Engines and Refrigerators

The first African American member of the American Society of Refrigeration Engineers was Frederick M. Jones. Jones invented a truck refrigeration system in 1939.

Describe Frederick M. Jones.

Due to the coolant gas being so cold, it absorbs thermal energy from inside the refrigerator and becomes warmer.

Describe how a refrigerator absorbs thermal energy.

The coolant gas flows through the condenser coils, where thermal energy is transferred to the cooler air in the room.

Describe how a refrigerator uses a coolant to keep the food compartment cool.

The shiny side reflects radiant heat better. If you want something to stay cool, wrap it with the shiny side out. If you want something to stay warm, wrap it with the shiny side down.

Describe the difference between the shiny side and the dull side of aluminum foil and its purpose.

Nikolaus August Otto invented the internal combustion engine in 1876. He is a German engineer.

Give information about Nikolaus August Otto.

Most cars have an engine with four or more combustion chambers or cylinders.

Most cars have what?

a. Chemical energy is stored in the chemical bonds between atoms. b. Radiant energy is the energy by electromagnetic waves. c. Nuclear energy is energy stored in the nuclei of atoms. d. Electrical energy is the energy carried by electrical charges as they move in a circuit.

Name and describe the four forms of energy besides mechanical energy.

The crankshaft turns the wheels of a car.

What does a crankshaft turn?

A refrigerator contains a material called a coolant that is pumped through pipes inside and outside the refrigerator. The coolant is the substance that carries thermal energy from the inside to the outside of the refrigerator.

What does a refrigerator contain and what is its purpose?

As the coolant gas cools, it changes into a liquid.

What happens as a coolant gas cools?

When a car converts thermal energy into mechanical energy, the car goes faster causing the car's kinetic energy to increase.

What happens when a car converts thermal energy into mechanical energy?

When a heat pump is used for cooling, it removes thermal energy from the indoor air and transfers it outdoors.

What happens when the heat pump is used for cooling?

A refrigerator is a heat mover.

What is a heat mover?

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

What is a heat pump?

Mechanical energy is the sum of the kinetic and potential energy of an object.

What is mechanical energy?

Many machines, such as lawnmowers, use internal combustion engines.

What uses them (internal combustion engines)?

The warmed coolant travels through pipes that are exposed to the outside air. Here the thermal energy is transferred to the outside air.

When is the thermal energy of an air conditioning unit to the outside air?

Nuclear energy is stored in the nuclei of atoms.

Where is nuclear energy stored?

In the internal combustion engines, the fuel burn in a combustion chamber inside the engine.

Write the definition of internal combustion engine.

In diesel engines, the air in the cylinder is compressed to such a high pressure that the highly flammable fuel ignites without the need for a spark plug.

Explain why diesel engines don't use spark plugs.

a. During the intake stroke, the piston inside the cylinder moves downward. As it does, air fills the cylinder through the intake valve, and a mist of fuel is injected into the cylinder. b. During the compression stroke, the piston moves up compressing the fuel-air mixture. c. At the top of the compression stroke, a spark ignites the fuel-air mixture. The hot gases that are produced expand, pushing the piston down and turning the crankshaft. d. The exhaust valve opens as the piston moves up, pushing the exhaust gases out of the cylinder.

Describe the four stroke cycle.

Each cylinder contains a piston that can move up and down.

Each cylinder contains what?

A heat engine is a device that converts thermal energy into mechanical energy.

Explain a heat engine.

According to the Law of Conservation of Energy, energy cannot be created or destroyed, it can only change forms when transformed from one form to another.

Explain the Law of Conservation of Energy.

The mixture of fuel and air is injected into a combustion chamber and ignited by a spark.

Explain what happens to a mixture of fuel and air.

It absorbs thermal energy from the food inside the refrigerator and then it carries the thermal energy to outside where it transferred to the surrounding air.

How does a refrigerator (heat mover) work?

When the fuel mixture is ignited, it burns explosively and pushes the piston down.

How does the burning of fuel mixture cause a piston to move?

The gas then flows through the condenser coils, where thermal energy is transferred to the cooler air in the room.

How is thermal energy released?

a. The first stroke is a combination of intake and compression. b. The second stroke is a combination of power and exhaust.

Many lawn mowers use a two stroke gasoline engine. Describe them both.