Width).

When No, the jetfan has no direct impact on the turbulence field other than by creating additional velocity gradients.

The default setting is No. When switched to Yes, a value of 22% is set.

Heat load - Sets the heat gain (or loss) through the jetfan. The default setting of 0.0 ensures there is no heat gain or loss. Positive values represent a heat gain, as through a heater, negative values represent a loss, as through a cooler.

Angle to X axis - Sets the inclination of the jetfan X co-ordinate to the domain X-axis. The resulting flow direction is as shown in the table below:

Angle Jet direction
0 +X
90 +Y
180 -X
270 -Y

Angle to Z axis - Sets the inclination of the jetfan X co-ordinate to the domain Z-axis. The default angle of 90 directs the jet parallel to the floor. Angles > 90 incline the jet towards the floor, angles < 90 incline the jet towards the ceiling.

3.1.4 Spray-head

The spray-head is the sprinkler designed for fire extinction. It works with the GENTRA module (see Encyclopaedia in POLIS). The spray-head can be loaded through the Object management in the same way as described in section 3.1.1 above for the diffuser.

The default spray-head object and its attributes are shown in figure 3.16 below.

Figure 3.16 The default spray-head object

The following specifications can be defined in the attributes dialog box:

Spray axis direction - This sets the axis of the spray to be along the positive X, Y or Z axis. The spray-head disk is normal to the selected axis.

Spray position - This sets the location of the centre of the spray-head disk. The disk is always normal to the spray axis.

Spray radius - This sets the radius of the spray-head disk. The droplet injection ports are uniformly distributed along the circumference of the disk.

Number of ports - This sets the number of the injection ports around the circumference of the spray disk.

Total volume flow rate - This sets the total volumetric flow rate of the water to be injected from the spray. The total amount is divided equally among the injection ports. The units are always litres/second.

Total injection velocity - This sets the velocity with which the droplets are deemed to be injected.

Spray angle (from spray axis) - This sets the angle between the spray and the spray axis. When set to 0.0, the droplets will be injected in the direction of the positive spray axis. Usually this will mean vertically upwards. When set to 90, the droplets will be injected normal to the axis. Usually this will mean horizontally. When sets to 180, the droplets will be injected in the direction of the negative spray axis. Usually this will mean vertically downwards.

Injection temperature - This sets the temperature of the injected droplets. The units are always degree C.

Volume median diameter - 50% of the water, by volume, is contained in droplets of this or greater diameter. Other 50% is contained in smaller droplets.

Number of size ranges - This sets number of droplet size to be considered. When sets to 1, the droplets will take volume median diameter. When sets to greater than 1, the sizes used will lie between the set minimum and maximum values, and will be distributed according to the Rosin-Ramler droplet distribution function.

Calculate link temperature (appears for transient run only) - This determines whether the link temperature for the spray will be calculated or not. If 'Calculate link temperature' is set to 'Yes', then two more entries, Activation temperature and Response time Index, will appear. The Track start- and end-times will be reset to 'Auto-on', and a new data entry box will appear for setting the duration of the spray after initiation.

Activation temperature is the temperature at which the track is to start.

Response Time Index (RTI) is a measure of the detector sensitivity.

The link temperature is calculated from17:

dTl/dt = e(|Vel|) (Tg-Tl/) / RTI
where Tl is the link temperature, Vel is the gas velocity and Tg is the gas temperature.

The calculated link temperatures are written to the file 'tlink1'csv' at the end of each time step. If there are more than 20 sprays, each group of 20 will be written to a separate 'tlinkn.csv' file where n is 1,2,3 etc.

A tutorial is provided in section 6.9 which shows how to use the Spray-head object for the simulation of fire extinction.

If GENTRA is not active at the time the first spray-head object is created, it will be automatically turned on, with all settings made for the spray model. Only the spray start- and end-times need be set for a transient case, should the spray not be active all the time.

If GENTRA is already turned on, it will be assumed that all settings as correct, and no default settings will be made.

The settings made for GENTRA are:

3.1.5 Person

The Person object represents the heat load effect of a single human being. It does not apply a resistance to motion.

