ASHRAE Distinguished Lecturer Talk. Chandra Sekhar PhD, Fellow ASHRAE, Fellow ISIAQ. Learning Objectives

Transcription

1 ASHRAE Distinguished Lecturer Talk ASHRAE India Chapter, New Delhi EDUSAT HALL, G.B.Pant Polytechnic February 21, 2013 Chandra Sekhar PhD, Fellow ASHRAE, Fellow ISIAQ Department of Building, School of Design and Environment Learning Objectives 1. Describe an integrated IAQ-Energy audit methodology 2. Interpret the IAQ and Energy audit data from case studies in a hot and humid climate 3. Describe two Decoupled Ventilation systems - Single Coil Twin Fan & Personalised Ventilation 4. Quantify the enhanced IAQ and Energy performance of these two decoupled ventilation systems Event, Delhi, 21 Feb

2 Integrated IAQ-Energy Audit Methodology OBJECTIVES OF AUDIT Establish status of Indoor Air Quality (IAQ) Identify strategies for improving IAQ Basis for developing an IAQ audit and management program Event, Delhi, 21 Feb

3 Study Questi ionnaire nts ms Percentage of occupan experiencing symptom Figure 11 : A comparison of MALE and FEMALE Building Related Symptoms (Mean of all five buildings) - Here and Now (% ) Total Female Male Dryeye Blocknose Drythroat Dryskin Headache Lethargy Wateryeye Runnose Chesttight Flusymp Rash Other Total Female Male Building Related Symptoms Sekhar SC, KW Tham and KWD Cheong, Indoor Air Quality And Energy Performance of Air-conditioned Office Buildings In Singapore, Indoor Air International Journal of Indoor Air Quality and Climate, 2003, Volume 13, Issue 4, pp % 40.0% 35.0% Acceptability of Indoor Air Quality (% Dissatisfied) - A Comparison of Singapore and EU studies % Dissatisfies 30.0% 25.0% 20.0% 15.0% 10.0% 5.0% 0.0% Germany Singapore Switzerland Finland France United Kingdom Countries The Netherlands Greece Denmark Norway Event, Delhi, 21 Feb

4 Objectiv ve Measu rements IAQ parame eters DIMENSIONS OF INDOOR AIR QUALITY Chemical Biological Physical Continuous Monitoring Chemical Contaminant Profiles (5-7 days) Ventilation Characteristics (Air Exchange Rates) (1 evening) Particulate Profiles (2 days per location) Event, Delhi, 21 Feb

5 Spot Measurements Total Bacteria, Yeasts & Molds Temperature, Relative Humidity, Air Movement PM10 Particulate levels Total time taken :30 minutes per location rements ameters ve Measu ation para Objectiv Ventila VENTILATION STUDIES IN NINE AIR-CONDITIONED OFFICE BUILDINGS IN SINGAPORE Period of Study : A/P Chandra Sekhar, National University of Singapore Event, Delhi, 21 Feb

6 Factors affecting ventilation performance - space layout - fresh air quantity - supply diffusers and return grilles Indoor air flow pattern - Short circuiting - Piston flow - Perfect mixing Flow pattern affects Indoor Air Quality (IAQ) Building energy consumption A/P Chandra Sekhar, National University of Singapore VENTILATION CHARACTERISTICS THE VENTILATION MODEL Age-of-air average amount of time elapsed since molecules in a sample entered the building measured by tracer gas techniques "youngest" air found where the outdoor air comes into the room "oldest" air found at any other point in the room A/P Chandra Sekhar, National University of Singapore Event, Delhi, 21 Feb

7 TRACER GAS MEASUREMENTS AGE OF AIR VALUES LOCAL MEAN AGE OF AIR ROOM AVERAGE AGE OF AIR AIR CHANGE RATE Air Exchange Effectiveness (also known as Ventilation Effectiveness) type of tracers used usually colourless, odourless, inert gases (e.g. SF6) Important aspect of TG measurements - can be made in occupied buildings Concentration-decay method Air Change per Hour (ACH) slope of the tracer gas concentration decay curve Linear Plot Semi Log Plot C 0, t 0 ) Gas (ppm) Tracer Tracer Gas (ppm) ACH = ln(c 0 ln(c 1 ) t C 1, t 1 ) Time A/P Chandra Sekhar, National University of Singapore Time Event, Delhi, 21 Feb

