Heating Theory: Chapter 1
Introduction to Heating systems
In this module, we will discuss heating systems, their components, and how and why we use them. Skip to quiz!
History of Heating
The sun provides us with heat and light. However, when the sun goes down, we are faced with the cold, dark nighttime. Burning things to create heat and light is the oldest method of solving this problem known to mankind!
In 1,900,000 BC, humans began using wood fires to cook food and keep warm. In 2500 BC, Greeks in Ancient Rome developed central heating, providing heat to entire homes. This allowed people to get warm without having to sit directly next to the fireplace!
In AD 1883, Thomas Edison invented the electric heater, which did not require burning a substance for heat. In AD 1919, Alice Parker patented the first central heating system using natural gas as fuel. In AD 2000, “smart” technology allows us to control the heat in our homes using electronic devices.
The fuels we use to provide heat have changed over time. Wood was the first major fuel we used as a species, but today we rely more on oil and natural gas for fuel. For example, we used to cook food with wood-burning fires, but now our homes have natural gas stoves.
In time, we found new materials that could heat homes more efficiently. Efficient heating meant that we could produce more heat using less fuel. For example, to heat a house with firewood, we might need 3 kgs of wood. But with new fuels and materials, we would only need 1 kg of oil to heat the same house!
Modern Heating Systems
Old, primitive heating systems mainly relied on wood and coal as fuels. New, modern heating systems use fuels like natural gas, propane, and oil instead. For example, most of our fireplaces now burn natural gas or propane instead of firewood.
Recall that heating efficiency measures how much useful heat we get from the fuel we burn. Modern heating systems are much more efficient, meaning they use less fuel to get the same amount of heat! This also means they waste less fuel.
Burning primitive fuels like wood produces a lot of smoke. This smoke is bad for our lungs and bad for nature, as it releases particles that reduce our air quality. Newer fuels like natural gas burn more cleanly, creating less smoke. This makes them better for people and the planet!
Old heating systems required people to sit close to the heat source to receive its warmth. Modern central heating systems can carry heat throughout a home, so you do not need to be near the appliance. For example, you need to sit near a wood fire to feel its heat. Central heating, on the other hand, can distribute heat to your entire house.
Modern heating systems are more efficient than old ones, meaning they create more heat with less fuel. Modern heating systems produce less smoke and harmful gases than primitive ones, making them better for us and our environment. Modern heating systems can heat a whole house, whereas primitive ones could only heat a small area.
How Heating Systems Work
Combustion is simply the process of burning. Recall that a chemical reaction occurs when two chemicals mix. An example is the reaction of iron and oxygen creating rust on your bike! Combustion is a chemical reaction between oxygen in the air and fuel.
During combustion, a fuel heats up to high temperatures and reacts with oxygen in the air. This is called burning and produces heat and light in the form of a flame. Lighting a matchstick is an example of combustion. The friction of the match striking against the box causes the match to heat and react with oxygen, creating a flame.
Heating systems rely on heat produced by combustion. hen a fuel is heated and reacts with oxygen in the air, combustion occurs, and we create a flame that gives off heat and light. Heating systems use fans and pipes to circulate this hot air throughout our homes and keep us comfortable.
Humans rely on heating systems to cook food and keep warm. New fuels and materials have made our heating systems more efficient and better for both people and the planet over time. Heating systems rely on heat from combustion, a chemical reaction between oxygen and a heated fuel that creates a flame.
Concepts Review - Phase Changes
In this module, we will define the different phases of matter. We will also explore how changes in temperature or pressure can change these phases. Skip to quiz!
Phase Changes
Matter is any physical substance that takes up space. You are matter, the water you drink is matter, and the air you breathe is matter. Matter can exist in different forms, or states.
The three major states, or phases, of matter are:
Solid,
Liquid, and
Gas, which is also known as vapor.
Water can exist in every phase of matter! The solid form is ice, the liquid form is water, and the gas form is water vapor.
Atoms are the smallest building block of life. Each state of matter has a different atomic structure. Atoms in a solid are packed tightly, atoms in a liquid can roll around each other, and atoms in a gas can roam freely!
