Energy and Buildings 43 (2011) 27602766

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Airow and heat transfer in double skin facades

Teshome 2

a Mechanical E D 212b Mechanical a , Unitc Building, Civi st, Mo

a r t i c l

Article history:Received 21 MReceived in reAccepted 23 Ju

Keywords:ComputationaDouble-skin faSurface heat trEnergy efcien

wasCFD)FD p

ped wel ar

encehe ai(outepare

1. Introdu

Double-of two glassdevices placed within the cavity. The ventilated cavity functionsas a thermal buffer by reducing undesired heat gain during thecooling season, heat loss during the heating season and thermaldiscomfort due to asymmetric thermal radiation. DSFs also play animportant role in glare control and maximization of day lightingthrough pro

The facaponent of tsuch as solor indirectltemperatursuch doubloptical chaenhanced bthe openingnatural andon the typeDSF cavity cfor natural vThe airow

CorresponE-mail ad

haghi@bcee.co1 Tel.: +1 942 Tel.: +1 51

ndsoparof tht the

Experimental and numerical models have been used for study-ing the performance and optimization of DSFs. Models that havebeen used for the prediction and analysis of the performance ofDSFs include analytical and lumped models [2], dimensional anal-ysis [3], network models [4], zonal models [5] and airow network

0378-7788/$ doi:10.1016/j.per positioning of shading devices.de systems of commercial buildings are the main com-he building envelope that receives external heat gainsar irradiance transmitted directly through the facadey as secondary heat ux from absorbed irradiance. Thee increase throughabsorptionon shadingdevices insidee facades depends on air volume ow rates and theracteristics. The energy efciency of the DSFs can bey controlling the slat angle of the shading device ands for supplying air to and exhausting from the cavity formixed mode ventilation. DSFs can be classied basedof ventilation and construction. The ventilation of thean be either natural ormechanical [1]. The driving forceentilation is either thermal buoyancy orwind pressure.is therefore not easy to control nor is it continuous since

ding author. Tel.: +1 410 455 4779/3553; fax: +1 410 455 1052.dresses: tejiru@umbc.edu (T.E. Jiru), yong.tao@unt.edu (Y.-X. Tao),ncordia.ca (F. Haghighat).0 565 2400; fax: +1 940 369 8675.4 848 2424x3192; fax: +1 514 848 7965.

models coupledwith energy simulation [6,7]. Detailed studies havealso been conducted using computational uid dynamics (CFD) andexperiment for mechanically ventilated facades [8], for naturallyventilated facades [9] and for naturally ventilated facades equippedwith venetian blinds [10]. Gratia and De Herde [11] evaluated theinuence of the shading device position and color within a doublefacade on the summer cooling using thermal simulation software.Cooling energy reductions of 13.514.1% were predicted when theblind was moved from a position close to the inner glazing to thecentre of the cavity. Other similar studies have also been conducted[12,13].

The objective of this study is to model and simulate the airowand heat transfer phenomena in the DSF system using CFD tech-nique and study the inuence of the location of the blinds and theslat angle on the temperature and air distribution in the air cavityand on the glass surfaces.

2. Case description

Thecase selected for thedevelopmentandvericationof theDSFmodels is an experimental test cell from Jiru andHaghighat [5]. The

see front matter 2011 Elsevier B.V. All rights reserved.enbuild.2011.06.038Edae Jirua,, Yong-X. Taob,1, Fariborz Haghighatc,

ngineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Mnd Energy Engineering, University of North Texas, 3940 North Elm St, Denton, TX 76207l and Environmental Engineering, Concordia University, 1455 de Maisonneuve Blvd. We

e i n f o

arch 2011vised form 4 June 2011ne 2011

l uid dynamicscadesansfer coefcientscy

a b s t r a c t

Airow and heat transfer simulationusing computational uid dynamics (slat tilt angle and blind position. The Ca mechanically ventilated DSF equipsurface temperatures of the CFD modpresent study indicates that the prescients (SHTCs), the temperature and tchanges in the position of the blindstemperature, velocity, and SHTCs com

ction

skin facades (DSFs) are building envelopes comprisedes, a ventilated air cavity in between and solar control

it depeusuallysystemexhaus/ locate /enbui ld

50, United Statesed Statesntral, Qubec, Canada H3G 1M8

conducted for a DSF system equipped with a venetian blind,with RNG turbulence model, for a three-level combination ofrediction was validated using experimental data collected forith venetian blinds. The predicted trends in glass and blinde compared well with the experimental measurements. Theof venetian blinds inuences the surface heat transfer coef-r distribution in the DSF system. For the cases considered, ther, middle, and inner) have more effect on the distribution ofd to the changes in the slat angles ( =0, 45, 90).

