CE/ARE 397 Indoor Air Quality: Field Measurements

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The University of Texas at Austin
Course:
Spring 2012
Field Measurements: Building Energy and IEQ
CE 397
Instructor:
Dr. Novoselac, Atila
ECJ 9.236
Office (512) 475-8175
e-mail: [email protected]
http://www.ce.utexas.edu/prof/Novoselac
Office Hours:
Tuesday and Thursday 11:00 – 12:00 p.m.
Objectives
• Introduce the course
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Motivation
Schedule
Evaluation
Logistics
• Describe other syllabus content
• Address any of your concerns
Introduce yourself
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Name?
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Grad/undergrad?
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Department?
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Your professional interest?
Motivation for taking this course
• Experimental part of your MS/PhD work
• Building commissioning
• Forensic engineering studies
Course Objectives
1. Gain an appreciation for field and laboratory measurements
relevant to: building energy performance and indoor
environmental quality.
2. Learn about measurement techniques, instrumentation and
complexities associated with their use (including accuracy
and interference issues).
3. Obtain hands-on experience (in lab and field) with a number
of basic instruments used in field investigations of buildings.
4. Analyze data from field and laboratory measurements and
assess performance of buildings and their components.
Course Topics
1. Course introduction and lab and field work safety
1 wk
2. Specifics of field and laboratory measurements
1 wk
3. Experimental error & quality control
2 wks
4. Velocity, flow, and pressure measurements
2 wks
5. Temperature, humidity, and heat and moisture flows
2 wks
6. Measurement of particulate matter
1 wk
7. Measurement of gaseous contaminants
1 wk
8. Electric power measurement
1 wk
9. Signal processing and data acquisition
1 wk
10. Sample collection and analysis
2 wks
Total 14 wks
6
Textbook
• There is no required textbook
Instead
• Course notes
• Handouts
• Hard or electronic copies of reading materials
– Book sections
– Journal papers
– Instrument manuals
Grading
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Midterm Test
Classroom Participation
Homework Assignments
Final Project & Presentation
20%
10%
40%
30%
100%
Test (20%)
In-class exam
Based on:
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readings
lectures
assignments
lab and field measurements
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Participation (10%)
• Come to class and participate in measurements
• Let me know about class(es) you will miss
• Read assigned articles and contribute to
discussion
• Submit homework assignments in time
• Participate as a team member
• Handle equipment properly
Homework Assignments (40%)
• Calculation assignments
• Measurement result processing
• Correlation development
• …..
11
Final project (30%)
• Independent study related to
• your research topic or
• a forensic engineering problem
• Will include
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lab and field measurement
results processing and analysis
report writing
presentation in class
12
Logistics
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Course website
Class location and times
PRC facilities
Field trips/measurements
Laboratory demonstrations
Equipment
Data analysis/record keeping
Safety
Website
http://www.caee.utexas.edu/prof/Novoselac/classes/CE397/
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Class notes
Electronic handouts
Assignments
Grades
14
Class Location
• This classroom
• 50% of class time
• Pickle Research Center labs and UTest house
• 30% of class time
• Field events
• 20% of class time
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15
PRC fasciitis
• 5 Laboratories in building: PRC 133
• UTest house
133
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Field measurement
In the second part of the course
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A campus building
Facade thermal lab at UT School of Architecture
City of Austin fire department facilities
Pecan Street Project test house
Other residential and commercial buildings
• You are welcome to suggest a location
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Schedule
I need your availability for classes in PRC
Filed trips will be scheduled in advance
- 10 to 15 days in advance
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Lab and UTest house
demonstrations
• Primarily me
• Other faculty
• BEE graduate students
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Equipment
• Equipment for field assignments should be
organized at least a day before the assignment
• All students are responsible for checking
equipment in and out and returning it to lab
• All equipment should be treated gently and any
issues brought to my attention
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Data analysis/record keeping
• Students are responsible for handling all the
lab and filed work data
• You will need:
• Lab/field note books
• Flash drives for electronic data transfer
• Installed some of the equipment software on your
computer
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Safety
• Clothing
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Clothes that you don’t care about
Nothing flowing
No exposed skin except haands
Close-toed shoes
• UT EH&S (Laboratory) Safety Training (by the end
of the next week)
• http://www.utexas.edu/safety/ehs/lab/
• http://www.utexas.edu/safety/ehs/train/oh101.html
• http://www.utexas.edu/safety/ehs/train/oh201.html
Other issues
• Course history
• Course work load
• Visiting lecturer
• Your questions ?
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Class Topics
for today
• Introduction to lab and field work, examples
• Terminology
Lab Measurement
• Strictly design experiments
• Focus on maintaining one group of parameter in a
controlled environment to measure other
• Motivation:
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Mimic real environment for measuring certain phenomena
Testing of product or technology
Model development
Validation
…..
