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Review of Parametric Studies for Optimizing Laboratory Ventilation
HE Yueyang (Dr.), Department of Building, [email protected]
Daniel HII Jun Chung (Dr.), School of Design & Environment, [email protected]
WONG Nyuk Hien (Prof.), Department of Building, [email protected]
PECK Thian Guan (Dr.), Office of Safety Health and Environment, [email protected]
22 October 2019
mailto:[email protected]:[email protected]:[email protected]:[email protected]
2
◼ Introduce the background of our lab ventilation research project in NUS
◼ Review existing standards/parametric studies of air flow rates
◼ Review existing standards/parametric studies of air distributions
◼ Discuss lab design parameters to be tested in CFD simulations
◼ Objectives
Section 1
Background: Lab Energy Performance
0
100
200
300
400
500A
vera
ge E
ner
gy U
se In
ten
sity
(kW
h/m
2yr
)2013 2016 2017
◼ University energy consumptions in Singapore
4Source: Building Construction Authority (BCA), 2018
◼ BCA Green Mark for laboratories (GM Lab: 2017)
5
◼ Background• Official launch: 13 June 2017
• World’s 1st green certification scheme for laboratories design and
operation
◼ Lab 2-1 Energy efficiency• Use more efficient air distribution system (baseline: 0.35 kW/ton)
• Design for air recirculation within laboratory while meeting safety
requirement
• Adopt VAV lab air flow and variable flow exhaust controls
◼ Lab 2-2 energy effectiveness• Use occupancy sensor or sash position monitoring for fume hood/
biosafety cabinet to reduce exhaust air ventilation
• Use VAV fume hood/ biosafety cabinet with lower face velocity (Platinum:
≤ 0.5 m/s & Gold: ≤ 0.6 m/s for biological and chemical lab)
• Link sash position/exhaust rate/face velocity monitoring to BMS
Source: Building Construction Authority (BCA), 2017
◼ Inaugural Platinum awards
6
◼ Lab ACH Control Band:
• Cornell’s Laboratory Ventilation Management Program: never go down to 2ACH, 3ACH is bare
minimum (Source: https://sp.ehs.cornell.edu)
• OSHA’s Lab Standard: 4-12 ACH: adequate general ventilation
◼ Inaugural Platinum awards
• NUS Chemistry Lab – Tahir Foundation
• Cambridge Centre for Advanced Research and Education (Cares)
• Agency for Science, Technology and Research's (A*Star) Institute of Bioengineering and
Nanotechnology - IBN Chemistry Lab
7
Tahir Foundation Building (MD1)
Floor plan at level 17
Single laboratoryequipped with 8 fume hoods
(Area = 48.2 m2/ 518.8 ft2)
Source: NUS
◼ Compact laboratory design in NUS
◼ Diagram for optimizing lab ventilation
8
Air Flow Rates (ACH) Air Distributions
CFD Parametric Studies
Review of Existing Standards and Researches
Chemical Spill Experiments
Potential ACH ReductionSafety Requirements
Validation
Evaluation
Future Lab Designs
Section 2
Review: Air Flow Rates
◼ Reviewed lab ventilation standards and criteria
10
NO Standard Region
1 OSHA Federal register 29 CFR part 1910 US
2 ANSI/ASHRAE Standard 62.1-2016 Ventilation for acceptable indoor air quality US
3 NFPA 45-2015 Standard on fire protection for laboratories using chemicals US
4 ANSI/AIHA/ASSE Z9.5-2012 Laboratory ventilation US
5 ASHRAE Handbook 2015 - HVAC Applications, Chapter 16: Laboratories US
6 ACGIH 2016 Industrial ventilation: a manual of recommended practice for design US
7 ANSI/ASHRAE Standard 110-2016 Method of testing performance of laboratory fume hoods US
8 SEFA 1-2010 Laboratory fume hoods recommended practices US
9 Cornell University’s laboratory ventilation management program (LVMP) US
10 International Building Code 2012 ICC
11 BS 7258-1994 Laboratory fume cupboards / BS EN 14175 -7 fume cupboards British
12 DD 191-1990 Method for determination of the containment value of a laboratory fume cupboard British
13 DIN 1946-7 Ventilation and air conditioning Germany
14 VDI 2051 Air-conditioning - Laboratories Germany
15 SS 553-2016 Code of practice for air-conditioning and mechanical ventilation in buildings Singapore
