Power Up!-Get Energized

Materials 1/4 inch copper tubing Copper flare nuts Solder Syl fos-dynaflo (silvabraze) Paste flux Soapsuds Emery cloth *********************             Window air conditioners Working refrigerators Evaporative Coolers

Tools 45˚ flaring block & yoke Tube cutter Tube bender 1/4" Swaging punch Propane canister & tip MAPP gas canister & torch tip Eye protection Flame striker Solder torch & tip Map gas & torch tip hammer pliers heat proof pad vice airline with air pressure reduced to 20 psig 1/4' flair-nut adapter for airline flux brush soapsuds brush ******************** philips screwdrivers slotted screwdrivers square bit drivers extension cords watt meters pressure gauge manifold thermocouples & meter anemometer Relative humidity meters

Assessment Plan

Refrigeration and society research paper
     Shanghai worksheet
     Air conditioner take-apart lab
     Responsible buying of a cooling unit presentation
     Cooling system lab with lunch
     Evaporative cooling sketch and lab
     Brazing hands-on activity
     Cooling options trade-off chart

Teach (How to teach it?)

Anticipatory Set

Reading

Excerpts from Laura Ingalls Wilder's  Little House Series : Farmer Boy (1933) [Chapter 6: Filling the Ice-House, pp.65-74], The Long Winter (1940) [Chapter 3: Fall of the Year, pp.27-31].

Excerpts from The Frozen Water Trade by Gavin Weightman (2003) [Introduction, pp.1-12; Chapter 4: Exile in Havana, pp.62-72; Chapter7: The Cutting Edge of the Ice Trade, pp. 105-111]

Lecture

Concern with cooling because of

1. food preservation
2. vaccine, drug, donor organ preservation
3. building and comfort cooling
4. political/social concerns over energy distribution energy and social justice

 

Introduction to Unit

Lecture

Overview unit goals
            Difficulty of transferring heat against its natural direction.
            The state of technology- how can one cool space?

Assign: Refrigeration and society  research paper

 

Cooling based on changing phases 

Reading Resources:

The Distance We've Come by Henry Petroski
     http://www.memagazine.org/backissues/membersonly/january2000/features/distance/distance.html

It's a cool story! by Bernard Nagengast
     http://www.memagazine.org/backissues/membersonly/may00/features/coolstory/coolstory.html

Choosing the right refrigerant by Siva Gopalnarayanan
     http://www.memagazine.org/backissues/membersonly/october98/features/refrig/refrig.html

Refrigeration and Global Warming by Siva Gopalnarayanan
     http://www.memagazine.org/backissues/october98/features/refrig/global.html

 

Lecture & Discussion

Pressure, temperature and phase of a material

      Measurement : (gauges, thermocouples, thermometers) What is psi, ˚F, ˚R, ˚C, K?

Power units : Watts, Btu/hr

        How do we measure power? Electricity vs. Heat Transfer

     Types of cooling units based on phase change: categorized by application, temperature range and capacity

     Working fluids, limitations & issues.

Internet Exercise

Power requirements & Economics - Shanghai worksheet

 

1st and 2nd Laws of Thermodynamics

Reading Resources:

Chapter .

Lecture

Energy cannot be created or destroyed, only transferred. (1st law)

Impossible to create order from disorder spontaneously. (2nd law)

Thermal equilibrium, the notion of disorder and an introduction to entropy.  

Changing phases is an effective way to move heat.

      Heat always moves from higher to lower temperatures.

Parts of a vapor compression cycle.

      Evaporators: Heat- in, breaking weak chemical bonds takes energy

      Condensers: Heat-out, forming chemical bonds releases energy

      Compressors: Work-in, pushing molecules together takes energy

      Capillary tube

Lab

Air conditioner take-apart lab

Group work

Assign: Responsible buying of a cooling unit presentation

Simulation

Run the NC simulation.

North Carolina State University presents Air Conditioning and Refrigeration

Guided Discussion

Commercial Development

    Types of evaporators (reach-in cooler units for flowers, food, etc., roll bond and holdover plates)

    Types of condensers (air-cooled, water-cooled)

    Types of compressors

    Other components: valves, filter driers, accumulators, sight glass; What are they for and why are they included?

Lab

Cooling system lab with lunch

 

Alternative Cooling Technologies

Reading:

Chapter.

Lecture / Discussion

Ideas behind passive cooling

Human comfort and humidity

Evaporative cooling

Geothermal cooling

Advanced ideas to minimize energy: Absorption chillers, use of desiccants.

Group

Evaporative cooling sketch and lab

 

Hands-on Build

 Lab

Building a safe system
     Discussion of joints: threaded, soldered.

Directions / guidance
     Brazing hands-on activity

 

Summary / Closure

Lecture

Using a trade-off chart to compare and contrast available technologies.

Group

Cooling options trade-off chart

Discussion Questions

    Why does a freezer require electric energy to operate?

    Why does an air-conditioner have an indoor and outdoor component?

    What are the challenges facing the refrigeration industry?

    Can we meet the world's needs for cooling?

    How does refrigeration impact the environment?

    Do you feel you are a more informed citizen after this unit? Why?

 

Challenge

Explore the current state of US energy production and supply.
     http://www.worldwatch.org/

 

Post-teach (Did we succeed?)

Evaluation Criteria

Cooling system lab with lunch
     Evaporative cooling sketch and lab
     Shanghai worksheet
     Air conditioner take-apart lab
     Responsible buying of a cooling unit presentation
     Refrigeration and society research paper
     Cooling options trade-off chart

Resource List

Text Reference for Lectures

• Cengel, Y.,  Boles, M. , Thermodynamics An Engineering Approach 4th Edition (2002) McGraw-Hill Ed. NY. ISBN 0-07-238332-1
• Bloomfield, L., How Things Work, The Physics of Everyday Life 2nd Edition. (2001) John Wiley & Sons, NY. ISBN 1-471-38151-9.

Refrigeration & Air-Conditioning Resources

	American Society of Heating, Refrigeration and Air Conditioning Engineers, Inc. (ASHRAE)
	Air Movement and Control Association, Inc. (AMCA)
	NC State University "Air Conditioning & Refrigeration " Tutorial	www.ncsu.edu/cpe
	Holdover plates and roll bond evaporators	http://www.rparts.com
	Refrigeration supplies- Gustave Larson Company	http:/www.galarson.com
	United Refrigeration Inc.	www.uri.com

---

ME Too! Mechanical Engineering for Everyone - Last Updated: 11/12/2006
Partner Institutions: University of St. Thomas and College of St. Catherine    The research underlying this curriculum
was supported by the National Science Foundation under grant ESI-0341897.