2011 Elsevier B.V. All rights reserved.

n theweather condition.Mechanically ventilatedDSF ist of the heating ventilation and air conditioning (HVAC)e building. It can be used to pre-heat the outdoor air orindoor air.

T.E. Jiru et al. / Energy and Buildings 43 (2011) 27602766 2761

Nomenclature

CFD computational uid dynamicsCa1Ca2cpDSFsEkFkj

gIBHVACJkkL1L2L3L4MBOBpqin,k

qout,kqsolqtransShSk, SuiuISHTCsTToTexTindoorToutdoorTrefy

Greek symkeff

test cell is 2side of thewith an outFig. 1. The othick clear g15mmwidecavity betwinstalled inity into outeat 45 fromthe DSF cavinner layerof the DSF bmonitoringouter cavityinner cavityspecic heat capacitydouble skin facadesemissive power of a surface kfraction of energy leaving surface j that is incidenton surface kgravityinner blindsheating, ventilation and air conditioningradiosity of surface ksurfaceexterior glass of the double paneinterior glass of the double-pane

venetian blindsinterior glass of the ventilated DSFmiddle blindsouter blindspressureenergy ux incident on a surface from the surround-ingsradiosity of surface ktotal solar radiationtransmitted solar radiationvolumetric heat sourceuser-dened source termsvelocityuctuating velocitysurface heat transfer coefcientstemperatureair temperature at the inletair temperature at the exitroom air temperatureoutside air temperaturereference (inlet) temperaturedistance from a wall, vertical distance from the bot-tom of DSF

bolsabsorptancetransmittanceviscositydensity, reectancereectivity of surface kthermal conductivityeffective thermal conductivity

.5m high, 1.6m wide and, 3.6m long. The south facingcell, which was 1.6m wide and 2.5m high, has a DSFer double-pane facade, and an inner facade as shown inuter double-pane facade, L1 and L2 are 8mm and 6mmlasses, respectively. The air cavity between L1 and L2 is. The internal pane (L4) is 6mmthick clear glass. The aireen L2 and L4 is 15 cm wide. A venetian blind (L3) wasthe air cavity between L2 and L4 and divides the air cav-r (Ca1) and inner (Ca2) cavities. The slats were inclinedthe horizontal. The air from the test cells entered intoities through an opening located at the bottom of the(L4), as shown in Fig. 1, and was extracted at the topy a fan. The test cell was equipped with a continuoussystem tomeasure the energy consumption, the indoor

Fig. 1. A mechis the interiorglassof thevenair temperatuair temperatuqtrans is the tra

air temperaature distrithe airow0.4 cm, 1.35

The meathe exhaustdoor, indooare shownstudy usedmaximum icorrespondtion values

A paramof the slat aair cavity: oposition ofof blinds an

Fanically ventilated DSF. L1 is the exterior glass of the double pane; L2glass of the double-pane; L3 is the venetian blinds; L4 is the interiortilatedDSF;Ca1 is theouter cavity; andCa2 is the inner cavity,To is the

re at the inlet, Tex is the air temperature at the exit, Tindoor is the roomre, Toutdoor the outside air temperature, qsol is the total solar radiation,nsmitted solar radiation, is thermocouple and is pyranometer [5].

tures, the heat uxes through the facade, the temper-butions in the air gap and on the facade surfaces, andrate. The sensors in the DSF system were positioned atm, and 2.3m from the oor as shown in Fig. 1.sured average volumetric ow rate at the outlet due tofan is 54m3/h. The measured total solar radiation, out-r and inlet temperatures measured on April 23, 2005in Fig. 2. The steady-state simulation conducted in thisthe maximum outdoor temperature of 17 C and thendoor temperature of 20 C as boundary conditions. Theing maximum inlet temperature and total solar radia-

were 20 C and 275W/m2 respectively.etric studywas also conducted to identify the inuencengle ( =0, 45, 90) and the position of the blind in theuter (OB), middle (MB), and inner (IB). Fig. 3 shows thethe blinds and the slat angle. Table 1 gives the locationd the slat angles used in the parametric study.

ig. 2. The measured inlet and boundary conditions [5].

