Using Heat Part 1

Science Journal Entry 31 Explain the 2 nd Law of Thermodynamics.

Heat Engines There are two types of heat engines. They are the external combustion engine and the internal combustion engine. An external heat engine burns fuel on the outside of the engine. Steam engines are external combustion engines. Invented by Thomas Newcomen in 1712, the first external heat engine was used to pump water out of coal mines. James Watt improved the engine and made it more efficient in There are two types of heat engines. They are the external combustion engine and the internal combustion engine. An external heat engine burns fuel on the outside of the engine. Steam engines are external combustion engines. Invented by Thomas Newcomen in 1712, the first external heat engine was used to pump water out of coal mines. James Watt improved the engine and made it more efficient in 1765.

The Steam Engine Steam locomotives were one of the most important uses of the steam engine. What makes their choo-choo sound? Steam locomotives were one of the most important uses of the steam engine. What makes their choo-choo sound?

Modern Steam Turbine Generator Most electric power plants today use steam turbines because they are very efficient. Most electric power plants today use steam turbines because they are very efficient.

How does a steam engine work? Steam enters one side first and then the other side. When steam comes into side one it is compressed by the piston within the cylinder. Then as it expands and cools it pushes the piston back to the other side and is expelled out of the exhaust. Steam enters one side first and then the other side. When steam comes into side one it is compressed by the piston within the cylinder. Then as it expands and cools it pushes the piston back to the other side and is expelled out of the exhaust.

Stream Engine Side Two When steam enters into side 2, it is compressed by the piston within the cylinder at the same time as the steam in side one is expanding, pushing the cylinder toward side two. Side 2 steam then expands and cools creating the compression in the opposite side and then the cooled steam is vented out into the air. When steam enters into side 2, it is compressed by the piston within the cylinder at the same time as the steam in side one is expanding, pushing the cylinder toward side two. Side 2 steam then expands and cools creating the compression in the opposite side and then the cooled steam is vented out into the air. es-equipment/steam1.htm es-equipment/steam1.htm

The Internal Combustion Engine The Internal Combustion Engine is a heat engine in which the fuel burns inside of the engine. Automobiles use this type of engine with gasoline as the fuel. The Internal Combustion Engine is a heat engine in which the fuel burns inside of the engine. Automobiles use this type of engine with gasoline as the fuel. In a four-stroke engine, a mixture of air and gasoline vapor enters the cylinder during the intake stroke. During the compression stroke, the piston compresses the gas mixture. At the end of the compression stroke, the spark plug is ignited starting the power stroke. In a four-stroke engine, a mixture of air and gasoline vapor enters the cylinder during the intake stroke. During the compression stroke, the piston compresses the gas mixture. At the end of the compression stroke, the spark plug is ignited starting the power stroke.

Power Stroke and Exhaust Stroke During the power stroke, the hot gas expands and drives the piston down. Then gas leaves the cylinder during the exhaust stroke and then the process starts all over again. During the power stroke, the hot gas expands and drives the piston down. Then gas leaves the cylinder during the exhaust stroke and then the process starts all over again. There are several of these cylinders all of which are going through this four stroke progression. This up and down (linear) motion of the pistons is converted into rotary motion by the crankshaft which is connected to the transmission which is connected to the drive shaft that is linked to the car’s wheels. There are several of these cylinders all of which are going through this four stroke progression. This up and down (linear) motion of the pistons is converted into rotary motion by the crankshaft which is connected to the transmission which is connected to the drive shaft that is linked to the car’s wheels.

Four Strokes Intake Stroke Intake Stroke Compression Stroke Compression Stroke Power Stroke Power Stroke Exhaust Stroke Exhaust Stroke 1:02 1:02 Animation for Four Stroke Engine Animation for Four Stroke Engine Animation for Four Stroke Engine Animation for Four Stroke Engine

Work and Waste Heat Only 1/3 of the fuel energy in a gasoline engine is converted to work. A car has a lot of waste heat that must be removed by the cooling system and transfer it from the engine to the environment. Only 1/3 of the fuel energy in a gasoline engine is converted to work. A car has a lot of waste heat that must be removed by the cooling system and transfer it from the engine to the environment. If this heat is not removed as designed, the engine would overheat and be destroyed by thermal expansion. A coolant usually water and antifreeze absorbs some thermal energy from the engine and passes it through the radiator. If this heat is not removed as designed, the engine would overheat and be destroyed by thermal expansion. A coolant usually water and antifreeze absorbs some thermal energy from the engine and passes it through the radiator. If your car is overheating, pull off of the road and turn off the car to allow it to cool down so that the engine is not harmed. If your car is overheating, pull off of the road and turn off the car to allow it to cool down so that the engine is not harmed

Wood-Burning Fireplaces Wood-burning fireplaces were the primary method of heating building. Before 1796 when Rumford designed a better fireplace, they lost a lot of heat through the chimney. They were smokey and not very efficient. Wood-burning fireplaces were the primary method of heating building. Before 1796 when Rumford designed a better fireplace, they lost a lot of heat through the chimney. They were smokey and not very efficient. Rumford’s fireplace was not as deep as the standard fireplaces of the time. He also slanted the walls of the fireplace to reflect heat into the room. Rumford’s fireplace was not as deep as the standard fireplaces of the time. He also slanted the walls of the fireplace to reflect heat into the room.

Fireplace Comparison

Central Heating Central Heating Systems heat many rooms from one central location. Central Heating Systems heat many rooms from one central location. Electrical energy, natural gas, oil, and coal are all fuels that are used for central heating. Electrical energy, natural gas, oil, and coal are all fuels that are used for central heating. Most heating systems use convection to distribute thermal energy. Most heating systems use convection to distribute thermal energy.

Hot-Water Heating A hot water heating system usually has a boiler, circulating pump, radiators, and a thermostat. A hot water heating system usually has a boiler, circulating pump, radiators, and a thermostat. First, the boiler heats the fuel. The fuel may be heating oil or natural gas. First, the boiler heats the fuel. The fuel may be heating oil or natural gas. Second, the burning fuel heats the water. The water is then carried to the radiators by the circulating pump. Second, the burning fuel heats the water. The water is then carried to the radiators by the circulating pump. Third, the hot water transfers its thermal energy to the radiator by conduction. The radiator will transfer energy to the air by conduction and by radiation. Third, the hot water transfers its thermal energy to the radiator by conduction. The radiator will transfer energy to the air by conduction and by radiation

Heating the Room Since hot air rises and the cool air sinks, this sets up a convection current in the room by which the entire room can be heated. The cooled water in the radiator returns to the boiler to start the process all over again. Since hot air rises and the cool air sinks, this sets up a convection current in the room by which the entire room can be heated. The cooled water in the radiator returns to the boiler to start the process all over again. A thermometer (a type of thermostat) consist of two metals, brass and steel wound up in a coil. The two metals expand at different rates causing the coil to rotate which trips a switch to turn off the heat. When the room cools the coil will rotate in the opposite direction flipping the switch to start heating again. A thermometer (a type of thermostat) consist of two metals, brass and steel wound up in a coil. The two metals expand at different rates causing the coil to rotate which trips a switch to turn off the heat. When the room cools the coil will rotate in the opposite direction flipping the switch to start heating again.

Hot-Water Heating System

Conclusion Steam Engines are external combustion engines. The 4-stroke engine in cars are internal combustion engines. Automobile engines release waste heat and must have a coolant to absorb it and keep the engine safe from destruction by thermal expansion. There are several types of machines that heat our homes. People use fireplaces, central heating, and hot- water heating systems. There are many other devices for heating and cooling that we will learn about in part 2.