The refrigeration cycle is right at the heart of every air conditioner, heat pump, or refrigeration-based HVAC system. It might be a relatively simple process (albeit based on some complex physics), but it’s a vital one and highly effective at its job. Essentially, it moves heat from one place to another and thanks to this process your indoor spaces can be cooled in the summer (and in some systems, warmed up in winter.)
Because it’s such a critical process, it’s important for homeowners and business owners to really understand how exactly the HVAC refrigeration cycle works. Once you’re informed, you will be better placed to know when it’s time for maintenance as well how to look out for common faults. This is key, because a fault could affect both your comfort and your energy bill. This is why, when a technician or a facility manager works on an HVAC system, the refrigeration cycle is one of the first things they will look at during troubleshooting.
At Daikin, we have been pioneering HVAC solutions for over a century and today employ more than 100,000 people worldwide, all focused on delivering high-performance systems for residential, commercial, and industrial spaces. In this article, we will look at how the HVAC refrigeration cycle works and we will break down the key components of that cycle as well as the role each piece plays in the overall process. We will also examine how optimising the refrigeration cycle can improve your system’s performance. So let’s get started.
How the HVAC refrigeration cycle works
One clarification that needs to be made early on is that the refrigeration cycle does not actually make cold air. What it does is remove heat from a specific area and then release it in another area. It does this by moving a refrigerant through a closed loop where it changes between liquid and gas.
In cooling mode, the HVAC system absorbs heat from indoor air and then sends it outside. In heating mode, it reverses this process, bringing heat inside. The cycle runs non-stop while the system is operating.
The four main components of the refrigeration cycle
HVAC systems can vary quite a lot in terms of size and how they are configured. But regardless of those factors, the refrigeration cycle uses four core components. Let’s look at these now:
Compressor: This is the key component because it compresses low-pressure refrigerant vapour and increases its pressure and temperature. The refrigerant is then ready to release heat in the next stage of the cycle.
Condenser: This allows the high-pressure refrigerant gas to release heat to the surrounding air. As heat is sent out, the refrigerant condenses into a high-pressure liquid.
Expansion device: This is usually an expansion valve or metering device that controls how much refrigerant can enter the evaporator. As the liquid refrigerant passes through this component, its pressure drops which causes it to cool.
Evaporator: This is where heat absorption happens. The now cold, low-pressure refrigerant absorbs heat from indoor air, making the refrigerant evaporate. This heat removal cools the air down before circulating it back into the space. Once the refrigerant leaves the evaporator, it returns to the compressor and the cycle begins once again.
Step-by-step breakdown of the refrigeration cycle
Let’s now look at how these different components work together, each as part of a wider process:
Step 1: Heat absorption in the evaporator
First, warm indoor air is blown over the evaporator coil. Then refrigerant inside the coil absorbs the heat from the air and evaporates from a liquid into a gas. The air is now cooler and also dehumidified. The air is now ready to be pumped back into the room.
Step 2: Compression
The low-pressure refrigerant gas enters the compressor where its pressure and temperature is raised and it transforms into a hot, high-energy vapour.
Step 3: Heat removal
The hot refrigerant flows into the condenser coil. Outdoor air passes over the coil, carrying heat away from the refrigerant. As it loses heat, the refrigerant condenses back into a liquid.
Step 4: Pressure reduction
The high-pressure liquid refrigerant passes through the expansion device. The sudden pressure drop cools the refrigerant, preparing it to absorb heat again in the evaporator.
Why the refrigeration cycle is critical for HVAC efficiency
How effective your HVAC system will be depends a great deal on the refrigeration cycle and how well it is operating. Making small improvements in performance of the individual components, and each part of the process, can really help reduce your energy bills.
When everything is working well, you should be seeing faster temperature stabilisation. You will also notice you are using less electricity and the wear and tear on components is also much less – meaning your system should last longer. And of course your indoor environment is much more comfortable.
Generally, problems can occur when coils get dirty or the compressors fail. These can force the system to work harder which in turn means higher energy bills. It will also mean your equipment won’t last as long.
When you purchase a modern high-quality HVAC system by Daikin you have the peace of mind knowing that each stage of this important cycle has been refined to maximise performance under different loads and climate conditions.
FAQs about the HVAC refrigeration cycle
What happens if one part of the refrigeration cycle fails?
If any component fails then it will affect the entire cycle. If a compressor is faulty then it can completely stop refrigerant circulation. Meanwhile, if an expansion valve is blocked it can reduce the cooling capacity. Then there are minor issues like dirty condenser coils which can also impact heat transfer and reduce the efficiency of your HVAC system.
Does the refrigeration cycle work differently in heat pumps?
The basic cycle is the same but heat pumps include a reversing valve that changes the direction of refrigerant flow. This means the system can absorb heat from outside air and release it indoors.
What type of refrigerant is used in modern HVAC systems?
Modern systems use refrigerants to balance performance with environmental impact. Common examples include R-410A and newer alternatives such as R-32 which are more environmentally-friendly. Regulations increasingly favour refrigerants with lower environmental footprints.
Can refrigerant leaks affect cooling performance?
Yes. Refrigerant leaks disrupt the refrigeration cycle and reduce heat absorption and transfer. This leads to poor cooling and your system using more energy consumption – as well as potential damage to the compressor.
About Daikin
Daikin is a global leader in HVAC innovation, with decades of expertise in refrigeration technology and system design. Our company focuses on engineering solutions that optimise every stage of the refrigeration cycle to deliver the best possible indoor comfort across residential, commercial and industrial settings.
By continually refining how heat is absorbed, transferred, and released, Daikin systems deliver superior energy efficiency and long-term performance. This commitment to innovation helps homeowners and businesses keep their indoor environments comfortable while reducing costs and environmental impact.