2762 T.E. Jiru et al. / Energy and Buildings 43 (2011) 27602766

3. Modelin

A CFD aairow andservation oow resultsequations.

uixi

ujuixj

=

The aiructuatingis ReynoldsReynolds stmodeled inthe Boussinthe mean vstudy, has bclass of owthe air in th

t(cpT) +

The thermothe air denmation. Thepressure an

Table 1Cases for para

Slat angle (

Blind positio

atures. In glass facades and blinds, the conduction heat transferequation can be given as:

xj

(

T

xj

)+ Sh = 0 (4)

The volumwhich is giv(L1, L2, and

The thers w. Thefacerface eme reons.y emndethenurfa

Ek +oun

adirectorn surnship

Nj=1

F

ore, t

Ek +

inleed usdel edoorand

y bo) andFig. 3. Location and dimension of a blind slat [5].

g and simulation

pproach was employed to model and simulate theheat transfer in the DSF system. The application of con-f mass and momentum to an incompressible laminarin the continuity and the momentum (NavierStokes)

(1)

p

xi+

xj

(

uixj

)+ gi (2)

ow in the DSF air cavity is turbulent involvingmean andvelocity elds. One approach of modeling turbulenceaveraging. This method introduces additional term,

resses uiu

j, in the governing equations that need to be

order to achieve a closure. A common method employs

surfacemodelthe surgray sulaw, thface, thdirectidirectlis depewhichother s

qout,k =The amface isview fadent orelatio

qin,k =

Theref

qout,k =

Thespecithe moand inditionsvelocitand L4esq hypothesis [14] to relate the Reynolds stresses toelocity gradients. The RNG k- model, selected for thiseen found to be more accurate and reliable for a widers than the standard k- model. The energy equation fore cavity has the following form.

xj(uicpT)=

xj

(eff

T

xj

)+ Sh (3)

-physical properties are assumed constant except forsity, which is treated using the Boussinesq approxi-air properties are evaluated at standard atmosphericd at the average of the indoor and outdoor temper-

metric study.

) 0 45 90

n OB(x=1.87 cm)

MB(x=7.5 cm)

IB(x=1.31 cm)

Noblinds

(see Fig. 1)Many co

surface heaspeed measvalue of 29was used [1the surfacewas calcula[18]. The stional domin the Fluen

The cavithe top thecondition wmeasured vtemperaturat a zero galso the meturbulent kon the turb

The twobulent owetric source term Sh is the absorbed solar radiation,en by the absorptances and the thicknesses of glassesL4) and blinds (L3).mal radiation heat transfer between glasses and blindas calculated using surface-to-surface (S2S) radiationS2S radiation model employed for this study assumess to be gray and diffuse. Emissivity and absorptivity of ae are independent of the wavelength. Also, by Kirchoffsissivity equals the absorptivity and for a diffuse sur-

ectivity is independent of the outgoing (or incoming)The energy ux leaving a given surface is composed ofitted and reected energy. The reected energy uxnt on the incident energy ux from the surroundings,can be expressed in terms of the energy ux leaving allces. The energy reected from surface k is given as

kqin,k (5)

t of incident energy upon a surface from another sur-ct functionof the surface-to-surfaceview factor, Fjk. TheFjk is the fraction of energy leaving surface k that is inci-face j. For N surfaces, using the view factor reciprocity, qin,k yields:

kjqout,j (6)

he energy that is given off (radiosity) of surface k is

k

Nj=1

Fkjqout,j (7)

t, outlet as well as the wall boundary condition wereing the measured data (Fig. 2) for numerical solution ofquations. The maximum outdoor temperature of 17 C,temperature of 20 C were used as the boundary con-a temperature of 20 C as inlet condition. The no slip

undary conditions at the surface of all layers (L1, L2, L3,adiabatic boundary conditions at the bottom surface

were assumed.rrelations have been proposedwhich relate the outsidet transfer coefcient with wind speed. Since no windurement was taken near the site of the DSF, a standardW/m2 K, which corresponds to wind speed of 6.7m/s6]. On the side of the inner layer (L4) facing the indoors,heat transfer coefcient has a value of 8W/m2 K, whichted using empirical relation from ASHRAE handbookurface heat transfer coefcients within the computa-ain were calculated using the algorithms implementedt 6.3 code [15].ty air is extracted from cavities through an exhaust atDSF (as shown in Fig. 1) by a fan. Therefore, the outletas modeled as ow boundary and specied using theolumetric ow rate of 54m3/h and a measured exhauste of 25 C. The boundary condition at the inlet was setauge pressure and a temperature of 20 C, which wasasured average indoor temperature. The values of theinetic energy and is dissipation rate at the inlet dependulence intensity, length scale and inlet velocity [10].-dimensional governing equations which model tur-and heat transfer, in the DSF system, were solved