 

Figure 3.17 The default Person object

The 'Posture' button allows a choice of 'Standing' (as in the image above), 'Sitting' or 'User'. If 'User' is selected, the Size and Position dialogs on the Object Specification dialog can be used to  size and rotate the image. The 'Facing' button toggles through +X,-X,+Y and -Y to determine which direction the person faces. 

The heat source can be Total heat in W, of fixed temperature in Centigrade.

3.1.6 People

The People object is used to represent the heat load of a large number of people, for example the audience in a theatre. It does not apply a resistance to motion.

Figure 3.18 The default People object

3.2 The HVAC-specific objects and their default attributes

The predefined HVAC-specific object files contain both geometry information and the default attributes of the object or assembly. They are stored in the directory /phoenics/d_satell/d_object/public/flair and its subdirectories as described below.

3.2.1 Cabinets subdirectory contains the following object files:

3.2.2 Jetfans subdirectory contains the following model files:

Figure 3.23 The Fan+x20 assembly

The internal fan is located in the middle of the duct and its attributes are shown in figure 3.24.

Figure 3.24 The attributes of the fan

3.2.3 Living subdirectory contains the following model files

Figure 3.25 The sitting-man and the standing-man

Figure 3.26 The attributes of the sitting-man

3.2.4 Perforated Plates subdirectory contains

Figure 3.27 The default attributes of the perforated plate

  3.3 How to import the HVAC objects


4. HVAC-Related Models

As a special version of PHOENICS, FLAIR has the following HVAC-related models: system curve, fan operating point, humidity calculation, comfort index and smoke movement.

This chapter is to provide detailed descriptions about how to activate these models.

All these models can be set up through the Main Menu in FLAIR VR-Editor. The main menu is reached by clicking the Main Menu button, on the hand-set. This brings up the Main Menu top panel.

4.6.4 Derived quantities

In addition to the solved-for combustion-products mass fraction (SMOK), the two sight length variables SLEN and SLN2 and the optical density OPTD, the following derived quantities can be calculated and stored:

4.6.5 Fire products data

For various fire materials, Table 4.6.3.1 provides suggested values of heats of combustion and yields of smoke particulates and carbon monoxide ( see CIBSE Guide E [20034] )

Material Hfu (MJ/kg) Yco (kg/kg) Ys (kg/kg)
Timber 13.0 0.020 <0.01 - 0.025
PVC- Polyvinyl chloride 5.7 0.063 0.12 - 0.17
PU- Polyurethane (flexible) 19.0 0.042 <0.01 - 0.23
PU- Polyurethane (rigid) 17.9 0.18 0.09 - 0.11
PS- Polystyrene 27.0 0.060 0.15 - 0.17
PP- Polypropylene 38.6 0.050 0.016 - 0.1

Table 4.6.3.1 Fire data for flaming combustion

Heat release rates, heats of combustion and yields for other materials can be found in the literature. For example, Babrauskas et al [198513, 199211,12] examined the fire behaviour of upholstered furniture, and found that the data reported varied considerably with the component materials for the frame, cushioning material and upholstery fabric. Typical values for a traditional upholstered easy chair are Hfu=18MJ/kg, Yco=0.05kg/kg and Ys=0.025kg/kg. NFPA 92B [20056] lists heats of combustion and heat release rates for a large number of combustible materials.

The stoichiometric ratio Rox can be estimated from the heat release rate Q by assuming that the heat released per unit mass of oxygen is constant ( Huggett [198014] ). In the literature, this ratio Hfu/Rox is taken as 13.1 MJ/kg and varies by only 5% for almost any common combustibles ( Babrauskas et al [198513, 199211,12] )


5. References

1. CIBSE Guide, Volume A, Design Data

2. ISO 7730 Second Edition 1994-12-15
Moderate thermal environments - Determination of the PMV and PPD indices and specification of the conditions for thermal comfort.

3. Roelofsen, Paul. Journal of Facilities Management Volume 1, Number 3 November 2002 ISSN 1472-5967
The impact of office environments on employee performance: The design of the workplace as a strategy for productivity enhancement

4. Fire Engineering CIBSE Guide E, ISBN 1 903287 31 6, CIBSE, London, (2003).

5. T.Jin, 'Visibility through fire and smoke', J.Fire & Flammability, Vol.9, pp135-155, (1978).

6. NFPA 92B, 'Standard for smoke management systems in malls, atria and large spaces', NFPA, Quincy, Massachusetts 02269-9101, USA, (2005).