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Field Measurements
• Often the only way to document the real world
• Often conducted in conjunction with
laboratory measurements
• Many phenomena can not be meaningfully
modeled or reproduced in the laboratory
Example of Lab Work:
Convection Correlation Development
Heat transfer at floor in a room with displacement ventilation
Q=A·h·ΔT
h=f( air velocity, temperature difference , geometry )
V or ACH
Tsurf-Tair
or Tsurf-Tsupply
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Room dimensions
Convection Correlation Development
Experimental Design
h=f(Tsurf-Tair_local)
h=f(ACH)
Air velocity
Tair
q [W/m2]
Flow rate [ACH]
Measured permeates:
- Heat flux
- Surface temperature
- Air temperature
- Supply air temperature
- Flow rate
- Air velocity
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Convection Correlation Development
Instrumentation:
Test room:
- Strict energy and mass balance
- Steady state condition
Velocity sensors
Thermistors
Air
Instrumentation:
• Heat flux (power meter)
• Temperatures (thermistors)
• Flow (pressure based flow station)
• Velocity (hot wire)
Data acquisition
Floor
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Convection Correlation Development
Sensitivity analysis results:
Effect of temperature
Q=A·h_temp_based·(Tsurf-Tair_local)
Effect of flow rate
Q=A·h_flow_based·(Tsurf-Tsupply_air)
Convection correlation expressed as a function of volume flow rate
30 is stronger
than correlation expressed as a function of temperature
Convection Correlation Development
Results
In our cases we had turbulent flow
h ~ velocity0.8 ~ ACH0.8
Function fitting:
least square method
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Example of Field Work:
Energy Implications of Filters
• Does using a better filter increase energy use?
• Conventional wisdom: Yes
• For smaller buildings: Maybe not
• Flow, fan energy, system energy, SHR, AC capacity
• All DECREASE
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Experimental Design
• Why can’t this study be done in a laboratory?
• Monthly measurements in 17 buildings over
the course of a year with different filters
installed
• Additional measurements in test house
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Instrumentation
• Power draw
• Fan and compressor
• Pressure drop
• Filter and coil
• Temp. and RH
• Capacity
• Fan flow
• Duct leakage
• Major issue?
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Summary
• Fieldwork is very messy
• Confounding variables and outliers
• Need large sample sizes
• Expensive and time consuming
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Terminology
• What is the difference between accuracy and
precision?
• Note that these terms are often confused and conflated with
other terms
• Accuracy – “Capability of an instrument to indicate
the true value of a measured quantity.”
• Precision – “Repeatability of measurements of the
same quantity under the same conditions; not a
measure of absolute accuracy”
• Precision not often reported
Reference ASHRAE Guideline 2
Terminology
• Example of accuracy and precision:
High accuracy,
low precision
Low accuracy,
High precision
Good measurement result is both: accurate and precise
Some Comments about
Instrument Accuracy
• Manufacturers are almost always optimistic
• Make the difference between accuracy defined for
full scale and reading
Instrument 1:
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Accuracy: ±1.5% of full scale
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Repeatability: ±0.5% of full scale
Instrument 2:
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Accuracy: ±1.5 % of reading
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Repeatability: ±0.5%
(limited in certain range)
• What is Repeatability?
Some Comments about
Instrument Accuracy
• Accuracy is rarely constant over Range
• Assume frequent calibration
• Requires standard
• Calibrate over range of interest
• Don’t use complicated calibration curves
• Anything other than linear requires justification
• Consider arrangement with multiple sensors
Other things that you should care
about
Sensitivity
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Thermistors
Sensitivity of the
sensor is defined as
the slope of the
output characteristic
curve
Resistor
Temperature range
Which one is more sensitive?
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Other things that you should care about
• Response time
Standard
definition
Can be defined for other % values
Other things that you should care about
• Response time
• Hobo U12 internal temperature sensor
• Response time in airflow of 1m/s (2.2mph)
• 6 minutes, typical to 90%
• Telaire 7001 CO2 sensor
• <60 seconds to 90% of step change
• How do you use these values?
Other things that you should care
about
Hysteresis
• Sensor should follow the
changes of the mesured
parameter regardless of
which direction the
change is made; hysteresis
is the measure of this
property
How this affects the instrument accuracy?
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Other things that you should care about
Resolution
• the smallest detectable incremental change of input parameter that can be
detected in the output signal
• Hobo U12 internal relative humidity sensor
• 0.03% RH
• Telaire 7001 CO2 sensor
• ±1 ppm
• How do you use these values?
• Note that resolution can be limited by data logger
Other things that you should care about
• Range and detection limit
• How do you use these values?
• Note that you are often trading off range and
resolution and/or accuracy
• Example:
• Measuring CO2 with
Telaire 7001 CO2 sensor
Other things that you should care
about
Example:
In our test house we use CO2 as tracer gas
We use Telaire 7001 CO2 sensor for
concentration measurement
What is the range accuracy
and detection limit?
http://www.microdaq.com/telaire/index.php
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(Some) Real World Concerns
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First and operating cost
Ease of use
Safety
Durability
Flexibility
Reliability
Power requirements
Environmental requirements/conditions
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