16 SS 554-2016 Code of practice for indoor air quality for air-conditioned buildings Singapore
17 SS 641-2019 Code of practice for fire safety for laboratories Singapore
18 GM Lab: 2017 BCA Green Mark for laboratories Singapore
19 SCDF Fire Code 2018 chapter 7 Air-conditioning and mechanical ventilation systems Singapore
20 WSH guidelines – Laboratories handling chemicals 2014 Singapore
21 WSH guidelines – Management of indoor air quality in air-conditioned workplaces 2016 Singapore
22 Workplace safety and health act Singapore
◼ Standards for fume hood
11
Document Standard Year
Laboratory fume cupboards BS 7258-2 1994 U ≥ 0.3 m/s 1994
SEFA1-2010 U = 0.3 – 0.5 m/s 2010
ANSI/AIHA Z9.5
U = 0.3 – 0.4 m/s (excellent containment characteristics)U = 0.4 – 0.5 m/s (most hoods)
U = 0.5 – 0.6 m/s (most hoods with higher operating costs)U = 0.6 – 0.7 m/s (performance is not significantly better)
2012
BCA Green Mark for laboratories GM Lab: 2017
U ≤ 0.5 m/s (Platinum)U ≤ 0.6 m/s (Gold)
2017
◼ Standards for air flow rates (ACH)
12
Document Standard Highlight Year
OSHA 29 CFR, Part 1910 ACH = 4 – 12 1990
NFPA 45-2004ACH ≥ 4 (unoccupied)
ACH > 8 (occupied)2004
NFPA 45-2015 N/A 2015
ANSI/AIHA Z9.5 ACH = 4 – 10⚫ ACH cannot meet all conditions. Furthermore, ACH is not the
appropriate concept for designing contaminant control systems.2012
ASHRAE 62.1-2016 ACH ≥ 1.2 (9-foot ceiling) 2016
ASHRAE handbook HVAC
2007ACH = 6 – 10 (occupied) 2007
ASHRAE handbook HVAC
2015N/A
⚫Minimum ventilation rates should be established on a room-by-room basis …
2015
ACGIH 2016 N/A⚫ ‘ACH’ is a poor basis for ventilation criteria where environmental
control of hazards, heat, and/or odors is required …2016
◼ Standards for air flow rates (ACH)
13
Document Standard Highlight Year
Cornell University LVMPACH = 4 – 8 (normal)
ACH = 3 – 6 (moderate)
⚫ Low ventilation: less than “moderate” rates, determined by review of operations in lab.
⚫ Lab-specific ventilation: determined by specific review of non-chemical hazards in lab.
2013
International Mechanical
Code (IMC) 2009ACH ≥ 1.2 (9-foot ceiling) 2009
DIN 1946-7:2009-7 ACH ≥ 9.1 (9-foot ceiling supply) 2009
VDI 2051 Air-conditioning
- LaboratoriesACH ≥ 9.1 (9-foot ceiling supply) 2018
Singapore Civil Defence
Force (SCDF) fire code
2018
ACH = 4 – 8 (Chemical/hazardous materials warehouses)
ACH ≥ 20 (rooms involving use of flammable and explosive substances)
2018
SS 641-2019 Code of
practice for fire safety for
laboratories using
chemicals
ACH = 8 – 12 (prescribed value)ACH = 4 – 8 (further reduction based
on risk assessment)
⚫ For energy conservation purposes, the air change rate for occupied laboratories can be reduced via the Risk Assessment Flow Chart
2019
◼ Parametric study of ACH
14
ACH (-) Floor area (m2)
Method References2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
55.0 CFD Liu et al., 2017
22.5 CFD Barbosa & Brum, 2017
21.0 CFD Morcos et al., 2014
70.0 Measurement Stuart et al., 2014
N/A Measurement Sweet & Stuart, 2013
21.0 Measurement Jin et al., 2012
65.0 Measurement Klein et al., 2010
65.0 Measurement Klein et al., 2009
73.0 Measurement Smith & Smith, 2009
N/A CFD Schuyler, 2009
60.0 CFD Memarzadeh, 2009
60.0 CFD Memarzadeh, 2007
N/A N/A Sandru & Ouyang, 2005
◼ Summary of ACH as a design parameter
15
◼ Existing standards prefer a case-by-case criteria to a common criteria of ACH
◼ Existing studies mainly focus on the ACH ranged from 6 to 12
◼ ACH is not a appropriate basis for ventilation criteria
◼ Minimum ventilation rates should be established on a room-by-room basis considering the hazard level
16
◼ SS 641-2019 Code of practice for fire safety for laboratories using chemicals
Section 3
Review: Air Distributions
◼ Standards for air flow distribution
18
Document Category Highlight Year
ANSI/AIHA Z9.5
Supply location,Exhaust location
⚫ Supply air diffusers close to the personnel corridor and entry door to the lab
and far from the major exhaust devices.
