CFD Modelling of Indoor Air Quality and Thermal Comfort

Transcription

1 Proceedings of he nd IASME / WSEAS Inernaional Conference on Coninm Mechanics (CM'07), Pororo, Sloenia, Ma 5-7, 007 CFD Modelling of Indoor Air Qali and Thermal Comfor LÁSZLÓ KAJTÁR ANITA LEITNER Dearmen of Bilding Serice Engineering Bdaes Uniersi of Technolog and Economics H- Bdaes, Mőegeem r. 9 HUNGARY ajar@ege.bme.h Absrac: Gaseos emission - CO, NO, and NO of gas soe has significan and harmfl effec on indoor air qali (IAQ) in residenial ichens. To aoid increasing healh ris i is essenial o se mechanical enilaion sch as ichen hood. Hoeer, according former laboraor sdies, ehas air flo generaed b ical hoods is no adeqae o achiee reqired IAQ. In order o describe reqired enilaion of ichens, emission of gas soes has been inesigaed for ears a Dearmen of Bilding Serice Engineering, BUTE. Laboraor and field sdies ere carried o, aferards, based on he resls, ollan disribion as described b CFD simlaion (FLOVENT). In his aer an oerie of mehod and resls of CFD modelling is blished. Ke-ords: IAQ, CFD modelling, ichen enilaion, CO, NO, Inrodcion Gaseos emission - CO, NO, and NO of gas soe has significan and harmfl effec on indoor air qali (IAQ) in residenial ichens. Former laboraor sdies hae shon ha o roide adeqae indoor air qali significan higher sl airflo is reqired han o ensre brning rocess []. Considering he comlei of describing eqaions CFD model shold be sed o redic indoor air qali and concenraion disribion. Based on resls of comaional inesigaions reqired sl airflo can be esimaed ih resec of IAQ reqiremens. Mehods Model resened in his aer can be alied in he folloing case: Mechanical enilaion is roided b ichen ehas enilaion, insalled aboe he soe. Room air recirclaion is no feasible. Gaseos emission of soe consiss of carbon dioide, niric oide and nirogen dioide. Using he model concenraion disribion in he ichen can be rediced and reqired enilaion can be esimaed. Chemical ollion loads (CO, NO, NO ) of soes hae been measred in IAQ laboraor of Dearmen of Bilding Serice Engineering, BUTE. As measring loads, mechanical enilaion did no oerae, air echange as roided onl b naral filraion. To carr on frher calclaion filraion echange rae had been measred beforehand [].. Describing eqaions Resls of CFD models are based on solions of Naier-Soes eqaions, he energ eqaion, he mass and concenraion eqaions as ell as he ransor eqaions for rblen eloci and is scale [4]... Conseraion of mass In case of rblen flo, eloci can be esimaed as a sm of a ime-mean and a flcaing comonen: ; ; ; () Considering in δ ime ineral ; ; ; eqaion () become: Concenraion disribion can be rediced based ollan emission and alied enilaion ssem. ( ) ( ) ( ) 0 ()

2 .. Naier-Soes eqaion Saic ressre can be described as a sm of a imemean and a flcaing comonen as ell ( ). Considering, and coordinaes, folloing eqaions are: direcion: ( ) ( ) ( ) g () direcion: ( ) ( ) ( ) g (4) direcion: ( ) ( ) ( ) g (5) The erms sed describe eloci flcaion in eqaions () (4) and (5) are he Renolds sress indees (ime-mean ale of eloci flcaion). To deerminae Renolds sresses roer rblence model shold be sed. Considering isenroic ( ) flo Renolds sresses can be calclaed based on rblence iscosi: (6) (7) here is he ineic energ of he rblen elociies: ( ) (8) Based on -ε rblence iscosi model: ε C (9) here C (0.09) is an emirical consan, moreoer ε is he dissiaion rae of mean rblen iscosi... Conseraion of hermal energ The conseraion of hermal energ in he conrol olme is: Γ Γ Γ (0) here σ Γ ; and arameer σ is deend on Prandl and Schmid nmbers...4 Conseraion of mass In eqaion reresen conseraion of mass G ɺ is he chemical load (for inesigaed ollan): Proceedings of he nd IASME / WSEAS Inernaional Conference on Coninm Mechanics (CM'07), Pororo, Sloenia, Ma 5-7, 007

