The Use and Application of CFD in the Air Conditioning and ... - Cham

The Use and Application ofCFD in the Air ConditioningSeminarand Fire Protection IndustryAIRAH NSW February 2008

The Use and Application of CFD in the AirConditioning and Fire Protection IndustrySeminarAn Introduction to CFDModelling usingPHOENICSBy Dr John LudwigConcentrated Heat and Momentum UK

What does CHAM do?Seminar“Simulation of processes involving fluid flow,heat transfer, chemical reaction &combustion within engineering equipmentand the environment”A-Z industrial & environmentalapplicationsPractical - Cost-effective - Validated- Easy to Use

A wide range of applicationsSeminarSmoke & fire spreadHeating & VentilationAerodynamicsImpeller pump efficiency

A wide range of applicationsSeminarHeat transferMulti-phaseParticle tracking

Main Features of PHOENICSSeminar• 1-,2- and 3-D geometries• Cartesian, Polar and Body-Fitted Coordinates• Local multi-level fine-grid embedding• Cut-cell technique for complex geometry• Conjugate Heat Transfer• Single or Multi-Phase Flow• Particle Tracking• Chemical reaction• Radiation• Non-Newtonian Flow• Choice of equation solvers and differencing schemes• Run-time implementation of user code – no recompiling• Automatic convergence control

Main Features of PHOENICSSeminar• PHOENICS consists of several modules:– VR-Editor for setting up problems,– EARTH for solving the problem,– VR-Viewer for visualising results; and– POLIS for providing information.• Together they allow users to solve a wide range of 1D, 2D and3D fluid flows simultaneously with heat transfer and chemicalreaction.

PHOENICS Key ComponentsSeminar• Model setup – VR Editor• Clicking on anobject brings adialogue box ontothe screen.• This enables theinformation aboutthe object to beedited.

PHOENICS Key ComponentsSeminar• Model setup – VR Editor• The object geometrycan be taken from alibrary of shapes, orloaded from a CADfile.• CAD geometries areread using the STLformat

Analysis of Results - VR ViewerSeminarThe VR Viewer allows users to see their results in a number ofdifferent ways:

Analysis of Results - VR ViewerSeminarStreamlines, static or animatedIso-surfacesContour planesVectors

What is FLAIR?Seminar• FLAIR is a Special-Purpose version of the generalCFD code PHOENICS.• It is aimed at the HVAC community.• It has been created by removing many unneededgeneric features, and adding several specificfeatures.

FLAIR FeaturesSeminar• FLAIR uses the PHOENICS VR-Editor to set theproblem up, with the following additional items:– ISO 7730 Comfort index calculations: PMV, PPD.– ISO 7730 Draught rating.– CIBSE dry resultant temperature.– Humidity calculations, with output of humidity ratio andrelative humidity.– Smoke movement calculation, with output of PPM, smokedensity and visibility.– Mean age of air calculation.– Fan operating point calculation for single and multiple fans.– System-curve calculations.

FLAIR FeaturesSeminar• In addition, the following object types have been added:– DiffuserRound

FLAIR FeaturesSeminar• In addition, the following object types have been added:– DiffuserVortex

FLAIR FeaturesSeminar• In addition, the following object types have been added:– DiffuserRectangular

FLAIR FeaturesSeminar• In addition, the following object types have been added:– DiffuserDirectional

FLAIR FeaturesSeminar• In addition, the following object types have been added:– DiffuserGrille

FLAIR FeaturesSeminar• In addition, the following object types have been added:– DiffuserDisplacement

FLAIR FeaturesSeminar• In addition, the following object types have been added:– Diffuser– Fire

FLAIR FeaturesSeminar• In addition, the following object types have been added:– Diffuser– Fire– Person (standingor sitting facing anyDirection)

FLAIR FeaturesSeminar• In addition, the following object types have been added:– Diffuser– Fire– Person– CrowdTo represent a large number of people as distributed source of heat

FLAIR FeaturesSeminar• In addition, the following object types have been added:– Diffuser– Fire– Person– Crowd– SunlightCreated inShapemaker

FLAIR FeaturesSeminar• In addition, the following object types have been added:– Diffuser– Fire– Person– Crowd– Sunlight– Spray head

FLAIR FeaturesSeminar• Spray-head represents sprinklers user for fire-suppression.• It uses GENTRA to model the droplet paths.• Evaporation is considered, and is linked to the FLAIRhumidity model.• The GENTRA inlet table iswritten automatically.

