MODULE 5 HVAC FUNDAMENTALS OF MODERN LABORATORY DESIGN

Transcription

1 MODULE 5 HVAC FUNDAMENTALS OF MODERN LABORATORY DESIGN Module 5 PG1

2 MODULE 5 GOAL Provide a fundamental understanding of Laboratory Heating, Ventilating and Air Conditioning Concepts and Systems Module 5 PG2

3 Module 6 Outline Issues Drivers Concepts Systems Module 5 PG3

4 Module 5 Issues Some of the most common concerns of laboratory facility users are relative to the HVAC system, including: It s too hot and humid in my lab! It s too cold and dry in my lab! It s like a tornado in my lab! Module 5 PG4

5 Module 5 Drivers Laboratory Equipment Heat Generation Air Change Rates Containment Equipment Occupant Gowning Requirements Type of Laboratory and Science Module 5 PG5

6 Module 5 Drivers Laboratory Equipment Heat Generation Heat Generation Information Heat is expressed in BTU/Hour 1 Watt = BTU/Hour Sensible Heat: Energy Required to Change Temperature Latent Heat: Energy Required to Remove Moisture One Ton of Air Conditioning: 12,000 BTU/Hour or 3,515 Watts 135 cfm of outside air equals 1 ton of cooling (Kansas City weather) Module 5 PG6

7 Module 5 Drivers Laboratory Equipment Heat Generation Loads for Bench Mounted Equipment (low density) Item Bench L.F. Btuh Optical Microscope Analytical balance 2 24 Computer & Monitor Rotary Evaporator Total Btuh Per Linear Foot 87 Watts per linear foot 26 Sources: ASHRAE 2001 Fundamentals Handbook Labconco Catalog Revco Freezer Data Sheets NOTE: This is heat release, not equipment nameplate electrical data Module 5 PG7

8 Module 5 Drivers Laboratory Equipment Heat Generation Loads for Bench Mounted Equipment (high density) Item Bench L.F. Btuh Optical Microscope Small Centrifuge Thermal Cycler Fluorescent Microscope Flame Photometer Rotary Evaporator Total Btuh Per Linear Foot 189 Watts per linear foot 55 Sources: ASHRAE 2001 Fundamentals Handbook Labconco Catalog Revco Freezer Data Sheets Module 5 PG8

9 Module 5 Drivers Laboratory Equipment Heat Generation Loads for Floor Mounted Equipment (high density) Item Floor L.F. Btuh Ultra Low Freezer Large Centrifuge Large Incubator Refrigerator Total Btuh Per Linear Foot 924 Watts per linear foot 271 Sources: ASHRAE 2001 Fundamentals Handbook Labconco Catalog Revco Freezer Data Sheets Module 5 PG9

10 Module 5 Drivers Laboratory Equipment Heat Generation Two Module Lab Example (484 SF): 16 feet of space allocated for floor mounted equipment 48 feet of bench space Assume half the bench is full 24 of equipment Heat Generated using moderate density: Bench: 138 btuh/ft X 24 = 3312 btuh Floor: 662 btuh/ft X 16 = 10,592 btuh Total: *13,904 btuh More than 1 ton of A/C Using 100% outside air in Kansas City: 57,300 btuh (4.75 tons) *There is no diversity in this number Module 5 PG10

11 Module 5 Drivers Laboratory Equipment Heat Generation When figuring equipment heat gain: Use published or measured heat release information, not electrical nameplate Apply diversity carefully based on expected lab use Consider sub-metering loads in similar buildings prior to planning a new lab The answer is not 10 watts/sq.ft. Module 5 PG11

12 Module 5 Drivers Air Change Rates 1 Air Change per Hour The Amount of Air in Cubic Feet per Minute (CFM) it Takes to Completely Replace the Air in a Laboratory once in One Hour CFM = (Floor Area x Ceiling Height x Air Change Rate)/ CFM per One Ton of Cooling Standards and Guidelines Vary from 4 to 12 AC/hr Module 5 PG12

13 Module 5 Drivers Air Change Rates 2 Module Laboratory (22 x 22 ); 484 SF CFM Requirement for varying ceiling heights and air change rates MORE IS NOT NECESSARILY BETTER Airflow in CFM at Given Air Change Rate Ceiling Height Module 5 PG13

