On this page, you will learn to apply the concepts of heat transfer you have learned in the previous sections to the heat engineering of buildings. The building models you will play with and construct are 2D and very simple.
Building
Learning goal
❶ Heating and cooling of a house
When you turn on the heater of your house in winter, it takes a while for the whole
house to warm up. When you turn off the heater, it also takes a while for it to cool down.
As the house is constantly losing heat to the environment, the temperature cannot rise further at some
point during heating. This temperature is the equilibrium temperature—the temperature when
energy gain and loss balance in a house.
The equilibrium temperature depends on the heating power and the insulation.
The higher the heating power is, the higher the equilibrium temperature will be. Under the same heating power,
the better the house is insulated, the higher the equilibrium tmeperature will be.
The following simulation is set up for you to test these with a simple 2D house.
Instructions:
In this simulation, there is a heater at the corner of the right part of the house and three thermometers
at different locations (one close to the heater, another far, and the third one outside the house).
- Click "Low" to turn on the heater, click "Run" to start heating up the house,
and click "On" to turn on the temperature graph.
- Wait until the temperatures do not rise as quickly any more. Click "Power Off" and observe how the house
cools down.
- Click "Reset". Click "High" and repeat the heating-cooling test above.
- Change the insulation of the construction material. By default, the simulation uses "Good" insulation.
Click "Reset". Select "Poor" and repeat the heating-cooling test.
Question: (Click the link below to answer)
1) Why does the thermometer outside the house read lower than the others?
2) What happens if the window is open?
3) What happens to a house with poor insulation, compared with good insulation?
To "open" the window, select the window (represented by the white rectangle) and press DELETE on the keyboard.
❷ Convective heating
Convection is an important heat transfer process in a house. You probably find in your house that the heater
is placed near the floor. There is a good reason for that arrangement.
Instructions:
The red circle represents a heater that is maintained at constant temperature.
- Click "Run" and observe the heat flow.
- Click "Reset". Drag the heater around, run the simulation, and see the change of the heat flow.
- Click "Reset". Click the ceiling (the green piece) and press the DELETE key to remove.
And then run the simulation again.
Question: (Click the link below to answer)
1) Which thermometer measures the highest temperature?
2) Does the ceiling help the house keep warm?
❸ Solar heating through a window
A house can gain some heat from the sun through its windows. In winter, we want to maximize this gain.
In summer, we want to minimize this gain.
Instructions:
Use this simulation to explore the solar heating. You can control the direction of sunlight and
observe how the house is heated.
- Click "Run" to start the simulation. Click on the simulation window and press 'q' and 'w'
on the keyboard to change the angle of the sunlight.
- Click Sunlight "On" and "Off" to turn on and off the sunlight.
Note: There are some approximations used in this simulation.
The light rays in the simulation travel in a much slower speed than the speed of light. Also, sunlight
does not divide into a number of rays as shown in this simulation. We also assume that the inner surfaces
of the walls reflect light (a good approximation if the surfaces are painted white). For any outer surfaces,
since their heating contribute little to the interior of the house, light will just bounce off from them.
❹ Building your own 2D house: A design challenge
In this activity, you will draw a 2D house and simulate the energy flow in it.
The following are the instructions:
1. Adding a foundation.
Click "Rectangle" and drag the mouse in the window to draw a rectangle at the bottom.
2. Adding a wall.
Click "Rectangle" and drag the mouse in the window to draw a rectangle.
3. Adding a window.
Click "Rectangle" and drag the mouse in the window to draw a rectangle. Click "Select". Right-click on
the rectangle. Select "Properties" from the pop-up menu. When the "Properties" dialog shows up, set
"Absorption" to be 0 and "Transmission" to be 1 under "Optical properties".
4. Adding a roof.
You can add a rectangle to be a roof if you want to create a flat-top house. For any other shape,
click "Polygon" and draw a polygon. To make a reflective roof, click "Select" and then
right-click on the rectangle. Select "Properties" from the pop-up menu. When the "Properties" dialog
shows up, set both "Absorption" and "Transmission" to be 0 and "Reflection" to be 1 under "Optical properties"
5. Adding a ceiling.
The same as adding a rectangle.