FLAIR FeaturesSeminar• In addition, the following object types have been added:– Diffuser– Fire– Person– Crowd– Sunlight– Spray head– Jet fan

Example Case StudiesSeminarThe following Application Examples will beshown:• Car Park Safety• Office Building Ventilation• External flow over buildings

SeminarPHOENICSCarpark Example

Car Park• This work was carried out as a Consultancy model-build insupport of ExcelAir BV in Holland.Seminar• It concerns the spread of smoke through a complex car parkas a result of a car fire on one of the lower floors.• The car park is spiral in form, with an open centre.• The car fire is 8.3 MW. After 180s, sprinklers on the floorwhere the fire is are activated.

Car Park - Geometry• Roof in placeSeminar

Car Park - Geometry• Roof removedSeminar

Car Park - Geometry• Roof, lift shafts and first floor removedSeminar

Car Park - Geometry• More floors removedSeminar

Car Park - Geometry• Fire and sprinklers on lowest floorSeminar

Car Park - Geometry• Sprinklers activatedSeminar

Car Park - Sprinklers• Close-up of sprinklersSeminar

Car Park - Sprinklers• Close-up of sprinklersSeminar

Car Park - TemperatureSeminar• This slide shows the temperature contours in a plane near thefire after 400s.• The high temperatures are mainly on the floor with the fire.

Car Park - Visibility• Sight length after 400s. This is the distance you can see. 30m isassumed to be infinitely far.Seminar• The visibility near the fire is poor,

PHOENICS applied to Steady-stateSimulations of the Internal Flowwithin a Multi-storey BuildingSeminar

IntroductionSeminar• CHAM’s Consultancy Team used PHOENICS/FLAIRfor the analysis of a multi-storey building in the Kistaregion of Stockholm, Sweden.• A model was created for testing the internaltemperature distribution when subjected to worstcasewinter and summer conditions (i.e. very cold orvery hot).

IntroductionSeminar• There was concern about:– the production of colddowndrafts in the atrium oralong the large glassedfaçades during the winter– whether there were regionsof unacceptably high airtemperature during thesummer time.

IntroductionSeminar• The building design was supplied in the form of anumber of AutoCAD.DWG (Drawing) files of thebuilding and its location, along with the operationalboundary data, such as:– the glass specification,– the building material,– internal heat sources, together with an estimate of the numberof people, and supplementary heating and cooling baffles.

Geometry CreationSeminar• Eight offices are located on four floors on either sideof the atrium.• AC3D was used to create ‘bespoke’ objects for theoffice floor

Geometry CreationSeminar• Included within the model are some 650 objectsrepresenting doors, walls, roof, ceilings, glasswindows, computers, persons, office furniture andvarious types of heat-sources.• The distribution of these objects in all offices oneach floor is similar.

Geometry CreationSeminar• Once one floor had been created, the ‘Array Copy’feature was used to quickly generate the remainingfloors.

Problem SpecificationSeminar• To represent summertime conditions, a total solarheat gain of 46,580 Watts is specified through theglass doors and windows, with the radiationprojected onto the floors and internal walls.• This is in addition to the normal heat generated bypeople in the conference room and offices, and bylights and machines inside the building.• The temperature within the building is regulated byan air conditioning system introducing cooled air at15°C, and a ventilation system generating a total airexchange of 2300 l/s throughout the building.