14 Module 5 Drivers Air Change VS. Fume Hoods 2 Module Laboratory (22 x 22 ); 484 SF CFM Requirement for varying ceiling heights and air changes Airflow in CFM at Given Air Change Rate Ceiling Height Nominal Fume Hood CFM 5' Fume Hood 6' Fume Hood 8' Fume Hood 960* 1180* 1660* 610** 750** 1060** * Sash full open; face velocity 100 fpm ** Sash at 18 ; face velocity 100 fpm Module 5 PG14

15 Module 5 Drivers Containment Equipment Approximate Exhaust CFM for 6 BSC Class II Type A2 Cabinet without canopy: 0 cfm Class II Type A2 Cabinet with canopy: cfm Class II Type B2 Cabinet : 1150 cfm (requires a dedicated exhaust fan Select the correct cabinet for the application Cabinets that use ECM motors have significantly lower heat gain and higher efficiency than PSC motors Module 5 PG15

16 Module 5 Drivers Air Changes VS. Containment Equipment *Laboratories often use 4 to 6 times more energy per sq. ft. than a typical office building *Nearly half of electrical energy used in a laboratory building can be attributed to ventilation The decision on air exchange rates and fume hood sash position affect both first cost and lifetime building energy costs Annual electricity use in Louis Stokes Laboratory, National Institutes of Health, Bethesda, MD Courtesy of Labs 21 *Courtesy of Labs 21 Module 5 PG16

17 Module 5 Drivers Gowning/PPE Impact of Gowning/PPE in Laboratory May require reduction in Laboratory Design Temperature Reducing Design Temperature from 72 deg. F to 70 deg. F results in: A 12% increase in cooling airflow A 12% increase in cooling capacity Module 5 PG17

18 Module 5 Drivers Type of Laboratory/Type of Science Animal Holding Rooms 10 to 15 Air Changes per hour Module 5 PG18

19 Module 5 Drivers Type of Laboratory/Type of Science Instrument/Computational Laboratories High Equipment Heat Loads Module 5 PG19

20 Module 5 Drivers Type of Laboratory/Type of Science Chemistry/Analytical Laboratories High Fume Hood Density Module 5 PG20

21 MODULE 5 BASIC CONCEPTS Laboratory Hazards Containment Flexibility & Redundancy Module 5 PG21

22 Module 5 Concepts Laboratory Hazards Health Hazards Irritants Corrosive Substances Allergens Asphyxiants Carcinogens Reproductive Toxins Neurotoxins Flammability Hazards Reactivity Hazards Explosive Hazards Biohazards Radioactive Hazards Module 5 PG22

23 Module 5 Concepts Containment Primary Containment First Level of Containment; typically a containment device: chemical fume hood, biological safety cabinet, etc. Module 5 PG23

24 Module 5 Concepts Containment Secondary Containment Second Level of Containment: Laboratory Envelope Directional Airflow 100% Outside Air Differential Pressure or Volumetric Offset Doors must be kept closed Exhaust fans run continuously Best Practices: Use Primary and Secondary Containment to Protect Personnel from Exposure to Hazards ANSI Z9.5 requires air movement from lower hazard to higher hazard Module 5 PG24

25 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods Bench Mounted Chemical Fume Hoods Each Fume Hood uses as much energy as an entire house* * From Labs 21 Module 5 PG25

26 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods Floor Mounted Chemical Fume Hoods or Ventilated Enclosures Module 5 PG26

27 Primary Containment Devices - Chemical Fume Hoods Floor Mounted Hood Location is Critical Module 5 PG27

28 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods Radioisotope Hood Stainless steel interior Requires dedicated exhaust fan Coved corners for decontamination May need HEPA filters Consult your Radiation Safety Officer Module 5 PG28

29 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods Perchloric Acid Hood Acid resistant interior Dedicated acid resistant ran Acid resistant sealed ductwork Washdown system Treat wastewater from washdown Do NOT manifold these hoods Module 5 PG29

30 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods Variable Volume Fume Hood Face velocity is maintained constant as sash is raised and lowered Requires pressure independent control device Requires variable control usually exhaust air bypass damper Must maintain a minimum flow when sash is fully closed (ANSI Z9.5 no longer specifies how much) Module 5 PG30

31 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods High Performance Fume Hood Hood provides containment at lower face velocity Each manufacturer uses a different design Apply with caution Low Flow does not necessarily equate to High Performance More sensitive to cross drafts Labconco Lawrence Berkeley Labs Module 5 PG31

32 Module 5 Concepts Containment Primary Containment Devices - Chemical Fume Hoods Ductless Fume Hood Uses activated carbon and/or HEPA filters Use only in tightly controlled conditions NFPA 45 allows only for nuisance vapors & dusts Module 5 PG32