The phase of a substance depends on how fast its atoms are moving. We can change how fast atoms move by applying or removing heat. By changing the temperature or pressure of a substance, we can transfer heat and change the phase of the substance.
As the temperature of a substance increases, its atoms move faster and farther apart. If we increase the temperature enough, the atoms will move so fast that they change their structure and, the substance changes phase!
An example of temperature changing a phase is ice cream melting. The Sun heats the tightly packed atoms of the solid ice cream, causing them to move faster. As the atoms move faster, they break apart and move around each other. The solid ice cream then melts, becoming a liquid!
We can also change the state of a substance by applying or removing pressure. Pressure is the force we apply to an area of space. Adding pressure forces the atoms of a substance to move closer together and slower.
As mentioned in the video, increasing the pressure acting on a bubble changes the vapor to a liquid. Decreasing the pressure acting on the bubble changes the liquid to a vapor. This is because the increased pressure forces the atoms to move slower and closer together.
If enough heat or pressure is applied to a substance, it will change phases. The temperature at which a solid becomes a liquid is the melting point, and a liquid becomes a gas at the boiling point. The heat required to change phases depends on the substance. For example, water boils at 100℃, but kerosene oil boils at 40℃.
Whether a phase change happens because of a change in temperature or pressure, there is always a transfer of heat! If we boil a liquid by increasing the temperature, we are adding heat. If we turn a gas back into a liquid by adding pressure, we are removing heat.
The three phases of matter are solid, liquid, and gas. Phase changes occur when atoms move around as a result of the transfer of heat or pressure.
Concepts Review - Heat Transfer
In this module, we will discuss the different types of heat transfer. We will also explore the relationship between pressure, temperature, and heat. Skip to quiz!
Types of Heat Transfer
Recall that heat transfer is the movement of heat from one place to another. The types of heat transfer are:
Conduction,
Convection, and
Radiation
Conduction occurs when heat moves from one solid object to another through direct contact. These objects must have different temperatures. Just as waterfalls flow from high to low elevations, heat flows from high to low temperatures.
When we touch a hot coffee mug, heat moves from the mug to our hands because the coffee is warmer than our hands. This is an example of conduction. The heat flows from the hot coffee to our cold hands through the mug, a physical object.
Convection occurs when heat moves through liquids or gases. Recall heat moves from hot to cold. For example, if a room is on fire, convection occurs as the hot smoke from the room moves to the cold air in the rest of the house.
Boiling water relies on convection. The water at the bottom of the pot receives heat from the flame. This water warms up and rises to the top, where the water is cool. The water at the top becomes hotter, then moves back down to cool water at the bottom, and this cycle repeats.
Radiation transfers heat in rays or waves through the vacuum of space. A vacuum is the absence of matter. This means that, unlike conduction and convection, radiation can transfer heat without a solid, liquid, or gas medium.
The best example of radiation is the rays of Sun that heat the Earth. The Sun is millions of miles away, but we can still feel its heat because it travels through the vacuum of space in waves!
Heating systems burn fuels, heating the air around them. Through convection, this hot air rises to heat our homes. The cold air then settles, where it is heated again by the heating system. This cycle continues, heating our homes!
Heat Transfer Fundamentals
Recall that just as water flows from high to low elevations, heat flows from high to low temperatures. One example of heat flowing from hot to cold is your morning cup of coffee! As the cup sits, heat moves from the warm coffee to the cold air. This causes the air to heat up and the coffee to cool down.
Heat transfer happens everywhere! When you sit under the Sun, heat is being transferred to you by radiation. When you boil water for your tea, you are heating it using convection. And, when you accidentally grab the hot handle of the pot, you are feeling the effects of conduction!
Recall that heating systems typically rely on convection. Heating systems burn fuels, heating the air around them. Through convection, this hot air rises to heat our home, and the cold air settles, where it is then heated again. This cycle then repeats!
Pressure, Temperature, Heat
Pressure is the force applied to an area of space. Recall that an atom is the fundamental building block of life. When we increase the pressure on a substance in a closed container, we force the atoms to move closer together.
As we force these atoms closer together, they give up heat, and the temperature of the substance increases. Therefore, as the pressure applied to a liquid or gas increases, the temperature of this liquid or gas also increases.