8 Air Exchange Effectiveness Perfectly mixed air - datum for all three AEE parameters AEE = 1 AEE G = 2.0 "perfect" displacement flow AEE G < 1.0 shortcircuiting AEE G > 1.0 displacement flow the greater the deviations from unity, more pronounced are the two flow patterns A/P Chandra Sekhar, National University of Singapore Figure 1 : Summary of Air Change per Hour (ACH) values Building CC D A ACH Event, Delhi, 21 Feb

9 EE Figure 5 : Comparison of Localised Air Exchange Effectiveness (AEEL) Values Bu ild in g CC E C A AEEL A/P Chandra Sekhar, National University of Singapore r change rates (h -1 ) Zuraimi MS, Roulet C-A, Tham KW, Sekhar SC, David Cheong KW, Wong NH & Lee HK, A comparative study of VOCs in Singapore and European Office Buildings, Building and Environment, Volume 41, Issue 3, March 2006, Pages Nordic Climate Continental Europe Oceanic Europe Mediterranean Europe Tropical Climate Ai 0 DENMARK NORWAY FINLAND FRANCE GERMAN SWISS UK GREECE SPORE Air change rates (ACH) measured in the European and Singapore buildings studied Event, Delhi, 21 Feb

10 Energy Measurements A/P Chandra Sekhar, National University of Singapore Summary of measured and computed parameters Thermal Comfort, IAQ, Ventilation and Energy Event, Delhi, 21 Feb

11 Causes Pollutants Recommendations AHU-installed Bacteria Killers Occupant Density Fresh Air Provision Filtration (F/A Intake; AHU) Total Bacteria Total Y&M Particulate TVOCs/ Formaldehyde Fresh air filter into AHU Downwash zone + Door mats at entrance Better filtration Renovation - Close library Purging Replace carpets Carpets Equipment (Photocopiers; Computer Computer Clusters) Clusters) Carbon Dioxide Photocopiers (separate exhaust) Computer clusters Demand Control Ventilation Energy Efficient Healthy Buildings Single Coil Twin Fan System Personalised Ventilation System Event, Delhi, 21 Feb

12 2000 To date Single Coil Twin Fan (SCTF) Air-conditioning & Air distribution system Sekhar, S.C., Uma Maheswaran, C.R., Tham, K.W, and Cheong K.W, Development of energy efficient single coil twin fan air-conditioning system with zonal ventilation control, ASHRAE Transactions, 2004, Vol. 110, Pt 2, pp (Paper presented in Nashville, June 2004). Cheyyar, R U M, S C Sekhar, K W Tham and K W Cheong, "Single coil twin fan air-conditioning and air distribution system - Towards the development of a mathematical model of the compartmented coil". HVAC&R RESEARCH - International Journal of Heating, Ventilating, Air-conditioning and Refrigerating Research, 12, no. 3c, pp (Special Issue) (October 2006). SCTF Air-conditioning and Air Distribution System (US and PCO Patents) F.A Filter F/A Comp Coil F/A VAV Fan F/A P To other VAV Boxes In Other Zones R/A CHWR CHWS R/A Filter R/A Comp Coil By-pass Damper Modulating Valve R/A VAV Fan CO 2 R/A P F/A VAV Box R/A VAV Box T Mixing Box S/A Typical Zone VAV Box Event, Delhi, 21 Feb

13 SCTF Prototype Findings Comparison of Energy Consumption Cooling Capacity (kw W) Conventional Type of System SCTF Outside Air O/A : ON Coil VAV System 1 : Coil Condition Curve O/A : OFF Coil Space Condition 10-15% energy savings Return Air R/A : ON Coil VAV System 2 : Coil Condition Curve R/A : OFF Coil SCTF system for independent conditioning of fresh air and return air streams A Psychrometric Performance Event, Delhi, 21 Feb

14 The Enterprise Challenge (TEC) Grant Field Trial A Test-Bedding Project Bldg TOP = June 2005 SCTF Installed = June 2005 Air-conditioned = 2,750m 2 Floor Area for SCTF system DESIGN DATA F/A = 5,400 cmh R/A = 60,000 cmh Coil Cap = 86 kw (F/A) 233 kw (R/A) Field Trial A Test-Bedding Project Conference Room Meeting Room 4 Open Plan Space 3 F/A 2 1 R/A Core SCTF AHU Return-duct mounted T&CO 2 sensors Individual Offices Staircase 5 The Enterprise Challenge (TEC) Grant Event, Delhi, 21 Feb

