Air Age Equation Parameterized by Ventilation Grouped Time WU Wen-zhong

Transcription

1 Appled Mechancs and Materals Submtted: ISSN: , Vols , pp Accepted: do: / Onlne: Trans Tech Publcatons, Swtzerland Ar Age Equaton Parameterzed by Ventlaton Grouped Tme WU Wen-zhong X an Unversty of Scence and Technology, Chna E-mal: wuwenzhong@tju.edu.cn Keywords: ; IAQ; grouped tme parameter; ar age; equaton Abstract. Ventlaton temperature-velocty-temperature gradent grouped tme parameter and these parameterzed ar age equaton are constructed to calculate ar age, not only of a sngle but also of s more than one type, combnng wth the celebrated average ar age equaton, based on study of and ar age at a certan subway staton platform n ths paper. These new results meet well wth those of Arpak smulated, whch shows a new complete method to calculate ar age by the average ar age equaton, and broaden the ar qualty audt theory n sde of ar age. Introducton Indoor ar qualty (IAQ) s affected by CO 2 concentraton, surplus heat or humlty, pollutants, such as smoke of fre. Ventlaton controls temperature, ar velocty and pressure, pollutant concentratons for a good IAQ [1].. Indexes for audtng IAQ compose of ar temperature, velocty and ar age, etc. [2-4], and among whch ar age, the tme taken by to reach a certan pont, beng representatve of local ar dstrbuton and freshness, s of mportance to check effectveness. In case of flows more than one, the average ar age equaton [3] s combned wth mass conservatve equaton etc. to solve local ar age. Based on measurement at a certan subway staton platform and the followng ar age smulatons, the author has analyzed that ar age s composed of moton tme, whch s called as ar flow moton theory of s at platform, and also concluded that: connected s n seres of celng, longtudnal and extract cut down ar age at central ponts wth a large proporton, and also vary those at other ponts, whch s expressed as optmzaton of ar flow dstrbuton can cut down local ar age [5-8]. Expandng these two results, ths study constructs temperature-velocty-temperature gradent grouped tme parameter, and also thus parameterzed ar age equaton, combned wth the average ar age equaton, to calculate ar age under dfferent condtons, whch agree well wth those smulated, therefore a new complete method for ar age calculaton has ganed, and broaden applcaton feld of ar age theory to audt ar qualty. Ventlaton measurements and ar age smulaton at a certan subway platform The dscussed platform, length 120 wdth 20.6 heght 12.5 m, s suppled fresh ar to ts hall and platform by two reversble propeller fans at rate 61 m 3 /s 2 n the state [9-11]. We measure ar veloctes n ths state at 40 Hz for summer case, 35 Hz for wnter case, wth ADM 860 C ar parameter test apparatus added an ar cover. 1.1 Ventlaton measurements. Ventlaton s measured n the subway runnng hours, as Tab.1, where NE1-NE20 are ar outlets No.1-No.20 at eastern sde of north half platform, SW1-SW19 are ar outlets No.1-No.19 at western sde of south half platform. All rghts reserved. No part of contents of ths paper may be reproduced or transmtted n any form or by any means wthout the wrtten permsson of Trans Tech Publcatons, (ID: , Pennsylvana State Unversty, Unversty Park, USA-10/05/16,06:13:19)