T.E. Jiru et al. / Energy and Buildings 43 (2011) 27602766 2763

Fig. 4. Comparison of the measured and calculated temperature in the outer (Ca1)and inner (Ca2) facade cavities.

using FLUENTs pressure-based solver. The simulation were rstrun without the S2S radiation model until convergence using rst-order upwind discretization and then second-order discretizationfor the convtion. Secondconvergencrestarted wrelationshipmass consepressure-veequationswless than th

4. Results

4.1. Validat

The temcavity (Ca2)heating of tand the enethrough theinner glasscomfort in texperimentcal prolesdepicted inature of thethat of the itom of L4 (ventilating

Fig. 5. Compaand the inner

a) Temperature contour and (b) velocity vector plots in the DSF systemwitht the middle and =45 .

moves up the DSF cavity, its temperature increases and thiscationphenomena is capturedby theCFDprediction in Fig. 4.er, thepredicted temperature atCa13 is lower than thepre-temperature at Ca23. The discrepancy is the result of thee of lateral mixing, which could increase the temperature inter cavity at Ca13. The two-dimensional model developedstudy could not capture the three-dimensional effects suchral mixing (see also Fig. 6). Fig. 5 shows that the measuredrature at L32 is below the temperatures at L31 and L33.crepancy at L32 can be due tomeasurement error thanpre-. Figs. 4 and 5 show that although the CFD under-predictedperature, except for the blinds (L3), it follows the trend of

mental data.temperature contour in Fig. 6(a) showshigher temperaturesupper parts of the DSF than the lower parts. This is becausetransferred from the slats, which are at higher tempera-ection terms to increase the accuracy of the nal solu--order accuracy was used for the viscous terms. Aftere was reached for the second time, the simulation wasith the S2S model. The SIMPLE algorithm, which uses abetween velocity and pressure corrections to enforce

rvation and to obtain the pressure eld,was selected forlocity coupling. The continuity,momentumand energyeredeemedtohaveconvergedwhen the residualsweree specied value of 106.

and discussions

ion of the CFD simulation

perature distributions in the outer cavity (Ca1), inner, and venetian blinds (L3) are predicted so that the over-he DSF cavity and the venetian blinds can be controlledrgy exchanged is monitored as the ventilating air owscavity. Moreover, the temperature distribution in the

(L4) should be known for the evaluation of the thermalhe room. The CFD simulation resultwas validated usingal data for slat angle =45 described above. The verti-for the measured and CFD predicted temperatures areFigs. 4 and 5. The experimental data shows the temper-air in the outer cavity (Ca1) was always greater than

nner cavity (Ca2). This is because the inlet is at the bot-Fig. 1), and the resulting an uneven distribution of theair allows more ventilating air ow to Ca2 than Ca1. As

Fig. 6. (blinds a

the airstratiHowevdictedabsencthe ouin thisas latetempeThedisdictionthe temexperi

Theat theheat isrison of the measured and calculated temperature of the blinds (L3)glass (L4).

ture than thin temperaeffect, resusection. Theouter cavitydue to thelayer (L4) a

4.2. Parame

Parametof the slatair cavity:Fig. 7 showe glasses due to their higher absorptance. This increaseture also augments the upward ow due to buoyancylting higher velocities at the upper section than lowervector plot in Fig. 6(b) shows that air velocity in the(Ca1) is greater than that of the inner cavity. This is

lower temperature difference between the inner glassnd the blinds (L3) than L3 and L2.

tric study

ric study was also conducted to identify the inuenceangle ( =0, 45, 90) and position of the blind in theouter (OB), middle (MB), and inner (IB) (see Table 1).s qualitative comparison of the inuence of blind posi-

2764 T.E. Jiru et al. / Energy and Buildings 43 (2011) 27602766

Fig. 7. A qualitative comparison of the inuence of blind position and slat angle on the cavity temperature distribution.