7. G.W.Mulholland & C.Croarkin, 'Specific extinction coefficient of flame generated smoke', Fire & Materials, Vol.24, No.5, p227, (2000).

8. G.W.Mulholland, 'Smoke production and properties', Chapter 2, Section 13, p2-258, SFPE Handbook of Fire Protection Engineering, 3rd Edition, NFPA, Quincy, Massachusetts 02269-9101, (2002).

9. D.Drysdale, "An Introduction to Fire Dynamics", John Wiley, (2000);

10. B.P.Hushed, "Optical source units and smoke potential of different products" DIFT report 2004:1, DIFT, Denmark, (2004).

11. Babrauskas, V. "Generation of CO in Bench-Scale Fire Tests and the Prediction for Real-Scale Fires", Fire & Materials Int. Conf., Arlington, VA, USA, p155, (1992).

12. Babrauskas, V., J.R.Lawson, W.D.Walton & W.H.Twilley, "Upholstered furniture heat release rates measured with a furniture calorimeter", NBSIR 82-2604, USA (1992).

13. Babrauskas, V. & Krasny, J., "Fire Behaviour of Upholstered Furniture", NBS Monograph 173, NBS, USA(1985).

14. C.Huggett, 'Estimation of rate of heat release by means of oxygen consumption measurements', Fire & Materials, 4, 61-5, (1980).

15. Srebric, J., Chen Q., "Simplified Diffuser Boudary Conditions for Numerical Room Airflow Analysis", ASHRAE RP-1009, March 20, 2001

16. M.Tuomisaari, "Visibility of exit signs and low-location lighting in smoky conditions", VTT Publications 300, TRC of Finland, Espoo, (1997).

17. G.Heskestad & R.G. Bill, "Quantification of Thermal Responsiveness of Automatic Sprinklers Including Conduction Effects", Fire Safety Journal, 14:113-125, 1988.


6. Tutorials

In addition to the simple example described in chapter 2, this chapter provides further 9 examples, each of which gives step-by-step instructions, combined with pictures, show how to use various features in FLAIR to set up models, to run the solver and to view the result. These cases are:

Tutorial 1 Investigating library case I203 illustrates how to load a case from the FLAIR library, to investigate the model settings, to run the case and to view the results.

Tutorial 2 A room with two radiators shows how to activate the IMMERSOL radiation model. The 'Duplicate object' function is used for the creation of the second window and radiator. The material of the radiators is selected from the property data base. A fixed heat flux is used as the heat source for the radiators.

Tutorial 3 Comfort indices in a room is similar to tutorial 2, but adds a chair and a sitting person into the room. This tutorial demonstrates how to activate the comfort index option.

Tutorial 4 Fire in a room shows how to use the Fire object for simulating a fire in a room. Smoke movement is also simulated.

Tutorial 5 A room with sunlight describes how to use Shapemaker to create a sunlight object in the model building.

Tutorial 6 A cabinet with a fan illustrates how to use the 'fan working point' option and how to create a fan-data file for the simulation.

Tutorial 7 Flow in a computer room shows how to use 'Group' and 'Arraying objects' features to add the desks and computers. The case also shows how to load a round diffuser from the predefined HVAC object library.

Tutorial 8 Flow over Big Ben demonstrates how to import a CAD file in STL format into the FLAIR VR-Editor to create the geometry. This tutorial also shows how to use a Wind_profile object to describe the wind profile at the upstream boundary. The 'Paint' object capability in the VR-Viewer is used to draw the pressure contours on the object surface.

Tutorial 9 Fire-spray in a compartment shows how to use the spray-head object and GENTRA module for the simulation of a fire-spray in a compartment. This kind of application of the sprinkler is commonly adopted in a car park for fire extinction.

Tutorial 10 Fire modeling gives an example of the FIRE object for a typical t2 fire in a simple configuration. It also shows how the operation of jetfans can be controlled by a temperature sensor using InForm.


7. Q1 Settings
7.1 Diffuser
7.2 Fire
7.3 Jetfan
7.4 Sprayhead
7.5 Person
7.6 People


Contents