Objectives Complete high-quality projects Understand expectations Control theory and design

“Second Day of Bombing Fails to Bring Peace to Gorazde” Seattle Post Intelligencer: April 11, 1996

Ground Rules 6 pages single-spaced, 12 pt 1 inch margins Excludes references Includes figures and tables No appendices Bottom line – You have to be very concise

Key Words The goal of this project is for you to develop a comprehensive design guide for a specific HVAC component. The design guide should both serve as a reference for HVAC engineers specifying the component, as well as summarize current research on the component.

Objectives/Criteria Locate and use high quality references to solve HVAC design problems Concisely summarize technical material Present technical work in oral and written forms

Questions How do you select this component? What are most important factors? What are typical values of these parameters for residential and commercial HVAC systems? What should designers know about this component? What are the current/recent research issues for this component? What are recent improvements and what benefits do they yield? What will this component look like in 30 years?

Some Cautionary Notes Don’t use others figures and tables Your job is to identify and concisely describe relevant work Papers you are reading serve as good sources for style Consistency is really important –Consistent reference and citation style –Consistency between sections

Grammar and Style Common grammatical and stylistic errors –Colloquial –Articles and prepositions –Overuse of parentheses –Unclear subjects –Long sentences –Not defining terms

Strategies for Avoiding Grammatical Errors Peer review/edit before submission Read paper out loud –Even better (more embarrassing) with an audience Read each sentence, starting from end of paper Look at previous versions to try and catch recurring errors

Written Report Evaluation 10% Thoroughness and utility 15% Depth and justification 15% Answers requested questions 20% Quality of writing and analysis 10% Quality and completeness of references

Oral Presentation Very different than written communication Must be much more concise Must work harder to maintain interest and attention

Preparing an oral presentation Consider your audience Tell a story Mix visuals and text Be selective about what you present –Listeners can read paper if they want more Keep presentation clear and simple Be consistent Don’t ever read from notes or from slides PRACTICE PRACTICE PRACTICE Aim for readability

Consistency Headaches are bad Impairs thought process. Hard to get work done I don’t like it when I have headaches because my brain hurts a lot and I can’t get anything meaningful done. Relatively few fonts, consistent format between slides

Referencing in a presentation Don’t have to give full references Listeners want to know –Who –When –Where 25% headaches hurt Migraine Boy, 1997, J. Traumatic Stress

Random comments Be careful with humor Be cautious about transitions Plan for contingencies Have extra material available Back-up your presentation Extraneous visual material on slides is distractingExtraneous visual material on slides is distracting Misteaks are very obvious to audience Any questions about presentations?

Objectives Terminology Types of controllers –Differences Controls in the real world –Problems –Response time vs. stability

Motivation Maintain environmental quality –Indoor air quality –Occupant comfort –Material protection Conserve energy Protect equipment

History Process controls Self powered controls Pneumatic and electro-mechanical controls Electronic controls Direct Digital Control (DDC)

Terminology Sensor –Measures quantity of interest Controller –Interprets sensor data Controlled device –Changes based on controller output Figure 2-13

Direct Closed Loop or Feedback Indirect Open Loop or Feedforward

Set Point –Desired sensor value Control Point –Current sensor value Error or Offset –Difference between control point and set point

Two-Position Control Systems Used in small, relatively simple systems Controlled device is on or off –It is a switch, not a valve Good for devices that change slowly

Humble Honeywell T87 ~50 years old Innards are deceptively complicated Elegant design Significant patent issues

Anticipator can be used to shorten response time Control differential is also called deadband

Not-So-Humble Chronotherm III DDC – measures temperature many times every second Incorrectly accounted for wall temperature Wide swings in air temperature

Modulating Control Systems Used in larger systems Output can be anywhere in operating range Three main types –Proportional –PI –PID

Proportional Controllers O is controller output A is controller output with no error K P is proportional gain constant e is error (offset)

Very big gain leads to big changes in output and instability Goal is to pick biggest possible gain and still have have a stable system

Stable systemUnstable system

Proportional + Integral (PI) K i is integral gain If controller is tuned properly, offset is reduced to zero Figure 2-18a

Proportional + Integral + Derivative (PID) Improvement over PI because of faster response and less deviation from offset –Increases rate of error correction as errors get larger But –HVAC controlled devices are too slow responding –Requires setting three different gains

Ref: Kreider and Rabl.Figure 12.5

The Real World 50% of US buildings have control problems –90% tuning and optimization –10% faults 25% energy savings from correcting control problems Commissioning is critically important

Practical Details Measure what you want to control Verify that sensors are working Integrate control system components Tune systems Measure performance Commission control systems