Sect 18.3

6 th Grade Science Chapter 18 Thermal Energy Notes Section 18.3 Chihuly at the New York Botanical Garden

What is heat engine?
A heat engine converts thermal energy into mechanical energy.
What is the Law of Conservation of Energy?
No device, including a heat engine, can produce or destroy energy.
Key Questions 1

A heat engine is a device that converts thermal energy into mechanical energy.
The engines used in cars, motorcycles, trucks, and other vehicles are heat engines.
Heat Engines

A steam engine is one of the earliest heat engines. A fire box heats steam. The steam drives a piston that is connected to a drive shaft. The drive shaft is connected to the wheels of the train.

What is an internal combustion engine?
Internal combustion engines burn fuel in a combustion chamber inside the engine.
What are some types of internal combustion engines?
Internal combustion engines include diesel engines, 2 stroke engines, and 4 stroke engines.
Key Questions 2 The Tadpole Galaxy

In internal combustion engines, the fuel burns in a combustion chamber inside the engine.
Internal Combustion Engines
Many machines, including cars, airplanes, buses, boats, trucks, and lawn mowers, use internal combustion engines.

Four cycle internal combustion engine

Two cycle internal combustion engine

What does a refrigerator do?
A refrigerator transfers the thermal energy from inside to outside the refrigerator.
What does the refrigerator coolant do?
The refrigerator coolant absorbs thermal energy from inside the refrigerator.
Key Questions 3 The Sombrero Galaxy

A refrigerator is a heat mover.
Refrigerators
It absorbs heat from the food and other materials inside the refrigerator.
Then it carries the heat to outside the refrigerator, where it is transferred to the surrounding air.

Liquid coolant is forced up a pipe toward the freezer unit.
Absorbing Heat
The liquid passes through an expansion valve where it changes into a gas.

When it changes into a gas, it becomes cold.
Absorbing Heat
The cold gas passes through pipes around the inside of the refrigerator.
Because the coolant gas is so cold, it absorbs heat from inside the refrigerator, and becomes warmer.

The heat absorbed by the coolant cannot be transferred to the air.
Releasing Heat
The warm coolant gas then passes through a compressor that compresses the gas.
When the gas is compressed, it becomes warmer than room temperature.

The gas then flows through the condenser coils, where it transfers heat to the cooler air in the room.
Releasing Heat
As the coolant gas cools, it changes into a liquid.
The liquid is pumped through the expansion valve, changes into a gas, and the cycle is repeated.

How does an air conditioner work?
Most air conditioners work in the same way that a refrigerator does.
What does a heat pump do?
A heat pump absorbs thermal energy from the air outside, and transfers it inside.
Key Questions 4

Opened in November 2005, the indoor resort features an 60-meter high indoor mountain with 5 slopes of varying steepness and difficulty, including a 400-metre-long run, the world's first indoor black run, and a 90-metre-long quarter pipe for snowboarders. A quad lift and a tow lift carry skiers and snowboarders up the mountain. Adjoining the slopes is a 3,000-square-metre Snow Park play area comprising sled and toboggan runs, an icy body slide, climbing towers, a snowball shooting gallery, an ice cave and a 3D theatre. Other attractions include a mirror maze and a snowman-making area. Winter clothing, ski and snowboard equipment are included.

A heat pump moves heat from one place to another.
Heat Pumps
In heating mode, the coolant absorbs heat through the outside coils.

Diagram the movement of coolant and the flow of heat when a heat pump is used to cool a building. Pg 537
Explain why diesel engines don’t use spark plugs.
Identify the source of thermal energy in an internal combustion engine.
Determine if you could cool a kitchen by keeping the refrigerator door open.
Describe how a refrigerator uses a coolant to keep the food compartment cool.
Questions Section 18.3

Sect 18.3

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