15 roject Field Trial A Test-Bedding Pr 9 ppm Event, Delhi, 21 Feb

16 Temperature (Level 3) Field Trial A Test-Bedding Project r temperature : C ge = 23 C Indoor range Averag Indoor relative hum midity range : %RH Average = 50 %RH T(C) %) RH(% /26/ /26/ /27/ /28/ /28/ /29/0 06 Time 06/30/ /30/0 06 Relative Humidity (Level 3) /26/06 06/26/06 06/27/06 06/27/06 06/28/06 06/28/06 06/29/06 06/30/06 06/30/ Time point 1 point 2 point 3 point 4 point 5 point 1 point 2 point 3 point 4 point 5 Energy consumption (W/m2) Energy consumption (w/m2) Energy consum mption(w/m2) 0 3/19/ :5 50:00 PM 3/19/ :5 50:00 PM 3/19/2007 2:5 50:00 PM 3/19/2007 4:5 50:00 PM 3/19/2007 6:5 50:00 PM 3/19/2007 8:5 50:00 PM 3/19/ :5 3/20/ :5 3/20/2007 2:5 3/20/2007 4:5 3/20/2007 6:5 3/20/2007 8:5 3/20/ :5 50:00 PM 3/20/ :5 50:00 PM 3/20/2007 2:5 50:00 PM 3/20/2007 4:5 50:00 PM 3/20/2007 6:5 3/20/2007 8:5 50:00 PM 3/20/ :5 50:00 PM Time 3/21/ :5 3/21/2007 2:5 3/21/2007 4:5 3/21/2007 6:5 3/21/2007 8:5 3/21/ :5 50:00 PM 3/21/ :5 50:00 PM 3/21/2007 2:5 50:00 PM 3/21/2007 4:5 50:00 PM 3/21/2007 6:5 50:00 PM 3/21/2007 8:5 50:00 PM 3/21/ :5 3/22/ :5 3/22/2007 2:5 3/22/2007 4:5 3/22/2007 6:5 3/22/2007 8:5 3/22/ :5 Normalised Energy Consumption in terms of coil capacity (W/m 2 ) Compartmented Cooling Coil SCTF system (Level 3) Event, Delhi, 21 Feb

17 Zero Energy BCA Academy SCTF Compartmented Coil FCU F/A Filter F/A Comp Coil F/A Fan speed F/A R/A CO 2 RA CO 2 R/A Comp Coil Tmix 1+2 To S/A Diffusers T TRA R/A Filter R/A Fan speed TZ1 - Zone Set-point Temperature (TRA, which will track TZ1 is used to control the speed of the R/A fan) CHWR CHWS Modulating Valve CO 2 Z1 - Zone Set-point CO2 level (CO 2 RA which will track CO 2 Z1 is used to control the speed of the F/A fan) Zero Energy Building Project : FCU 1 3 & 1 4 Event, Delhi, 21 Feb

18 SCTF vs Conventional VAV System AHU 2 1 AHU 3 1 AHU 3 2 AHU 3 3 Design Recirculated Airflow [m 3 /h] Design Fresh Airflow (F/A) [m 3 /h] SCTF System F/A (Ventilation Efficiency=1) [m 3 /h] Conv VAV System F/A (Ventilation Efficiency=0.8) [m 3 /h] SCTF System % F/A [%] Conv VAV System % F/A [%] IMPROVED FRESH AIR CONTROL = LESS ENERGY!!! AHU 2-1 AHU 3-1 AHU 3-2 AHU Baseline cooling Actual cooling Percent difference * [kw] [kw] [%] * SAVINGS FOR APRIL Event, Delhi, 21 Feb

19 2002 To Date Personalised Ventilation (PV) system Personalised Ventilation (PV) System Deliver fresh air directly to the Occupant breathing zone Potential to enhance Acceptability of ventilation Indoor Air Quality Thermal comfort Event, Delhi, 21 Feb