2 450 Sustanable Ctes Development and Envronment Protecton IV Table 1 Ar veloctes of ar outlets at platform ( m 3 /h ) outlet 35Hz 40 Hz outlet 35 Hz 40 Hz outlet 35 Hz 40 Hz outlet 35 Hz 40 Hz NE NW SE SW NE NW SE SW NE NW SE SW NE NW SE Ar age smulaton. The dscussed platform s modeled wth the measured data n Tab.1 and ts varatons of velocty, temperature or envronmental condton n order to smulate ar age n seven cases at those central ponts of platform by Arpak, wth default CO 2 concentraton, and temperature of envronment n summer 26.4, 28 on platform floor. The nputs and smulated ar ages are shown n Tab.2. Smulaton case Table 2 Celng velocty Ventlaton boundary condtons and local ar ages Celng temperature ( ) Longtudnal velocty (m/s) Longtudnal temperature ( ) Extracton velocty (m/s) Local ar age of central pont 1 measured measured measured measured 2, measured ~180 6 measured ~ ~45 7 measured ~ velocty record n a summer day, 2 data of 40Hz case n Table 1, 3 veloctes at central platform ncreased by 10~30% to data n Table 1, 4 envronmental temperature -5. Ar age equaton parameterzed by grouped tme The foregong measures and smulates control to IAQ, and the reason of whch s the called optmzaton of ar flow dstrbuton can cut down local ar age, therefore more nsght of ar flow moton may llumnate ways to gan good effectveness and IAQ at subway staton. 2.1 Ventlaton temperature-velocty-temperature gradent grouped tme. As shown n Tab.2, velocty, temperature are among factors of ar age, that s, ncreasng celng (case 2 and 5) or longtudnal (case 6) or extracton (case 7) velocty can decrease local ar age, and hgher temperature ncreases average ar age (case 3), whch s decreased by lower envronmental temperature (case 4). Generally, varous flows may be used to control IAQ, so denote - type, and the correspondng T, v, g -ts temperature ( o C ), velocty ( m s ) and temperature gradent ( o C m ),then construct temperature-velocty-temperature gradent grouped parameter as T = (1) v g t Obvously, ths parameter scales as tme, therefore we call t as temperature-velocty-temperature gradent grouped tme, or grouped tme for smplcty.

3 Appled Mechancs and Materals Vols Ar age equaton parameterzed by grouped tme. Suppose N types to control IAQ and audt by ndex ar age, the grouped tme of each t s calculated from Eq.(1), then the called ar flow moton theory of s at platform suggests the weghted ar age at pont A wth each weght k as τ N ( A) = k t (2) = 1 whch s ar age equaton parameterzed by grouped tme. By ths equaton, we can calculate ar age n most cases of varety, ncludng ar ages of a sngle and local ar age affected by s more than one type, therefore we come to complete predcton of ar age under any mode. Case study: ar age soluton wth combned equatons At smulated ar ages affected by celng, longtudnal and extracton 3 type s n Table 2, Eq.(2) expresses ar age at pont A wth N = 3 referrng to celng, longtudnal and extracton s. Calculate temperature gradents and ft weghts n Eq.(2) of 7 cases from Tabs.1-2, then solve local ar age affected by a sngle by combnaton of Eq.(2) to the average ar age equaton (refer to [3] Eq.(3)) as Tab.3, then add the known ar ages of a sngle as Eq.(2) to get local ar age affected by s more than one type. Smulaton case Table 3 Ar age of celng Ar ages of a sngle n 7 cases Ar age of longtudnal Ar age of extracton Table 3 shows that ar ages of both celng and longtudnal decrease nversely wth ncreasng velocty (cases 1-2 for celng, and cases 5-6 for longtudnal ), however, ncrease at hgher temperature (cases 2-3 for celng, and cases 3-4 for longtudnal ). All of these results of sngle agree well wth those n references [5-8]; Although extracton has smaller ar age than those of celng and longtudnal to 10 2, and contrbutes less to average ar age, t nduces more celng and longtudnal, and then as a result, cuts down ar ages of those two s (cases 7); Obvously, comparson of Tabs. 2 and 3 shows that ar age sum of 3 type s just calculated s not equal to the smulated average ar age n 3 type s case, the reason of whch s that ar age of dfferent type may weght dfferently n the average one, as Eq.(2), n other words, average ar age s the weghted ar age sum of s.