Problem SpecificationSeminar• The winter case differs in that there is no solar heataffecting the temperature in the building.• Due to the low temperature outside, the glass doorand all the glass windows take heat away from thebuilding.• The temperature of the ventilation air in the building isincreased from 15°C to 18°C.

ResultsSeminar• A total mesh size of 1.1M cells (108 * 123 * 85) wasused, non-uniformly distributed over the entirecalculation domain.

Results• A converged solution was obtained after 2000iterations, which took 22 hours to complete on a3MHz PC, and 8.5 hours on an equivalent 4-processor cluster using the parallel version ofPHOENICS.Seminar

Results• Summer temperatures – X planeSeminar

Results• Winter temperatures – X planeSeminar

Results• Summer temperatures – Y planeSeminar

Results• Winter temperatures – Y planeSeminar

Results• Velocities in one of the roomsSeminar

Results• Velocities in one of the roomsSeminar

Results• Temperatures in one of the roomsSeminar

Results• Temperatures in one of the roomsSeminar

ConclusionSeminar• These, and more-detailed, results were supplied tosupport evidence from CHAM’s customer todemonstrate the effectiveness of the building’sHVAC design under atypical weather scenarios.

PHOENICS Applied to Large-scaleEnvironmental FlowsSeminar

Large-scale EnvironmentalFlowsSeminar• The work concerns localised environmental conditionswhich could affect the occupants of the buildings aswell as pedestrians.

Large-scale EnvironmentalFlows• The objectives of this project are:Seminar– to investigate the influence of different wind speeds andwind directions on the air flow throughout the residentialarea;– to reveal any unusual wind patterns that may cause suctionand up- and down-drafts that could render podium, balcony,penthouse or terraced areas at lower or upper levelsdangerous to the residents.

Large-scale EnvironmentalFlowsSeminar• In the past, such an investigation would have required:– the construction of a small-scale model of the proposedcomplex of buildings,– placing the model in a wind-tunnel, and– making extensive measurements.• Nowadays, use of simulation techniques enables thesame information to be obtained more swiftly, and atsmaller financial cost.• CHAM has therefore employed its proprietary softwarepackage, PHOENICS-FLAIR, to evaluate theaerodynamic implications of the CAD-filerepresentation of the Residential complex supplied bythe client.

Large-scale EnvironmentalFlowsSeminar• In the first stage of the work, reported here, thecomplex has been studied as a whole, in order that theinfluences of one building on another can be includedin the prediction.• In later stages it is proposed to study in finer detailsuch individual buildings, and parts of buildings, as thefirst-stage study has shown to deserve furtherattention.

Large-scale EnvironmentalFlows• Geometry and calculation domainSeminar– The calculation domain covers the entire area of 2939m x1300m, provided by the Client in a single geometry file,including all the buildings and surrounding areas.– The height of 302m from the ground in the vertical direction ofthe calculation domain provides about 100m open spaceabove the tallest building.

Large-scale EnvironmentalFlows• Physical modellingSeminar– Three-dimensional conservation equations are solved formass continuity and momentum.– The flow is steady.– The Cartesian co-ordinate system is employed. A non-uniformmesh distribution is adopted with finer meshes assignedaround the buildings.– The grid used uses 208 x 167 X 46 cells.– Ground friction is considered.– The turbulence is represented by the LVEL turbulence modelbuilt into PHOENICS.

Large-scale EnvironmentalFlows• Boundary conditionsSeminar– A wind profile of U 1/7 with the measured wind speed at aheight of 8m is employed at the boundaries where the windenters the domain.– In-Form is used to set the boundary layer profile.

Large-scale EnvironmentalFlowsSeminar• The results show thatthe predicted localisedwind speed increases asthe incoming wind speedincreases and as theheight from the groundincreases.• The maximum windspeed could reachover 200 kph.

Large-scale EnvironmentalFlowsSeminar• In-Form was used to deduce the velocity in kph fromthe standard PHOENICS m/s.

The Use and Application ofCFD in the Air ConditioningSeminarand Fire Protection IndustryAIRAH NSW February 2008