tion and slaIn all casesglass surfaction away fthe no blintemperatur

As showand blinds athe ambientions, the tethe no blinfor each cagures alsotemperaturthey are lesThe lower tetion is probinner glasssurface (L4)it reduces has a buffer.comfort du

Fig. 8. HorizonW is cavity wi

er. Thhiche coplicatem

L4) annerase rer thf thends a. 125m)etricaraturMB

(Ca2This rn thein sthemt angle on cavity temperature distribution in the cavity.the blind surfaces have higher temperatures than thees and the air in the cavity. The temperature distribu-rom the blinds is uniform and close in value to that ofd case. The blind position has more inuence on thee distribution than the slat angle.n in Figs. 810, the surface temperatures of the glazingre increased due to the solar heat gains compared witht (17 C) and indoor (20 C). For MB and IB blind posi-mperature away from the surfaces is close in value tods case or to the indoor temperature. The peak valuesse in the gures are at the position of the blinds. Theshow that although there are changes in the values ofe in the cavities due to the changes in the slat angle,s signicant compared to the change in blind position.mperature forMBposition shows that themiddle posi-ably suitable in providing a lower temperature on thesurface (L4). The high temperature on the inner glassfor IB cases could be desirable for winter conditions aseat transfer from the indoors and the cavity air servesSpecically for the IB position, it can create thermal dis-

summ(IB), wever, thDSF ap

Thelayer (of the iblind cis higheffect oThe bli

Figs(y=1.2symmtempeFor thecavity(Ca2).ature ichangetion ofe to radiation asymmetry and increases cooling load in

tal temperature prole in the air cavity at y=1.25mand =0 , wheredth.

Fig. 9. Horizowhere W is caemiddleposition (MB)worksbetter than innerpositioncan be mitigated by increasing the airow rate. How-st of running the fan has to justify energy saving due totion.perature distributions on the surface of the inner glassre depicted in Fig. 11. As stated above, the temperatureglass surface is highest for IB position. Although the noesulted in the lowest temperature distribution on L4, itan outside temperature (17 C), indicating the bufferingDSF system and a reduction of heat loss during winter.re however required for reducing the solar load.14 illustrate the velocity distribution at themid-heightof the DSF. The velocity distribution is not exactlyl even when there is no blind, which shows that thee distribution has inuenced the airow distribution.and OB positions, the highest velocity is in the outer), whereas for IB higher velocity is in the inner cavityesult corresponds to the location of the highest temper-horizontal temperature distributions in Figs. 810. Thelat angle slightly moves the prole curves and the loca-aximumvelocity. This again indicates that the changesntal temperature prole in the air cavity at y=1.25m and =45 ,vity width.

T.E. Jiru et al. / Energy and Buildings 43 (2011) 27602766 2765

Fig. 10. Horizontal temperature prole in the air cavity at y=1.25m and =90 ,where W is cavity width.

Fig. 11. Tempof the DSF.

in the positcavities mo

The variglass layerin Figs. 15 aangle havethe changesfrom 0 toOB (Fig. 15)IB positionin more turFurthermor

Fig. 12.

Fig. 13. Velocity prole in the cavity at 1.25m (mid height) and =45 .

. 14.Figerature distributions on the inner glass surface (L4), where H is height

ion of the blinds affected the air velocity prole in there that the changes in slat angle.ations of the surface heat transfer coefcient (SHTC) onL2 (x=0) and on glass layer L4 (x=0.15m) are shownnd 16. It can be observed that the changes in the slatless effect on the heat transfer coefcient compared toin the blind location when the slat angle is increased

45. The SHTC on L2 is highest when the blinds are atand the SHTC on L4 is highest when the blinds are at

(Fig. 16). The closeness of the blind to the layer resultsbulence on the surfaces and hence an increase in SHTC.e, the SHTC at L2 for the 90-OB case is lower than 45-OB

Velocity prole in the cavity at 1.25m (mid height) and =0 .

and 0-OB clower thanfor the 90-O(Fig. 15), an0-OB, 45-Mthat, althouis divided iwhen the slL2 increasesurface tem

The resublinds inubution in tthe changeimportant tVelocity prole in the cavity at 1.25m (mid height) and =45 .

ases (Fig. 15), and the SHTC at L4 for the 90-IB case is45-IB and 0-IB cases (Fig. 16). However, the SHTC at L2

B case is higher than 0-MB, 0-IB, 45-MB and 45-IB casesd the SHTC at L4 for the 90-IB case is higher than 0-MB,B and 45-OB cases (Fig. 16). These differences indicategh the slats completely are closed and the air cavitynto two cavities (Ca1 and Ca2) with very little airowat angle is 90, the closeness of the blind to either L1 ord the SHTC. Additionally, due to the differences in theperatures, the SHTCs at L2 and L4 are not equal.lts in this study indicate that the presence of venetianences the SHTCs, the temperature and the air distri-he DSF system. Specically, for the cases considered,s in the position of the blinds (OB, MB, and IB) is morehan the changes in slat angles ( =0, 45, 90). When

Fig. 15. SHTC on the second glass layer (L2).