4 452 Sustanable Ctes Development and Envronment Protecton IV Conclusons Based on measurement at a certan subway staton platform and the followng ar age smulatons, wth applcaton of ar flow moton theory of s at platform and optmzaton of ar flow dstrbuton can cut down local ar age concept nto IAQ analyss at platform, ths paper (1) constructs temperature-velocty-temperature gradent grouped tme parameter, and also thus parameterzed ar age equaton, (2) then combnes the grouped tme parameterzed ar age equaton wth the average ar age equaton, and solves not only ar ages of a sngle, also those affected by s more than one type, (3) and dscusses ar ages of a sngle to show that ar ages of both celng and longtudnal decrease nversely wth ncreasng velocty, but ncrease at hgher temperature, whch agree well wth those exsted results; And extracton has small ar age, and also nduces more celng and longtudnal, and then as a result, cuts down ar ages of those two s; And addng ar age of sngle to get ther averaged ar age should lay weghts on each of them, n other words, average ar age of s s ther weghted ar age sum of each sngle. As the just shown, temperature-velocty-temperature gradent grouped tme parameter and thus parameterzed ar age equaton are a new method for ar age calculaton, not only of a sngle but also of s more than one type, therefore we come to complete predcton of ar age under any mode, and broaden theoretcal applcaton feld of ar age to audt IAQ. Supported by: Ph. Dr. Foundaton of X an Unversty of Scence and Technology (2011QDJ009), Correspondng Author: WU Wen-zhong (1968-), Engneer/Lecturer, nterested n HVAC, fre scence, appled mathmatcs. E-mal: wuwenzhong@tju.edu.cn. References [1] LI Xan-tng, SHI Wen-xng. Man-made envronment [M]. Bejng: Chna archtecture and ndustry press, 2006 (n Chnese). [2] L X T, L X F, Zhu Y X. The mathematcal modelng of ar age [C]// Proceedngs of the Internatonal Symposum on Ar Condtonng n Hgh Rse Buldngs 97, Shangha, Chna, 1997: [3] Xantng L, Dongnng L, Xudong Yang, et al. Total ar age: an extenson of the ar age concept [J]. Buldng and Envronment, 2003, 38 (3): [4] LU Yajun, MA Zulang, ZOU Pnghua. Heatng, and ar condtonng [M]. Bejng: Chna archtecture and ndustry press, 2002 (n Chnese). [5] WU Wenzhong, YOU Shjun. Optmzng ar dstrbuton to mprove effectveness at subway staton platform [J]. Journal of Tanjn Unversty, 2008, 41 (11): (n Chnese). [6] Wu wenzhong, You shjun. Wave Moton of Smoke n Subway Fre Envronment [J]. Transactons of Tanjn Unversty, 2009, 15 (3): [7] WU Wenzhong, YOU Shjun. Analyss of smoke control zonng for an underground ralway platform [J]. Journal of HV&AC, 2009, 39 (1): (n Chnese). [8] WU Wenzhong. Study on ar age and smoke-control of fre at subway central-platform [D]. Tanjn: Tanjn Unversty, 2009 (n Chnese). [9] Tanjn subway company. Study on energy savng technology to envronmental control system of Tanjn subway [R] (n Chnese). [10] The thrd ralway survey and desgn nsttute of Chna. Feasblty study of Tanjn subway lne 1 [R] (n Chnese). [11] Shangha road and ral tunnel desgn nsttute. Envronmental control system outlne desgn of Tanjn subway lne 1 [R] (n Chnese).

5 Sustanable Ctes Development and Envronment Protecton IV / Ar Age Equaton Parameterzed by Ventlaton Grouped Tme / DOI References [3] Xantng L, Dongnng L, Xudong Yang, et al. Total ar age: an extenson of the ar age concept [J]. Buldng and Envronment, 2003, 38 (3): /S (03) [6] Wu wenzhong, You shjun. Wave Moton of Smoke n Subway Fre Envronment [J]. Transactons of Tanjn Unversty, 2009, 15 (3): /s z