Ch. 12 Human Thermal Comfort and Indoor Air Quality

Transcription

1 Ch. 12 Human Thermal Comfort and Indoor Air Quality

2 Introduction - Temperature & Humidity Control - IAQ Indoor Air Quality : control of indoor airborne contaminants 12.2 Energy balance on the human body - Steady-state energy balance - Model by Fanger

3 -3- Q Q Q M skin respiration Q C QR QE QC QE M : metabolism C : convection R : radiation E : evaporation skin respiration

4 -4- - for an unclothed body in the absence of solar radiation v Q h A t t h A t t h A W W h M c sk sk R R sk r E w s, sk fg, sk m c t t m W W h res pa ex res ex fg, b exhaled res sk - Clothing : Q remained unchanged respiration Q is modified by clothing skin

5 -5- Q Q Q sen C R h t t h t t A c cl R cl r cl ( h h ) t h t h t A c R cl c R r cl h h h C R h t h t Q h t A h c R r sen cl cl t 0 h t c h t h R r Q h t t A sen cl 0 cl

6 -6- operative temperature, t o hct = h t h R r in some case t Q h t t A sen cl o cl ( tsk tcl ) Q ht t A R / A o t tr h h h 2 2 o c R sen cl o cl cl sk R cl tcl tsk Qsen A sk R ht Q t A Q cl sk sen o cl sen Ask R t Q t cl sk sen o Ask Q A sen h cl t

7 -7- A Q A t t Q R Q Q sk sen sk sk o sen cl Acl h sen lat sk sk o cl w s, sk fg, sk v cl v E cl, w sk sk o w s, sk fg, sk M res pa ex fg, b ex Ask v A w Rcl Rcl v hacl he Acl, w '' M A t t Ask Rcl ha A W W h R A t t A W W h Q m c t t h W W q In a similar manner A Q A sk M sk 1.8m Aw ha Table

8 -8- Table 12.1 Typical Metabolic Heat Generation for Various Activities

9 -9- - normlized metabolic rate : met 1 met 58.2W 2 m t 33.7, t 36.8 sk W h s, sk fg, sk b kg w kg kj kg a w hr 4.7W 2 m hc (seated) 3.1W 2 m 0 V 0.2 m s V W 2 m 0.2 V 4.0 m s hc (active) 5.7 M 0.85 W 2 m 1.1 M 3.0

10 -10- v h h / Le c E c pa Le Aw w ( ) A sk normal skin moisture loss comfortable

11 Clothing: Effect on thermal resistance, moisture resistance, wet and dry surface areas R cl I I cl T Unit: clo v R 0.9 R / i cl cl cl v R 0.9 R / i T cl T m res KM :( for clothing only) :(between skin and environment) 0.155m 2 W 4 kg K a s met tex t 32W 5 Wex t 0.2W

12 -12- Table 12.2 Typical Insulation and Permeability Values for Clothing Ensembles

13 Environmental parameters - Fanger 1. Air dry-bulb temp 2. Air velocity 3. Air humidity 4. Mean radiant temp 5. Activity level 6. Clothing

14 Environmental Comfort Indices Trade off beween temperature and humidity Assumptions Q skin r A A const. w Q t t t 0 cl, w res at low metabolic rate A t t A W W h Q m c t t h sk sk o w s, sk fg, sk M res pa ex f Ask v A g, b w Rcl Rcl v hacl he Acl, w, Q C t t C W W sk sen sk o lat s sk W ex W 임의의온도 (t ), RH=50%( W W / 2) 인점의 Heat Loss 0 W Qsk Csen tsk to Clat Ws, sk 2 st, st, o o

15 -15- Effective temperature(et*) : all other values of t o and W that provide the same heat loss Q ሶ Q sk = C sen t sk t 0 +C lat W s,sk W If Qሶ sk = const., Q C t t C W W sk sen sk o lat s sk d(c sen t sk t 0 +C lat W s,sk W )=0 dw dt o C C sen lat (for Q const) sk

16 -16- H.S.I Heat Stress Index : Belding and Hatch Criteria 1) t <35 sk 2) sweat rate < 1[ l ] hour Q H. S. I. 100 E,max 0.5 E M V ( 35) 0.012( r - 35) E,max E Q Q Q t t Q V ( W) W.C.I Q A h t t sen sk sk o h t0 (for Qsen const)