2766 T.E. Jiru et al. / Energy and Buildings 43 (2011) 27602766

Fig. 16. SHTC on the inner glass layer (L4).

the blinds (L3) are positioned close to the glass surfaces (L2 andL4) the turbulent boundary layer caused by the blinds (L3) over-lap with the thermal boundary layer of the glass surfaces (L2 andL3) and heat transfer enhancement was obtained (Figs. 15 and 16).Similar results, using two-dimensional CFD models, for other typeof windows where the blinds are very close to the glazing lay-ers were obtained by Shahid and Naylor [18]. For larger cavitywidth (0.55m), Ji et al. [17] showed that the presence of venetianblinds at oeffect on thnot close eary layers.due to the seffects suchof heat tradetailed thraccurate prperature, vtrend of thein Figs. 91

5. Conclus

Althougtions of the

cavity air, glass, and blind surface temperatures predicted usingthe two-dimensional CFD model followed the trend of experimen-tal data. The CFD simulation results showed that the presence ofvenetian blinds inuences the SHTCs, the temperature and the airdistribution in the DSF system. Specically, for the cases consid-ered, the changes in the position of the blinds (OB, MB, and IB)affect the SHTCs, the airow and temperature distribution than thechanges in the slat angles ( =0, 45, 90).

References

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[3] C. Balocco, A non-dimensional analysis of a ventilated double facade energyperformance , Energy and Buildings 36 (2004) 3540.

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[10] N. Safer, M. Woloszyn, J.J. Roux, Three-dimensional simulation with a CFD toolhe airow phenomena in single oor double-skin facade equipped withetian blind , Solar Energy 79 (2005) 193203.ratia, A.DeHerde, Themost efcientpositionof shadingdevices in adouble-n facaicker,uildinaggemaviou(2003Hinzeent, FlRAE,ditioni, M.J.ble-s, 200hahidntal vene-third of the cavity width does not impose a greate SHTCs because the glass surfaces and the blinds arenough to cause interaction of their turbulent bound-The discrepancies of the two-dimensional could beimplications in the geometry, the three-dimensionalas reverse ow and local short circuiting, the effect

nsfer through the frames and experimental errors. Aee-dimensionalmodel of the DSF system can givemoreediction by changing the predicted values of the tem-elocity, and SHTC without signicantly changing thetemperature, velocity, and SHTC distributions shown

6.

ion

h there were discrepancies in the quantitative predic-CFD model when compared with the experiments, the

of tven

[11] E.Gski

[12] U. Eof b

[13] D. Fbeh75

[14] J.O.[15] Flu[16] ASH

con[17] Y. J

doution

[18] H. Sizode , Energy and Buildings 39 (2007) 364373.V. Fuxa, U. Bauer, L. Mei, D. Ineld, Facades and summer performancegs , Energy and Buildings 40 (2008) 600611.bauu, M. Costa, M. Soria, A. Oliva, Numerical analysis of the thermal

r of glazed ventilated facades inMediterranean climates , Solar Energy) 229239., Turbulence , McGraw-Hill Publishing Co., New York, 1975.uent 6.3 Users Guide , Fluent Inc., NH, USA, 2006.Fundamentals, American Society of Heating , Refrigeration and Air-ing Engineers, Atlanta, GA, 2009.Cook, V.I. Hanby, D.G. Ineld, D.L. Loveday, L. Mei, CFD Modeling ofkin facades with venetian blinds , in: Proceedings of Building Simula-7, pp. 14911498., D. Naylor, Energy performance assessment of a window with a hor-netian blind , Energy and Buildings 37 (2005) 836843.

Airflow and heat transfer in double skin facades1 Introduction2 Case description3 Modeling and simulation4 Results and discussions4.1 Validation of the CFD simulation4.2 Parametric study

5 ConclusionReferences