20 Desk-mounted PV System integrated t with Ceiling Supply MV System Sekhar, S C, N Gong, K W Tham, K W Cheong, A.K. Melikov, D.P. DP Wyon and P.O. Fanger, "Findings of personalised ventilation studies in a hot and humid climate". International Journal of Heating, Ventilating, Air-conditioning and Refrigerating Research (HVAC&R Research), Vol 11, no. 4 Gong, N, K W Tham, AK Melikov, DP Wyon, S C Sekhar and K W Cheong, "The acceptable air velocity range for local air movement in the Tropics". HVAC&R Research, International Journal of Heating, Ventilating and Air-Conditioning Engineers (ASHRAE), Vol 12, No. 4, pp , (October 2006). (United States). Experimental Protocol Ambient and PV air temperatures Thermal comfort parameters within the occupied zone Breathing temperature in the occupant breathing zone Concentration levels of various indoor pollutants SF 6 tracer gas measurements - ventilation effectiveness Questionnaire responses 52 Event, Delhi, 21 Feb

21 Ventilat ion Effectiven ness Higher the Better Saves ENERGY PV Without PV Experimental conditions Thermal comf fort acceptability Very Acceptable With PV W/O PV Very Unacceptable Subjects Mean responses of Thermal Comfort acceptability Event, Delhi, 21 Feb

22 IAQ accepta ability Very Acceptable with PV without PV Very Unacceptable Subjects Mean responses of IAQ acceptability PV system Consistent trends of thermal comfort & IAQ ratings Observed INCREASE with INCREASING PV flow rate And DECREASING with INCREASING PV temps at Ambient temp of 26 C 59 Event, Delhi, 21 Feb

23 Energy savings occur due to A warmer space temperature, such as 26 C, accompanied by a PV air temperature of 23 C, implies that the space cooling load is reduced in comparison with a conventional air-conditioning system in which the space is typically maintained at 23 C. An absolute reduction in the total fresh air quantity provided is possible, as it is now directly supplied as inhaled air to the occupant breathing zone. Personalised Ventilation Systems Practical Applications Challenges Aesthetics Possibilities Event, Delhi, 21 Feb

24 Ceiling-Mounted PV System integrated with Ceiling Supply MV System Ceiling mounted PV System integrated with ambient MV system Yang, B and S C Sekhar, "Three dimensional numerical simulations of a hybrid fresh air and recirculated air diffuser for decoupled ventilation strategy". Building and Environment, (2007), Vol.42, Issue 5, pp (United Kingdom). YANG, B, Arsen Melikov and S C Sekhar, "Performance evaluation of ceiling mounted personalized ventilation system". ASHRAE Transactions 2009, Vol. 115, Part 2, pp (United States). Yang, B, S.C.Sekhar and Arsen Melikov, Ceiling mounted personalized ventilation system integrated with a secondary air distribution system A human response study in hot and humid climate. Indoor Air International Journal of Indoor Environment and Health (2010). Volume 20, no. 4 (2010): (Denmark). YANG, B, S C Sekhar and Melikov Arsen, "Ceiling mounted personalized ventilation system in hot and humid climate An energy analysis". Energy and Buildings, (2010). (Switzerland). Event, Delhi, 21 Feb

25 CFD simulation more fresh air is supplied directly into the breathing zone without mixing with recirculated air and much better IAQ in the occupied zone can be realized. D V o X nl X nl Centre-line Veloc city X, V X nl No Blockage Or thermal plume Blockage (unheated manikin) Blockage & Thermal Plume (heated manikin) X nl : Neutral Level under various scenarios Event, Delhi, 21 Feb

26 4 L/s 8 L/s 12 L/s 16 L/s dimension nless neutral leve el-x nl/d A B C D personalized airflow rate (L/s) Dimensionless neutral level as a function of personalized airflow rates A B C D Heated Manikin Ceiling-mounted PV system in conjunction with ceiling supply mixing ventilation system 23.5/ / /21 Χ 26/23.5 * 26/26 lity Inhaled air qual PV airflow rate (L/s) Y-axis -1 = very unacceptab ble, 0 = just unacceptab ble/acceptable, +1 = very acceptable e Event, Delhi, 21 Feb

27 Desk-mounted PV System Integrated with UFAD System Li, Ruixin, S.C.Sekhar and A.K.Melikov, Thermal Comfort and Indoor Air Quality in rooms with Integrated Personalized Ventilation and Under-Floor Air Distribution Systems. HVAC&R Research, Volume 17, Number 5, pp ,ASHRAE. Li Ruixin, S.C.Sekhar and Arsen Melikov, Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate. Building and Environment journal, Vol 45 (2010): (United Kingdom). Field Environmental Chamber (FEC) experimental setup - Desk mounted PV with UFAD system Event, Delhi, 21 Feb