⚫ Hoods and exhaust devices away from entry doors and exit corridors2012
CFD solutions ⚫ Additional design information can be obtained using CFD
ASHRAE handbook
HVAC 2015
ACH,Supply-exhaust location,
supply type, pollutant source location, pollutant release rate, heat source
position, room layout
⚫ Airflow patterns, temperature, and particle distribution … depend on several
interrelated factors
⚫ The success of a mixed air distribution system depends primarily on supply
diffuser location.
2015
CFD solutions
⚫ Physical testing and measurements … are time consuming and labor
intensive, … analysis of various realistic scenarios through CFD simulations
becomes an attractive alternative.
◼ Standards for air flow distribution
19
Document Category Highlight Year
DIN 1946-7:2009-7 Supply-exhaust location
⚫ The flow of air within the lab is primarily determined by the position and construction of supply air openings.
⚫ Supply air openings shall be constructed and arranged in such a way that they will not interfere with the extract air equipment.
2009
VDI 2051 Air-
conditioning -
Laboratories
ACH, room space, room layout
⚫ Air flow patterns in lab areas depend on the intended use and the associated air volume flow rates and cooling loads. Further items to consider include the space required for the ventilation equipment and the arrangement of the components and devices.
2018
Workplace safety
and health
guidelines–
laboratories
handling chemicals
Pollutant-exhaust location,Local exhaust location
⚫ Air exhaust points should be located as near as possible to expected contaminant sources
⚫ Fume cupboards should be located away from doors and high traffic areas2014
◼ Parametric studies at lab scales
20
Authors Supply positionSupply
propertyExhaust/return
positionExhaust/ return
property Spill position
Chemical property
Methods
Liu et al., 2017
• Wall-mount supply 1• Wall-mount supply 2• Wall-mount supply 3• Ceiling supply 1• Ceiling supply 2• Ceiling supply 3• Ceiling supply 4
• 360 × 360 • 420 × 420
• Wall return 1• Wall return 2• Wall return 3• Wall return 4• Ceiling return 1• Ceiling return 2
• X 1
• Bench-top 1• Bench-top 2• Bench-top 3• Bench-top 4
• Benzene CFD
Jin et al., 2012 • Ceiling supply • Square• Bench exhaust• Wall exhaust 1• Wall exhaust 2
• X 1
• On the desk • On the floor near
an occupant • On the floor away
from occupants
• SF6 measurement
Klein et al., 2009
• Ceiling supply• 3 grilles • 6 grilles
• Overhead exhaust grill
• X 6• Floor level• Bench-top
• Diethylether
measurement
Klein et al., 2010
• Ceiling supply • 6 grilles• Overhead
exhaust grill• X 6
• Floor level• Bench-top
• Ether• Acetone• Ethanol
measurement
Memarzadeh, 2009
• Door gap and ceiling• Linear and
square
• Ceiling exhaust • Bench hood
exhaust
• X 1• X 2• X 4
• Bench-top N/A CFD
Morcos et al., 2014
• Ceiling supply • Square• Bench exhaust• Wall exhaust 1• Wall exhaust 2
• X 1
• On the desk • On the floor near
an occupant • On the floor away
from occupants
• SF6 CFD
◼ Summary of the design parameters affecting lab ventilation
21
◼ Existing standards provide some general recommendations for laboratory layouts
◼ Existing studies mainly focus on supply/exhaust/return/chemical emission positions and their properties
◼ CFD solution is recommended for additional design information
Section 4
Parametric Studies
23
ScenarioRoom exhaust
operationHood exhaust
operationPollutant position Measuring variable
1 OnOn
(100% open sash)N/A
Air/face velocity (U), air temperature (Tair) and surface temperature (Tsurface)
2 On Off Bench-top
VOC concentration (VOC)
3 On Off Ground
◼ Spill experiments for CFD validation
◼ Baseline laboratory configuration
ScenarioP1: Fume hood
operationP2: Supply response
P3: Fume hood position
P4: Supplyposition
P5: Room exhaustposition
Baseline Single Synchronous Aside Above-corridor Ceiling
Pollutant source
24
◼ Testing design parameters
BaselineP1: Fume hood operation
MultipleP2: Supply response
Asynchronous
P4: Supply positionAbove-bench
P5: Room exhaust position
FloorP3: Fume hood position
Central25
◼ Testing design parameters
BaselineSingle
P1: Fume hood operationMultiple
P2: Supply response
Asynchronous
P4: Supply positionAbove-bench