If the temperature of a liquid increases, the amount of heat in the liquid also increases. Therefore, we can boil a liquid using less heat if we also apply pressure! We apply this principle in pressure cookers. The increased pressure allows us to cook at lower temperatures, requiring less fuel!
Boiler heating systems heat water in one place and supply that hot water throughout our homes or businesses. These systems keep water in a small area so that the pressure on it increases, causing the water temperature to increase. This means we need less fuel to heat water, so we can save money and the planet!
The main types of heat transfer are conduction, convection, and radiation. Our heating systems rely on convection. We can use the direct relation between pressure and temperature to heat liquids or gases by applying pressure to them.
Question #1: What new type of heating was discovered in the 1800s?
Electric heating
A central heating system using natural gas
Wood fires
None of the above
Scroll down for the answer...
Answer: Electric heating
Edison invented the electric heater in 1883.
Question #2: The main changes to our heating systems over time have been the types of fuel we burn and the materials we use to capture the resulting heat.
True
False
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Answer: True
The first fuel known to man was firewood, but today we rely more on new fuels like oil and natural gas.
The use of new materials, like stainless steel, has allowed us to capture heat from our fuels more efficiently.
Question #3: Modern heating systems are much more efficient than traditional ones, meaning they require less fuel to create the same amount of heat.
True
False
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Answer: True
Modern heating systems waste much less fuel in creating heat, making them more efficient than traditional heating systems.
Question #4: Which of the following is NOT a benefit of modern heating systems?
They are more efficient
They are less polluting
They can distribute heat evenly
They do not require fuel
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Answer: They do not require fuel
Modern heating systems are more efficient, less polluting, and can distribute heat more evenly than traditional ones.
However, most still require fuel to create heat.
Question #5: Combustion is the chemical reaction between oxygen and _______, producing heat and light in the form of a flame.
Hydrogen
A bike
A fuel
None of the above
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Answer: A fuel
Combustion is a chemical reaction between oxygen and fuel and produces heat and light in the form of a flame.
Question #6: If we decrease the pressure of a substance, its boiling point decreases.
True
False
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Answer: False
Heating systems use the heat from combustion to circulate hot air in our homes.
Question #7: Water cannot exist in every phase of matter.
True
False
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Answer: False
Water can exist in every phase of matter. The solid state is ice, the liquid state is water, and the gas state is water vapor.
Question #8: As the temperature of a substance increases, its atoms move ______ and farther apart.
Closer
Slower
Faster
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Answer: Faster
As the temperature of a substance increases, its atoms move faster and farther apart.
Question #9: We could change a solid into a liquid by increasing the:
Temperature
Pressure
Atoms
a & b
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Answer: Temperature
The state that a substance is in depends on both its temperature and pressure. Increasing the temperature could turn a solid into a liquid. However, increasing the pressure would turn a liquid into a solid.
Question #10: No matter what, phase changes require a transfer of _______.
Fuel
Pressure
Temperature
Heat
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Answer: Heat
Whether a phase change happens because of a change in temperature or pressure, there is always a transfer of heat!
Question #11: What is the main difference between conduction and convection?
There is no difference.
Convection takes place at higher temperatures than conduction.
Heat moves in the opposite direction for each.
Convection travels through liquids or gases, while conduction travels through solid matter.
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Answer: Convection travels through liquids or gases, while conduction travels through solid matter.
Conduction occurs when heat moves from one solid object to another through direct contact.
Convection occurs when heat moves through liquids or gases.
Question #12: Which method of heat transfer does not need matter to transfer heat?
Radiation
Convection
Conduction
None of the above
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Answer: Radiation
Radiation transfers heat through rays or waves and does not need a material medium.
Question #13: Heating systems typically rely on:
Radiation
Convection
Conduction
None of the above
Scroll down for the answer...
Answer: Convection
Heating systems use convection. As hot air rises to heat our home, the cold air settles, where it is then heated again, and the cycle continues.
Question #14: Boiler heating systems require less fuel because they use pressure to increase the temperature of the liquid.
True
False
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Answer: True
As we increase the pressure on a liquid, the temperature increases, and so does the heat in the liquid. Therefore, we do not need as much fuel to heat up the liquid if it is at a higher pressure.