28 Methods- Experimental Conditions Table 1 Experimental Conditions System Type Exp. Condition (Session no.) Temperature ( C)/ ( F) T room T UFAD supply T PV supply PV flow rate (L/s)/(CFM) Total volume ventilation system (UFAD) flow rate (L/s)/(CFM) UFAD+PV / / /78.8 5/ /1017 UFAD+PV / / / / /1017 UFAD+PV / / /71.6 5/ /1017 UFAD+PV / / / / /1017 UFAD+PV / / /78.8 5/ /763 UFAD+PV / / / / /763 UFAD+PV / / /71.6 5/ /763 UFAD+PV / / / / /763 IAQ 10 November10-12, 2010 Cold Feet Thermal sensation at feet and acceptability of air movement at feet (Thermal sensation scale: = 3 cold, = 2 cool, = 1 slightly cool, =0 neutral, =+1 slightly warm, =+2 warm, =+3 hot; Air movement acceptability: 0 ~50 = very unacceptable ~ just unacceptable, 50~100 = just acceptable ~ very acceptable) Event, Delhi, 21 Feb

29 Facial Thermal Sensation Cooler (better) thermal sensation at face Whole Body Thermal Sensation Cooler (better) thermal sensation whole body freshness Perceived inhaled air f y = x R² = inhaled air freshness inhaled air temperature y = x R² = Pe erceived inhaled air te emperature Acceptability of perceived air quality Event, Delhi, 21 Feb

30 Human Response Studies - Key Observations The use of PV-UFAD improved subjects thermal sensation in comparison with UFAD alone or mixing ventilation. The cold feet complaint decreased when the temperature of the air supplied from the UFAD was increased. The use of the PV provided the subjects with the preferred slightly cool thermal sensation at the head and face. Local cooling of the head and face could be achieved by decrease of the temperature of the personalized air or increase of its flow rate, i.e. increase of the air velocity at the head and face region. Tracer gas measurements Two indices, as defined below were calculated to evaluate the performance of the integrated PV and UFAD systems: personal exposure effectiveness (PEE) and Personal exposure index (PEI). Event, Delhi, 21 Feb

31 Methods The PEE index expresses the percentage of personalized air in inhaled air. It is derived from the following equation PEE = (C R,SF6 C I,SF6 )/(C R,SF6 C PV,SF6 ) C- R, SF6 = SF- 6 concentration of the tracer gas in the exhaust/return air (ppm), C PV, SF6 = SF 6 concentration of the tracer gas in personalized air (ppm), = SF 6 concentration of the tracer gas in the inhaled air (ppm). C I, SF6 The local ventilation effectiveness for the removal of pollutants, ε V V,, also called the PEI, is expressed PEI = (C R C )/(C I C ) C R = contaminant concentration in the exhaust/return air (ppm), C I = contaminant concentration in the inhaled air of a person (ppm) C = contaminant concentration in the outdoor supply air (ppm). UFAD integrated with PV System PEI PV L/s 0.0 PV S/A UFAD S/A PEI PEE PEE PEE and PEI values Cermak, R., 2004, Design strategies for personalized ventilation. PhD Thesis (ISBN ), International Centre for Indoor Environment and Energy, Department of Energy Engineering, Technical University of Denmark. Chapter 5, Cermak, R., Melikov, A.K., Forejt, L. and Kovar, O., 2006, Performance of personalized ventilation in conjunction with mixing and displacement ventilation, International Journal of heating, Ventilation and Refrigeration Research. Vol.12, no.2, pp Event, Delhi, 21 Feb

32 Tracer Gas Studies - Key Observations S/A temp of PV air has stronger effect on the PEE and PEI than PV air flow rate. The cooler PV air results in higher PEE and PEI. UFAD supply conditions have a marginal effect on the PEE and PEI, but not comparable to that of PV. The cooler UFAD supply air temp tends to result in lower PEE and PEI. Final Words Integrated IAQ Energy Audit IAQ parameters, Ventilation parameters, Human Response, Energy performance Case Studies Energy Efficient Healthy Buildings Single Coil Twin Fan System Energy Efficient Healthy Buildings Personalised Ventilation System Event, Delhi, 21 Feb

33 Event, Delhi, 21 Feb