17 -17- Table 12.4 Equivalent Wind-Chill Temperatures of Cold Environments

18 Body Regulatory Processes Against Heat or Cold

19 Prediction of Human Thermal Comfort

20 Predicted Mean Vote(PMV) +3 hot +2 warm +1 slightly warm 0 neutral -1 slightly cool -2 cool -3 cold PMV= a * t b* P c * W Pv ( P P ) v v

21 Predicted Percentage of Dissatisfied(PPD) & PMV (Fanger)

22 Airborne Contaminants dry air : N 2, O 2, Ar, CO 2... water vapor : H O Contaminants 2 Dusts,fumes,smokes Nonviable Mists and fogs - Particles Aleergens,molds,bacteria Viable Disease transmitting Inorganic - Gases and vapors Organic * normal boiling point molecular weight polarity

23 -23-

24 Acceptable indoor levels of airborne contaminants Recommended outdoor-air level - U.S. National Ambient Air Quality Primary Standard : annual mean values Workplace (American Conference of Govermental Industrial Hygienists) - Threshold Limit Values (TLVs) : Preventing harmful effects to worker who may be exposed for 8 to 10 hours a day Time Weighted Average values (TWA) Short Term Exposure Limit values (STEL) - Mixture whose constituents have similar toxicological effects: C TLV C TLV

25 -25- Indoor concentration limits for nonindustrial buildings : - fewer standards & guidelines - outdoor limits 에기준 - work place 의 TLV 의 ASHRAE ppm, ppb - ppm: number of gas molecules per million molecules of air ppm MP mg 3 = m t P=mmHg, total pressure

26 -26- Particles 3 long-term ambient air concentration :75μg m 3 short-term limit : 260μg m for 24 hours - ACGIH : 10mg m 3 - Toxic chemical : 별도규정 - Particle size : 중요 large size : upper repiratory tract smaller size : gas-exchange region

27 Control of indoor airborne contaminants 1 Source control 2 Removal control 3 Dilution control Source control - best method - ban smoking from indoor areas - carpeting and composite wood-based products that release a minimal amount of harmful gases - good choice of paints, cleaning agents - local exhaust : laboratory fume hoods

28 -28-

29 -29- Removal control - Gas removal : adsorbent, chemisorber Adsorption Desorption - activated alumina : m g - activated carbon : m g

30 breakthrough time : 급격히증가하는시간

31 -31- media filters - Particle removal electrostatic air cleaners natural settling Media filters - most common - protect the HVAC equipment - large particle 에대해 effective - small particle 에대해서는 not very effective

32 -32- Particulate air cleaner p, performance 1 2 p : fan power 2 mass ratio collection efficiency number of particles collection

33 -33- interception Collection Mechanism impaction diffusion most penetrating particle size : 0.1~0.5μm

34 -34- dust cake most ventilation applications:replaced(monitoring P) shaking industrial application : cleaned by reversing the flow replaceable panel filter bag filter renewable media filter:rotating

35 -35- Electrostatic precipitators - All air cleaners : possibility of fungal of bacterial growth

36 -36- Dilution Control Using Ventillation - air exchange(or change) rate; V I Vol 환기횟수 Nominal air exchange rate; Space air exchange rate; I s I n Voa Vol V sa Vol

37 -37- Dilution Control Using Ventillation - age-distribution idea (Sandberg) - p : age - residual life time : - residence time : p r r

38 -38- nominal time constant : Vol n V oa space time constant : Vol s V sa local ventilation efficiency at point p: C -C p d n in p, p 0 p Cin -Co Average ventilation efficiency: ave n 2 p perfectly mixed room : piston flow : ave 1 s n ave 0.5 undirectional-flow clean room : a room with short circuiting : ave ave ave 0.5 p

39 -39-

40 -40-

41 Modeling of indoor contaminant concentration Simple model Steady model Steady state uniform concentration

42 -42- Case 1 : 100% outdoor P R G P o Pe Po G R V V V C o o o s C o o e G R V a. G 0, R 0 Cs C b. R G Cs Co c. Vo Cs Co o

43 -43- Case 2 : recirculation C V C V R G V V C C o o s r o r s ac m ac o r m o o s r o Vo Vrac Cs CoVo 1 ac G r o o s r o o s r ac o o s r o r s s R V V C C V V C V C V V R C V C V C V C V C V G V V C C C V 1 o o ac V V o r ac G