ClassX Video Lessons Youtube Channel The Engineering Mindset Air Conditioning System Basics hvacr how does it work
Air conditioning systems are fascinating pieces of technology that keep our indoor environments comfortable. At the heart of these systems are four main components: the compressor, the condenser, the expansion valve, and the evaporator. Let’s explore how these components work together to cool your space.
In a typical air conditioning system, the compressor circulates a special fluid known as refrigerant through a network of pipes connecting all the components. The condenser and the evaporator are both heat exchangers, with the condenser located outside the building and the evaporator inside the room being cooled. The expansion valve plays a crucial role in regulating the flow of refrigerant throughout the system.
Refrigerant is a specially designed fluid that can easily transition between liquid and gas states due to its low boiling point. For instance, refrigerant R410A boils at -48 degrees Celsius (-55 degrees Fahrenheit), although this boiling point can vary with pressure. When the refrigerant is in a room at 30 degrees Celsius (86 degrees Fahrenheit), it boils and turns into vapor, absorbing heat from the surrounding air.
As the refrigerant enters the evaporator, it is a low-pressure, low-temperature liquid-vapor mixture. A fan blows the room’s ambient air over the evaporator’s pipes, causing the refrigerant to boil and absorb heat from the air. This process cools the air, which exits the evaporator at a lower temperature. The refrigerant continues to absorb heat until it becomes a slightly superheated vapor, ensuring no liquid droplets reach the compressor, which could cause damage.
The compressor draws in the low-pressure, low-temperature vapor from the evaporator and compresses it into a smaller space, increasing its pressure and temperature. This process is similar to how a bicycle pump heats up when compressing air. The compressed refrigerant, now a high-pressure, high-temperature vapor, is pushed into the condenser.
Located outside, the condenser allows the refrigerant to release its absorbed heat. A fan blows ambient air over the condenser, facilitating heat transfer from the refrigerant to the outside air. As the refrigerant cools, it condenses back into a liquid, similar to how steam condenses on a cold window. The refrigerant exits the condenser as a high-pressure, medium-temperature liquid and moves to the expansion valve.
The expansion valve controls the amount of refrigerant entering the evaporator, ensuring optimal cooling and system efficiency. It creates a pressure difference by allowing refrigerant to pass through a small opening, causing it to expand and cool as it enters the evaporator. This process is akin to how a spray can cools when used.
Initially, fixed orifice devices were used to control refrigerant flow, but they lacked precision. The thermostatic expansion valve improved this by sensing superheat levels and adjusting accordingly. However, it required manual adjustments and was prone to errors. The latest advancement is the electronic expansion valve, which automatically adjusts in real-time for optimal performance and efficiency.
Understanding these components and their functions provides insight into how air conditioning systems maintain comfortable indoor environments. For more information on HVAC and refrigeration engineering, explore additional resources and continue your learning journey.
Create a detailed diagram of an air conditioning system using digital tools like Lucidchart or Canva. Label each component: compressor, condenser, expansion valve, and evaporator. Include arrows to show the flow of refrigerant and annotate the diagram with brief descriptions of each component’s function. This will help you visualize the system’s operation and reinforce your understanding of how each part contributes to cooling.
Conduct a virtual lab experiment to explore the properties of refrigerants, focusing on their boiling points and phase changes. Use simulation software to observe how refrigerants like R410A behave under different pressures and temperatures. Document your findings and discuss how these properties are critical to the functioning of an air conditioning system.
Analyze a case study of a real-world air conditioning system failure. Identify which component failed (compressor, condenser, expansion valve, or evaporator) and hypothesize the cause based on your understanding of the system. Present your analysis in a report, including potential solutions and preventive measures to avoid similar issues in the future.
Participate in a group discussion about the evolution of expansion valves, from fixed orifice devices to electronic expansion valves. Debate the advantages and disadvantages of each type, and consider how technological advancements have improved system efficiency and performance. Share your insights and learn from your peers’ perspectives.
Build a simple model of an air conditioning system using household materials. Use a small fan, a coil of copper tubing, and a container of ice water to simulate the evaporator and condenser processes. Document the steps and results, and explain how your model demonstrates the basic principles of air conditioning. This hands-on activity will solidify your understanding of the system’s mechanics.
Here’s a sanitized version of the provided YouTube transcript:
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Sponsored by Danfoss.
When we look at an atypical refrigeration system, we have the compressor, the condenser, the expansion valve, and the evaporator. The condenser and the evaporator are both heat exchangers. The condenser sits outside the property, and the evaporator sits inside the room being cooled. The compressor circulates a refrigerant in the pipework, cycling between all of these components. The expansion valve regulates the flow of refrigerant.
The refrigerant is a specially designed fluid that can easily change between being a liquid and a gas due to its low boiling point. For example, refrigerant R410A will boil at -48 degrees Celsius or -55 degrees Fahrenheit, although this can change with pressure. If the refrigerant is inside a pipe within a room at 30 degrees Celsius (86 degrees Fahrenheit), this is sufficient to cause it to boil from a liquid into a vapor.
By the way, if you want some refrigerant charts, you can download these for free from our website; I’ll link to these in the video description below.
The refrigerant enters the evaporator as a low-pressure, low-temperature liquid-vapor mixture. It flows inside the pipe while a fan moves the ambient air of the room over the outside of the pipe. This causes the refrigerant to boil, absorbing heat from the air through the pipe wall, and then it evaporates. As the refrigerant evaporates, it carries away the heat, similar to how boiling water turns into steam and carries heat away. The air outside enters hot and leaves cold.
