Chapter 6 Section 3

Heating Systems Forced air– most common type of heating system. It uses a furnace to burn a fuel . A fan then blows the air through large ducts which lead to vents in each room. Cool air returns to the furnace via the vents as well.

Radiator System– a closed metal container that contains hot water or steam. The thermal energy of the hot water or steam transferred through the metal to the surrounding air. The air would then move through the room by convection currents.

Electric heating system—electrically heated coils placed in floors and walls heat the surrounding air by conduction.

Solar Heating Passive Solar Heating—materials inside buildings absorb radiant energy from the sun during the day to heat up. An example would be a green house.

Active Solar Heating—uses solar collectors to absorb radiant energy from the sun. These are more commonly know as solar panels. These panels will store the energy and use it to heat things like pipes filled with water to flow around the house to heat the house at night.

Thermodynamics Thermodynamics is the study of the relationship of how thermal heat, energy, and work are related. Heat and work increase thermal energy. There are two laws of thermodynamics.

The First Law of Thermaldynamics The increase in thermal energy of a system is equal to the work done on the system plus the heat transferred to the system. Open system—energy levels can change Closed system—energy levels remain the same

Second Law of Thermodynamics It is impossible for heat to flow from a cold object to a warm object unless work is added. It also states that heat cannot be completely transformed into work. It is this law that is the foundation for things like air conditioners and refrigerators.

Converting Heat to Work A heat engine is a devise that converts heat into work. An example would be a car engine. It converts the chem. Energy of gas into thermal energy. It then converts some of the thermal energy into work by rotating the car’s wheels. Only about 25% of the thermal energy is converted to work.

Internal combustion engine An engine in which fuel is burned inside the engine in chambers or cylinders. An example of this would be a car engine.

1. intake—the intake valve opens as the piston moves downward, drawing a mixture of gas and air into the cylinder. 2. compression—the intake valve closes as the piston moves upward, compressing the fuel-air mixture. 3. power—a spark plug ignites the fuel-air mix. As the mix burns, hot gases expand, pushing the piston down. 4. exhaust—as the piston moves up, the exhaust valve opens, and the hot gases are pushed out of the cylinder

Heat Movers Refrigerator—moves heat by doing work on the coolant Air conditioner—similar to a refrigerator, but instead of just dumping the warm air out, it brings it back to the coolant to cool off so the cycle can continue. Heat pump—a two-way heat mover. In warm weather it acts like an air conditioner, sucking warm air out of the house. In cool weather it functions in the opposite way.

Human Coolant You naturally produce your own coolant: sweat. Sweat forms on the outside of the skin to allow for evaporative cooling. This carries away the heat from your body.

Section Check How does heat flow from a warm to a cool object satisfy the first law of thermodynamics? Why can’t heat be converted completely into work? How does a refrigerator work on a coolant? How does thermal energy differ in a closed system vs an open system?