The University of Texas at Austin Spring 2012

Course: Field Measurements: Building Energy and IEQ

CE 397

Instructor: Dr. Novoselac, AtilaECJ 9.236Office (512) 475-8175 e-mail: atila@mail.utexas.eduhttp://www.ce.utexas.edu/prof/Novoselac

Office Hours: Tuesday and Thursday 11:00 – 12:00 p.m.

Objectives

• Introduce the course– Motivation

– Schedule

– Evaluation

– Logistics

• Describe other syllabus content

• Address any of your concerns

Introduce yourself

• Name?

• Grad/undergrad?

• Department?

• Your professional interest?

Motivation for taking this course

• Experimental part of your MS/PhD work

• Building commissioning

• Forensic engineering studies

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 Objectives

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

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Course Topics

• There is no required textbook

Instead

• Course notes

• Handouts• Hard or electronic copies of reading materials

– Book sections

– Journal papers

– Instrument manuals

Textbook

Grading

• Midterm Test 20%• Classroom Participation 10%• Homework Assignments 40%• Final Project & Presentation 30%

100%

Test (20%)

In-class exam

Based on: • 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

• …..

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Final project (30%)

• Independent study related to• your research topic or• a forensic engineering problem

• Will include • lab and field measurement • results processing and analysis• report writing • presentation in class

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Logistics

• 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/

• Class notes • Electronic handouts• Assignments• Grades

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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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PRC fasciitis

• 5 Laboratories in building: PRC 133• UTest house

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133

Field measurement

In the second part of the course • 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• 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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• Introduction to lab and field work, examples• Terminology

Class Topics for today

Lab Measurement • Strictly design experiments• Focus on maintaining one group of parameter in a

controlled environment to measure other

• Motivation:• 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

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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 Room dimensions

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Convection Correlation Development Experimental Design

q [W/m2]

Tair

Flow rate [ACH]

Air velocity

h=f(Tsurf-Tair_local)

h=f(ACH)

Measured permeates:- Heat flux- Surface temperature - Air temperature - Supply air temperature- Flow rate- Air velocity

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Test room:

- Strict energy and mass balance

- Steady state condition

Instrumentation:

• Heat flux (power meter)

• Temperatures (thermistors)

• Flow (pressure based flow station)

• Velocity (hot wire)

Data acquisition

Convection Correlation Development Instrumentation:

Velocity sensorsThermistors

Floor

Air

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Convection Correlation Development Sensitivity analysis results:

Effect of temperature Effect of flow rate

Q=A·h_temp_based·(Tsurf-Tair_local) Q=A·h_flow_based·(Tsurf-Tsupply_air)

Convection correlation expressed as a function of volume flow rate is stronger than correlation expressed as a function of temperature

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Convection Correlation Development Results

In our cases we had turbulent flowh ~ 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:• Accuracy: ±1.5% of full scale

• Repeatability: ±0.5% of full scale

Instrument 2:• Accuracy: ±1.5 % of reading (limited in certain range)• Repeatability: ±0.5%

• 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

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Other things that you should care about

Sensitivity• Sensitivity of the

sensor is defined as the slope of the output characteristic curve

Thermistors

Resistor

Temperature range

Which one is more sensitive?

Other things that you should care about

• Response time

Can be defined for other % values

Standard definition

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?

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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?

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

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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

(Some) Real World Concerns

• First and operating cost• Ease of use• Safety• Durability• Flexibility• Reliability• Power requirements• Environmental requirements/conditions