P3: Fume hood positionCentral
P5: Room exhaust position
Floor26
◼ Testing design parameters
BaselineSynchronous
P1: Fume hood operationMultiple
P2: Supply response
Asynchronous
P4: Supply positionAbove-bench
P3: Fume hood positionCentral
P5: Room exhaust position
Floor27
◼ Testing design parameters
BaselineAside
P1: Fume hood operationMultiple
P2: Supply response
Asynchronous
P4: Supply positionAbove-bench
P3: Fume hood positionCentral
P5: Room exhaust position
Floor28
BaselineAbove-corridor
P1: Fume hood operationMultiple
P2: Supply response
Asynchronous
P4: Supply positionAbove-bench
P5: Room exhaust position
FloorP3: Fume hood position
Central
◼ Testing design parameters
29
◼ Testing design parameters
BaselineCeiling
P1: Fume hood operationMultiple
P2: Supply response
Asynchronous
P4: Supply positionAbove-bench
P3: Fume hood positionCentral
P5: Room exhaust position
Floor (*dense gas)30
◼ Matrix of testing design parameters (pending)
ScenarioP1: Fume hood
operationP2: Supply response
P3: Fume hood position
P4: Supplyposition
P5: Room exhaustposition
1 Single Synchronous Aside Above-corridor Ceiling2 Single Synchronous Aside Above-corridor Floor3 Single Synchronous Aside Above-bench Ceiling4 Single Synchronous Aside Above-bench Floor5 Single Synchronous Central Above-corridor Ceiling6 Single Synchronous Central Above-corridor Floor7 Single Synchronous Central Above-bench Ceiling8 Single Synchronous Central Above-bench Floor9 Single Asynchronous Aside Above-corridor Ceiling
10 Single Asynchronous Aside Above-corridor Floor11 Single Asynchronous Aside Above-bench Ceiling12 Single Asynchronous Aside Above-bench Floor13 Single Asynchronous Central Above-corridor Ceiling14 Single Asynchronous Central Above-corridor Floor15 Single Asynchronous Central Above-bench Ceiling16 Single Asynchronous Central Above-bench Floor17 Multiple Asynchronous Aside Above-corridor Ceiling18 Multiple Asynchronous Aside Above-corridor Floor19 Multiple Asynchronous Aside Above-bench Ceiling20 Multiple Asynchronous Aside Above-bench Floor21 Multiple Asynchronous Central Above-corridor Ceiling22 Multiple Asynchronous Central Above-corridor Floor23 Multiple Asynchronous Central Above-bench Ceiling24 Multiple Asynchronous Central Above-bench Floor
31
◼ Evaluation of the design scenarios
◼ Pollutant source positions (focus on fugitive emission)
◼ Gas species
• Acetone
• Dimethyl Ether
◼ Minimum safety level
• PEL?
◼ Evaluation zone (focus on breathing zone)
Bench-topNear door
Bench-topAway from door
Evaluation zone
32
◼ Balance of ACH reductions and pollutant concentration
◼ ACH reductions (energy saving)
Level 1 – Current ACH level
Level 2 – Slight ACH reduction
Level 3 – Moderate ACH reduction
◼ Pollutant concentration control (user safety)
Steady simulations – Normalized mass fraction of pollutants (Cnormalized) and Local mean age of air (τzone)
Transient simulations (selected scenarios) – Dilution time of pollutants (Tdilution)
𝐶𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 =𝐶 − 𝐶𝑠𝑢𝑝𝑝𝑙𝑦
𝐶𝑒𝑥ℎ𝑎𝑢𝑠𝑡 − 𝐶𝑠𝑢𝑝𝑝𝑙𝑦=
𝐶
𝐶𝑒𝑥ℎ𝑎𝑢𝑠𝑡
𝑇𝑑𝑖𝑙𝑢𝑡𝑖𝑜𝑛 = 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 - 𝑇𝑡ℎ𝑟𝑒sℎ𝑜𝑙𝑑
τ𝑧𝑜𝑛𝑒 =𝑀
𝑄
(1)
(2)
(3)
Source: Etheridge & Sandberg, 1996 33
Section 5
Conclusion
◼ Challenges and concerns in the future study
◼ Safety threshold:
• Irregular risks associated with airborne chemicals in the laboratory
• Safety versus energy saving
◼ Laboratory design:
• Simplified models versus complicated lab environments
• Selection/filter of key design parameters
◼ CFD simulations limitations:
• Huge number of scenarios - super computer (HPC) required
• Limitations of opportunities to validate CFD model with measurements
• LES simulation method to capture the unsteady nature of flow – computationally expensive
Source: Sweet & Stuart, 2013 35
HE Yueyang (Dr.), Department of Building, [email protected]
Daniel HII Jun Chung (Dr.), School of Design & Environment, [email protected]
WONG Nyuk Hien (Prof.), Department of Building, [email protected]
PECK Thian Guan (Dr.), Office of Safety Health and Environment, [email protected]
Thank you!
Questions
mailto:[email protected]:[email protected]:[email protected]:[email protected]