6. Adding a heater.
Click "Rectangle", "Ellipse", or "Polygon" to add an object. Click "Select". Right-click on the object.
Select "Properties" from the pop-up menu. When the "Properties" dialog shows up, select "Constant temperature"
and set the temperature under "Source properties".
7. Others.
You can delete an object by clicking on it and pressing the DELETE key. You can change the properties of
any object by choosing the "Select" mode and right-click on it to access the "Properties" dialog. You
can also access the "Properties" of the entire system by right-clicking on an empty spot to invoke the
pop-up menu. You can add as many thermometers as you need by clicking on "Thermometer" and then clicking
within the window.
8. Save a screenshot of your work. To save a screenshot of your work on Windows,
press the "Print Screen" key on your keyboard and then paste it into the Paint program. Save the image as
a JPEG file and email it to your teacher!
Summary
This page covers a few topics in the heat engineering of a building. First, a building is a thermal system
that is constantly exchanging thermal energy with the environment and can be heated and cooled. Convection
plays an important role on heating and cooling in a house. Solar energy contributes to the heating of a
house.
We need your feedback! Please click
HERE to complete
a short survey.
|
When you turn on the heater of your house in winter, it takes a while for the whole
house to warm up. When you turn off the heater, it also takes a while for it to cool down.
As the house is constantly losing heat to the environment, the temperature cannot rise further at some
point during heating. This temperature is the equilibrium temperature—the temperature when
energy gain and loss balance in a house.
The equilibrium temperature depends on the heating power and the insulation. The higher the heating power is, the higher the equilibrium temperature will be. Under the same heating power, the better the house is insulated, the higher the equilibrium tmeperature will be. The following simulation is set up for you to test these with a simple 2D house. |
|||
|
❷ Convective heating
Convection is an important heat transfer process in a house. You probably find in your house that the heater
is placed near the floor. There is a good reason for that arrangement.
Instructions:
The red circle represents a heater that is maintained at constant temperature.
- Click "Run" and observe the heat flow.
- Click "Reset". Drag the heater around, run the simulation, and see the change of the heat flow.
- Click "Reset". Click the ceiling (the green piece) and press the DELETE key to remove.
And then run the simulation again.
Question: (Click the link below to answer)
1) Which thermometer measures the highest temperature?
2) Does the ceiling help the house keep warm?
❸ Solar heating through a window
A house can gain some heat from the sun through its windows. In winter, we want to maximize this gain.
In summer, we want to minimize this gain.
Instructions:
Use this simulation to explore the solar heating. You can control the direction of sunlight and
observe how the house is heated.
- Click "Run" to start the simulation. Click on the simulation window and press 'q' and 'w'
on the keyboard to change the angle of the sunlight.
- Click Sunlight "On" and "Off" to turn on and off the sunlight.
Note: There are some approximations used in this simulation.
The light rays in the simulation travel in a much slower speed than the speed of light. Also, sunlight
does not divide into a number of rays as shown in this simulation. We also assume that the inner surfaces
of the walls reflect light (a good approximation if the surfaces are painted white). For any outer surfaces,
since their heating contribute little to the interior of the house, light will just bounce off from them.
❹ Building your own 2D house: A design challenge
In this activity, you will draw a 2D house and simulate the energy flow in it.
The following are the instructions:
1. Adding a foundation.
Click "Rectangle" and drag the mouse in the window to draw a rectangle at the bottom.
2. Adding a wall.
Click "Rectangle" and drag the mouse in the window to draw a rectangle.
3. Adding a window.
Click "Rectangle" and drag the mouse in the window to draw a rectangle. Click "Select". Right-click on
the rectangle. Select "Properties" from the pop-up menu. When the "Properties" dialog shows up, set
"Absorption" to be 0 and "Transmission" to be 1 under "Optical properties".
4. Adding a roof.
You can add a rectangle to be a roof if you want to create a flat-top house. For any other shape,
click "Polygon" and draw a polygon. To make a reflective roof, click "Select" and then
right-click on the rectangle. Select "Properties" from the pop-up menu. When the "Properties" dialog
shows up, set both "Absorption" and "Transmission" to be 0 and "Reflection" to be 1 under "Optical properties"
5. Adding a ceiling.
The same as adding a rectangle.
