Heat Transfer in Architecture: Convection

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Objective

SWBAT test a geo thermal heating systems and describe how convection as a heat transfer has an impact on home heating.

Big Idea

How do the designers of geo thermal heating use the science concept of heat transfer to design eco-friendly building systems? Students complete an investigation as they explore geo thermal convection systems.

Preface

3 minutes

This investigation is intended to be a part of my lesson Designing an Eco Friendly Building, which introduces the idea of geo-thermal heating. My students research geo-thermal heat transfer heating systems so they have important background information. If you would like to use this as a stand alone investigation, I would suggest teaching the lesson Heat Transfer in Architecture, which introduces the concepts of convection, conduction, and radiation as they apply to architecture. 

Furthermore, this investigation can be conducted simultaneously with my two other heat transfer investigation lessons:Heat Transfer in Architecture: Conduction, and Heat Transfer in Architecture: Radiation. The advantage of doing all three investigations together is there is no need to have multiple testing models. The disadvantage is the safety issue in the Heat Transfer: Convection Investigation, in which there is a hot plate or a Bunsen Burner. When I run all three at the same time, I devote my energy to the investigation with the largest safety risk. 

Design the Investigation

10 minutes

My instructional strategy is Testing a Model.  I begin by showing all the equipment to the students and begin my questions. "What do you think we should investigate?" Students begin to respond and I continue questioning them, easing them into the problem, "I want to find out if time has an effect on the temperature." I then ask, "What should we measure and how should we record it?" The class begins to understand that we will measure the temperature and the time. I ask, "Which is the dependent/independent variables? What are some constants or controls we should consider?" I use the information the students determine to create the investigation. The first part looks like this: 

  1. Problem:  I want to find out if time has an effect on the temperature.
  2. Hypothesis: What do you think?       
  3. Procedure: Steps to Creating Perfection
    • Measure the temperature at 0 seconds.
    • Start the heat source.
    • Time every 15 seconds for 1 minute.
  4. Variables
    • Independent variable: time
    • Dependent variable: temperature
    • Controls/Constants: time is the same for all investigations

With these ideas, I give the students the Heat Transfer Lab - Convection. I have typed in all the information we have discussed and given each student a copy. They are ready to record data! 

 

 

Conduct the Investigation

10 minutes

Before we begin the test I ask the students, "Why is this model not a good example of what will happen in real life?" Groups of students talk together to form an answer. I number each person in the group and ask a random number to stand up and share an answer.  Student answers include, "It's not full size. The hand warmer is not a constant temperature. There are cracks between the house and the top of the boot box. The boot box is full or air, not dirt. "

Students go to the model and begin the tests. They record the temperature and the time. I use a Team Responsibility strategy for collecting data. Groups of students assign each person a task. The tasks are Data Recorders, Timers, and Temperature Recorders. The Timer is responsible for calling out the time. The Temperature Recorder calls out the temperature. The others in the group, Data Recorders are all responsible for writing down the data. When the experiment is over, the Data Recorders share the data with the Timer, and Temperature Recorder. 

Time

Temp

15

 

30

 

45

 

60-1 minute

 

1:15

 

1:30

 

1:45

 

2:00 minutes

 

I monitor the recording. There have been times when the hand warmer falls off the rubber tubing so I make sure everything is taped on correctly. I ask students to place a hand on the roof to hold the top down. 

As students are recording data they are making observations. On the second page of the lab, there is a section for observations. I ask students to write observed patterns and possible compromises. 

When the investigation is over I use use a strategy to help students write their conclusions called, Bringing in the Real World.  In this strategy I help students understand how to use the information from the investigation in their conclusions. I ask, "Do engineers, architects and scientists design homes thinking about convection?" The following movie shows how I bring in real world applications to help students write their conclusions. 

Writing a Conclusion

10 minutes

The conclusion question applies to the design of an eco-friendly home. The question I ask students to answer in the conclusion is, "How does convection have an impact on the design of a house?" Before students write the conclusion, I ask, "Does anyone have geo-thermal heating in their homes?"  (I have had one family, which still is amazing to me.) I ask, "What is the heat source in your house?" Students answer, "The furnace." I ask, "In most houses where is the furnace?" "The basement." I ask, "Why?"

Groups of students discuss why they think the furnace is in the basement. I walk around the room and probe groups. "Can you use the word convection?" "What happens to the hot air?" 

Finally, students write their conclusions. I ask students to write a 3-5 sentence summary. They must use data from the investigation to support their conclusion.

I use a strategy called Write to Learn. Students are asked to use science vocabulary from our Word Wall. In addition, they must use the data from the investigation to support their conclusion.