3 Proceedings of he nd IASME / WSEAS Inernaional Conference on Coninm Mechanics (CM'07), Pororo, Sloenia, Ma 5-7, 007 ( c) ( c) ( c) ( c) Γ Γ Γ ( c ) ( c ) ( c ) Gɺ Pollion loads hae been esimaed b laboraor measremens. () (4) Defining he inesigaed henomenon frher condiion shold be gien o describe e.g.: iniial circmsances. Iniial and definie condiions: ( 0) 0 C Gɺ 0 c(0,,,) c c sfi i..4 Vɺ Vɺ odoor sl fil 0 consan consan consan sl 0 indoor ( 0) 0 consan Bondar condiions: A sfi i..4 α * (,,,) [ ( ) ( ) ] sfi f Θ(,,,) i i..4 cθ Vɺ d indoor 0; 0 90 da V cθdv (,,,) indoor () () CFD model To esimae reqired ehas air flo CFD modelling has been made b FLOVENT. Nmber of cases has been inesigaed as regards amon of air remoed b ichen hood. Sl air has been roided sing air erminal deices insalled aboe he indos. Validi of CFD model has been inesigaed based on resls of former laboraor and filed sdies.. Modelling consideraions Geomerical model has deeloed according archiecral arameers of enclosre inesigaed a field sdies. Gas soe model (P5W) has been made folloing roorions of a deice ih aerage echnical arameers, herefore commonl sed one. Figre. Plan of model ichen (V room 9,5 m ) Air flo eraced b hood (h 80 cm) Brner oer P5W Sl air erminal deice Pollion load (5) G CO,80*0-4 g/s G NO,48*0-8 g/s G NO 7,80*0-8 g/s 0 m /h - 60 m /h 60 m /h 80 m /h 90 m /h 50 m /h 5 m /h 500 m /h 4 5 m /h Table. Inesigaed ichen enilaion ssems Thermal roeries of soe hae been sdied b measring air emerare and air eloci arond he oring soe a 0 oins and srface emerare. To describe effec of increasing srface emerare aroimae fncions hae been deeloed based on measremens resls. To describe ime deending arameers ime-se(s) has o be esimaed. Toal ransien eriod (60min) has been diided ino folloing ses: min, 5min, 0min, 5min, 0min, 0min, 45min and 60min. Daa saed a 0h, 0h and 60h mines. To model ichen hood fied flo elemen has been sed in sie 60 5 cm, ih 45% free area raio. Sl air erminal nis hae been described in a similar a. Each diffser (4 50cm, ih 50% free area raio) is laced aboe he indos (no more han o for one indo). Ehas and sl airflos in eer inesigaed siaions see in Table. 4 Resls In folloing Figres resls from a seleced lane are resened. Considering eeced osiion of occans, arameers hae been folloed a 0 monior oins laced in fron of he sae, a.5m high along he cenreline of he brner, in eer 0cm.

4 Proceedings of he nd IASME / WSEAS Inernaional Conference on Coninm Mechanics (CM'07), Pororo, Sloenia, Ma 5-7, Hereb concenraion (CO, NO, NO ) disribion, indoor air emerare and mean air eloci are blished a V ɺ e 0 and a V ɺ e 80 m /h airflo in 0mines afer rn on he soe (mechanical enilaion sar a same ime). Figre 5. Indoor air emerare (0min, V ɺ 0 m /h); Kajár-Leiner (006) e Figre. CO concenraion (0min, V e 0 m /h); Kajár-Leiner (006) Figre. NO concenraion (0min, V ɺ 0 m /h); Kajár-Leiner (006) e Figre 6. Indoor air emerare (0min, V ɺ 0 m /h); Kajár-Leiner (006) e Figre 4. NO concenraion (0min, V ɺ 0 m /h) Kajár-Leiner (006) e Figre 7. CO concenraion (0min, V ɺ 80 m /h); Kajár-Leiner (006) e

5 Proceedings of he nd IASME / WSEAS Inernaional Conference on Coninm Mechanics (CM'07), Pororo, Sloenia, Ma 5-7, Figre 8. NO concenraion (0min, V ɺ 80 m /h); Kajár-Leiner (006) e Figre. Indoor air emerare (0min, V ɺ 80 m /h); Kajár-Leiner (006) e Figre 9. NO concenraion (0min, V ɺ 80 m /h) Kajár-Leiner (006) e Figre 0. Indoor air emerare (0min, V ɺ 80 m /h); Kajár-Leiner (006) e 5 Conclsions Based on resls folloing conclsions can be made: Reqiremens for nirogen-oides (NO ) concenraion can no o be roided ih reasonable ehas airflo. Reqiremens for carbon-dioide concenraion can be flfilled ih 60 m /h ehas airflo. To me IAQ reqiremens considerabl higher enilaion rae shold be roided. According calclaed resls, aroimael 4,7 m /h airflo i is sfficien o ensre brning rocess of naral gas. Smbols and nis: V ɺ [m /h] sl airflo sl V ɺ e [m /h] ehas airflo V ɺ fil [m /h] naral filraion n [h - ] air change rae G ɺ [mg/h] chemical ollion load c [g/m ] indoor concenraion c odoor [g/m ] odoor concenraion sfi [ o C] srface emerare of he soe indoor [ o C] indoor air emerare odoor [ o C] odoor air emerare Θ [K] oer emerare,, [m/s] indoor air eloci ecors [min] ime [Pa] saic ressre c [J/gK] calorific ale [g/m ] densi [gm/s] dnamic iscosi ν [m /s] inemaical iscosi [gm/s] rblence iscosi

6 Proceedings of he nd IASME / WSEAS Inernaional Conference on Coninm Mechanics (CM'07), Pororo, Sloenia, Ma 5-7, References: [] Kajár L.-Leiner A.-Bánhidi L.:Ealaion of IAQ in Residenial KichensBased on Laboraor and Field Sdies Lisboa, 006. jn. 4-8.,HB 006. h Inernaional Conference on Healh Bildings Proceedings Volme V. -6. [] Kajár L.- Leiner A. Bánhidi L.-.: Air qali and hermal comfor in ichens. Beijing, China, 005. Se h Inernaional Conference on Indoor Air Qali and Climae Proceedings Volme II/ [] Dr. Kajár Lásló - Leiner Ania: Effec of gas-range on air qali of liing saces ROOMVENT004; 9h Inernaional Conference Uniersi of Coimbra / Porgal; Boo of Absracs 6-7 [4] H. B. Abi: Venilaion of bildings, London. 998 E & FN Son [5] Garbai L.-Némehi B.: A éülegéése domános roblémái Magar Éülegéése 49/, 000., -4. [6] Bánhidi L. - Kajár L.:Komforelméle. B, 000. Egeemi Tanön, Mőegeemi Kiadó 46.