The refrigerant continues to travel through the evaporator, picking up more heat until it becomes slightly superheated, meaning it is now completely gas and contains no liquid droplets. Liquid refrigerant can damage the compressor, so we want to ensure it doesn’t reach the compressor.
The compressor sucks in the refrigerant leaving the evaporator as a low-pressure, low-temperature, slightly superheated vapor. It then compresses this vapor into a much smaller space, increasing the pressure. All the heat picked up in the evaporator is now contained in a smaller volume, causing the temperature to rise. This is important, and we will see why shortly. If you’ve ever pumped up a bicycle tire, you may have noticed the pump gets hotter as it compresses the air.
The refrigerant is then pushed into the condenser, entering as a high-pressure, high-temperature superheated vapor. The condenser is located outside, and on a warm summer day, the outside air might be very warm. Heat always flows from hot to cold, so we need to ensure that the refrigerant is hotter than the outside air; otherwise, the unwanted heat cannot leave the refrigerant and the system. A fan helps blow ambient air over the condenser to remove this heat.
As the heat is removed by the air, the refrigerant condenses back into a liquid. This is similar to steam condensing on a cold window; the cold surface causes the steam to turn back into liquid, which then runs down the window. The refrigerant exits as a high-pressure, medium-temperature saturated liquid and heads to the expansion valve.
The expansion valve regulates the amount of refrigerant entering the evaporator to control the superheat. If it allows too much refrigerant to flow, it can flood the evaporator, preventing the refrigerant from evaporating and potentially damaging the compressor. Conversely, if it lets in too little refrigerant, the system won’t provide enough cooling and will operate inefficiently.
The expansion valve regulates the refrigerant by allowing it to pass through a small hole, creating a large pressure difference across the valve. One side is high-pressure liquid, while the other side is almost empty. The small hole causes the refrigerant to spray into the evaporator as a part liquid, part vapor mixture. The refrigerant expands to fill the empty space on the other side, causing a drop in pressure and temperature.
This is similar to spraying a deodorant or spray paint can; as it flows through a small hole, it expands into a part vapor and part liquid mixture, and the can becomes cooler.
Originally, this was controlled using a fixed orifice device, which you might still find in some refrigerators. The hole within this device was a fixed size, so the entire system would turn on and off to meet cooling demand. While it works, it doesn’t maintain stable temperature control because the system simply cycles on and off.
The next evolution was the thermostatic expansion valve, which is still widely used today. It senses the superheat at the outlet through a bulb filled with another refrigerant. This refrigerant expands to close the valve when the superheat is too high and condenses to open the valve when the superheat is too low. This type of valve needs to be manually calculated and adjusted by a technician. While it works well, it is prone to mistakes, takes time to set up, and is only adjusted once per service visit, which is not ideal for peak performance.
The latest evolution is the electronic expansion valve, which uses a controller to measure the exact temperature and pressure, adjusting the valve position automatically in real-time for optimal performance and maximum system efficiency.
That’s it for this video! To continue learning about HVAC and refrigeration engineering, click on one of the videos on screen now, and I’ll catch you there for the next lesson. Don’t forget to follow us on Facebook, Twitter, LinkedIn, Instagram, and at TheEngineeringMindset.com.
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This version removes any informal language and maintains a professional tone while conveying the same information.
Air Conditioning – A system or process for controlling the temperature, humidity, and sometimes the purity of the air in an interior space. – The air conditioning system in the laboratory ensures that the equipment operates within the optimal temperature range.
Refrigerant – A substance used in a heat cycle, typically including a reversible phase change, to transfer heat from one area and remove it to another. – The choice of refrigerant can significantly impact the efficiency and environmental footprint of an air conditioning system.
Compressor – A mechanical device that increases the pressure of a gas by reducing its volume, commonly used in refrigeration and air conditioning systems. – The compressor is a critical component in the refrigeration cycle, as it compresses the refrigerant and circulates it through the system.
Condenser – A device or unit used to condense a gaseous substance into a liquid state through cooling, often used in refrigeration systems. – The condenser in the air conditioning unit releases heat to the outside environment, allowing the refrigerant to cool and liquefy.
Evaporator – A component in a refrigeration system where the refrigerant absorbs heat and evaporates, cooling the surrounding environment. – The evaporator coil in the air conditioning system absorbs heat from the indoor air, providing a cooling effect.
Expansion Valve – A device in a refrigeration system that reduces the pressure of the refrigerant, allowing it to expand and cool before entering the evaporator. – The expansion valve regulates the flow of refrigerant into the evaporator, ensuring efficient cooling performance.
Heat – A form of energy associated with the movement of atoms and molecules in a substance, often transferred between systems or objects. – In thermodynamics, heat transfer is a fundamental concept that describes how energy moves from one system to another.
Temperature – A measure of the average kinetic energy of the particles in a system, indicating how hot or cold the system is. – Engineers must carefully monitor the temperature of materials during manufacturing processes to ensure product quality.
Pressure – The force exerted per unit area on the surface of an object, often measured in pascals or atmospheres. – Understanding the pressure changes in a fluid system is crucial for designing efficient pumps and compressors.
Efficiency – A measure of how well a system converts input energy into useful output, often expressed as a percentage. – Improving the efficiency of thermal systems can lead to significant energy savings and reduced environmental impact.