33 Module 5 Concepts Containment Primary Containment Devices Biological Safety Cabinets Personnel protection Environmental protection Can provide product protection Not a chemical fume hood!!!! Used for biological/microbiological work Module 5 PG33

34 Module 5 Concepts Containment Biological Safety Cabinets (BSC s) Class I: Ventilated cabinet for personnel and environmental protection. No product protection Class II: Ventilated cabinet for personnel, product, and environmental protection. Type A1, A2, B1, and B2 Class III: Totally enclosed ventilated cabinet of leak-tight construction. Operations conducted through attached rubber gloves. Sometimes called glove boxes. Select the correct cabinet for the application Module 5 PG34

35 Module 5 Concepts Other Devices (Non Containment) Other Devices Not Chemical Fume Hoods Canopy Hoods Snorkels Slot Hoods Module 5 PG35

36 Module 5 Concepts Other Devices (Non Containment) Other Devices Canopy Hoods Not appropriate for fumes Hot applications only (ovens, GC/MS, non-hazardous hot tanks, glassware washing, cage washing, etc.) Must have mass of hot moving air to contain Module 5 PG36

37 Module 5 Concepts Other Devices (Non Containment) Other Devices Snorkel Hoods Bench top activities that require exhaust Ideal containment device for dissections Good for bench top soldering, etc. Module 5 PG37

38 Module 5 Concepts Flexibility and Redundancy Three truths for the Laboratory HVAC Designer What s happening in the laboratory tomorrow will be different than what s happening today Fume hood density nearly always increases over time The amount of heat generating equipment will increase over time Module 5 PG38

39 Module 5 Concepts Flexibility and Redundancy Plan for flexibility and future growth Allow extra space in the mechanical room to add equipment (chiller, boiler, air handler, exhaust fans) Allow for additional shaft and ceiling space Size ducts and pipe for spare capacity (inexpensive if done initially) Module 5 PG39

40 MODULE 5 SYSTEMS HVAC Module 5 PG40

41 Module 5 Systems HVAC Laboratory HVAC Look at three different criteria and choose worst case: Cooling load (primarily heat generating equipment) Minimum air change rate Exhaust requirement Consider supplemental cooling for high density loads (freezer rooms, etc.) Module 5 PG41

42 Module 5 Systems HVAC Laboratory HVAC Design Considerations The effect of room air challenge is significant and of the same order of magnitude as the effect of face velocity Consequently, improper design of replacement air supply can have a disastrous effect on the efficiency of a laboratory hood. ASHRAE RP-70, Caplan and Knutson, 1977 Module 5 PG42

43 Module 5 Systems HVAC Laboratory HVAC Design Considerations Supply air distribution shall be designed to keep air jet velocities less than half, preferably less than one-third of the capture velocity or the face velocity of the laboratory chemical hoods at their face opening. ANSI/AIHA Z , section Module 5 PG43

44 Module 5 Systems HVAC Laboratory Exhaust Systems Fan discharge design must minimize risk of re-entrainment Stack/Intake separation Stack height Stack effective height/momentum Stack discharge velocity must be 3,000 fpm, minimum Module 5 PG44

45 Module 5 Systems HVAC Laboratory Exhaust Systems Heat Recovery Air to air plate heat exchanger Run around loop Molecular sieve enthalpy wheel Module 5 PG45

46 Module 5 Systems HVAC Laboratory Exhaust Systems ANSI/ASHRAE/IESNA Prescriptive path requires some combination of VAV and/or heat recovery for most lab HVAC systems Alternative is Energy Cost Budget Method Module 5 PG46

47 Module 5 Systems HVAC Laboratory Exhaust Systems ANSI/ASHRAE January, 2011 interpretation precludes using any technology for laboratory fume hood or chemical storage room exhaust heat recovery that results in any amount of cross contamination This appears to disallow the use of total energy recovery wheels Addendum K is out for public review Module 5 PG47

48 Module 5 Systems HVAC COURTESY OF LABS 21 Module 5 PG48

49 Module 5 Systems HVAC How Much Mechanical Space? Between 8 and 20% of gross building square footage 8% for simpler academic buildings 20% for complex labs or buildings with animal areas Vivariums or BSL containment labs may require 50% of the gross building area for mechanical space Module 5 PG49

50 Module 5 Systems HVAC Applicable Standards and Guidelines Module 5 PG50