Sect 18.3

6th Grade Science

Chapter 18 Thermal Energy

Notes Section

18.3Chihuly 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.

1. Diagram the movement of coolant and the flow of heat when a heat pump is used to cool a building. Pg 537

2. Explain why diesel engines don’t use spark plugs. 3. Identify the source of thermal energy in an internal

combustion engine.4. Determine if you could cool a kitchen by keeping the

refrigerator door open.5. Describe how a refrigerator uses a coolant to keep the food

compartment cool.

Questions Section 18.3