6. Adding a heater.
Click "Rectangle", "Ellipse", or "Polygon" to add an object. Click "Select". Right-click on the object.
Select "Properties" from the pop-up menu. When the "Properties" dialog shows up, select "Constant temperature"
and set the temperature under "Source properties".
7. Others.
You can delete an object by clicking on it and pressing the DELETE key. You can change the properties of
any object by choosing the "Select" mode and right-click on it to access the "Properties" dialog. You
can also access the "Properties" of the entire system by right-clicking on an empty spot to invoke the
pop-up menu. You can add as many thermometers as you need by clicking on "Thermometer" and then clicking
within the window.
8. Save a screenshot of your work. To save a screenshot of your work on Windows,
press the "Print Screen" key on your keyboard and then paste it into the Paint program. Save the image as
a JPEG file and email it to your teacher!
Summary
This page covers a few topics in the heat engineering of a building. First, a building is a thermal system
that is constantly exchanging thermal energy with the environment and can be heated and cooled. Convection
plays an important role on heating and cooling in a house. Solar energy contributes to the heating of a
house.
We need your feedback! Please click
HERE to complete
a short survey.
| Convection is an important heat transfer process in a house. You probably find in your house that the heater is placed near the floor. There is a good reason for that arrangement. | |||
|
| A house can gain some heat from the sun through its windows. In winter, we want to maximize this gain. In summer, we want to minimize this gain. | |||
|
❹ Building your own 2D house: A design challenge
In this activity, you will draw a 2D house and simulate the energy flow in it.
The following are the instructions:
1. Adding a foundation.
Click "Rectangle" and drag the mouse in the window to draw a rectangle at the bottom.
2. Adding a wall.
Click "Rectangle" and drag the mouse in the window to draw a rectangle.
3. Adding a window.
Click "Rectangle" and drag the mouse in the window to draw a rectangle. Click "Select". Right-click on
the rectangle. Select "Properties" from the pop-up menu. When the "Properties" dialog shows up, set
"Absorption" to be 0 and "Transmission" to be 1 under "Optical properties".
4. Adding a roof.
You can add a rectangle to be a roof if you want to create a flat-top house. For any other shape,
click "Polygon" and draw a polygon. To make a reflective roof, click "Select" and then
right-click on the rectangle. Select "Properties" from the pop-up menu. When the "Properties" dialog
shows up, set both "Absorption" and "Transmission" to be 0 and "Reflection" to be 1 under "Optical properties"
5. Adding a ceiling.
The same as adding a rectangle.
6. Adding a heater.
Click "Rectangle", "Ellipse", or "Polygon" to add an object. Click "Select". Right-click on the object.
Select "Properties" from the pop-up menu. When the "Properties" dialog shows up, select "Constant temperature"
and set the temperature under "Source properties".
7. Others.
You can delete an object by clicking on it and pressing the DELETE key. You can change the properties of
any object by choosing the "Select" mode and right-click on it to access the "Properties" dialog. You
can also access the "Properties" of the entire system by right-clicking on an empty spot to invoke the
pop-up menu. You can add as many thermometers as you need by clicking on "Thermometer" and then clicking
within the window.
8. Save a screenshot of your work. To save a screenshot of your work on Windows,
press the "Print Screen" key on your keyboard and then paste it into the Paint program. Save the image as
a JPEG file and email it to your teacher!
Summary
This page covers a few topics in the heat engineering of a building. First, a building is a thermal system
that is constantly exchanging thermal energy with the environment and can be heated and cooled. Convection
plays an important role on heating and cooling in a house. Solar energy contributes to the heating of a
house.
We need your feedback! Please click
HERE to complete
a short survey.
| In this activity, you will draw a 2D house and simulate the energy flow in it. The following are the instructions: | |||||||
|
|||||||
|
This page covers a few topics in the heat engineering of a building. First, a building is a thermal system
that is constantly exchanging thermal energy with the environment and can be heated and cooled. Convection
plays an important role on heating and cooling in a house. Solar energy contributes to the heating of a
house.
We need your feedback! Please click HERE to complete a short survey. |