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Behind the Chill: Understanding Refrigeration

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Refrigeration is an essential, often taken for granted, part of modern life. Whether at a massive industrial scale or in a household kitchen anyone could tell you the importance of refrigeration in their lives, or at least, how much pain life becomes when their home refrigerator goes on the fritz.

No matter the size, from a compact household refrigerator to a large industrial cooling system, all refrigeration systems rely on the same core components. In this blog, we will break down those key components and explain how each one contributes to the greater cooling process.

Understanding Heat Transfer

At its core, refrigeration is a process meant to remove heat from one area and expel it into another. Think of this like a sponge moving water from a bucket into a sink. If you put a sponge into a bucket full of water, the sponge will absorb some of the water and expand. If you were to then move the sponge to the sink and squeeze, the pressure of your hand would force the water out of the sponge.

Refrigeration works the exact same way. The refrigerant inside of a refrigeration system absorbs the heat when depressurized and expels heat when pressurized. By continuously pressurizing in one location and depressurizing in another, the refrigeration system can remove a significant amount of heat from an area, creating a cooled environment within an insulated space.

The Cooling Loop

Of course, heat transfer is far more complex than a sponge. Refrigeration requires many different components working together to control the refrigerant’s absorption and release of heat. This controlling process is called the Cooling Loop.

The cooling loop is made up of four primary components: the compressor, the condenser, the evaporator, and the expansion valve.

The Evaporator

The evaporator is designed to remove heat from the refrigerator’s insulated enclosure. It does this by using fans to direct hot air over coils filled with liquid refrigerant. The refrigerant is in a very depressurized state, maximizing the refrigerant’s ability to absorb heat and reducing its boiling point. Even the cold air of the insulated enclosure will cause the refrigerant to boil into vapor, drawing in even more heat in the process.

The Compressor

The compressor is the stage of the cooling loop after the evaporator. Its primary goal is to compress the low-pressure vapor from the evaporator into a high-pressure vapor. Just like how depressurizing the liquid refrigerant made it want to become vapor and absorb heat, pressurizing the vapor refrigerant makes it want to condensate into a liquid and expel heat. However, insulated piping still traps the refrigerant and prevents it from expelling its heat. Thus, the vapor refrigerant becomes extremely high-pressure, and very high temperature.

The Condenser

The condenser is the opposite of the evaporator, designed to dump the heat stored in the vapor refrigerant into the atmosphere. The primary two styles of condensers are water-cooled condensers and air-cooled condensers. In an air-cooled condenser, fans are set up to blow across the condenser coils. In a water-cooled condenser, the refrigerant expels its heat into a water system. The water system then cycles its trapped heat through a cooling tower to evaporate into the atmosphere. Both styles of condenser allow the high-pressure refrigerant to expel its pent-up heat into the air and return to a liquid state.

The Expansion Valve

The expansion valve is the opposite of the compressor. The valve controls the pressure of the liquid refrigerant by reducing how much refrigerant can flow past it. This restriction causes the liquid refrigerant to remain very high-pressure on the condenser side of the valve, but low pressure on the evaporator side of the valve. As refrigerant flows through the valve, the sudden drop in pressure causes the refrigerant to rapidly lose temperature, which in turn prepares the liquid for the evaporator, restarting the cooling loop.

The Refrigerants

The refrigerant is the single most important component of the refrigeration system. Not just any fluid can be a refrigerant. It needs to have a low boiling point but be stable, manageable, and easily manufactured. Additionally, recent regulations have been slowly restricting the most climate-damaging refrigerants. Shown below are the most common forms of refrigerants.

Carbon Dioxide

Carbon Dioxide, known as R744 in the refrigeration industry, is a natural refrigerant with low global warming potential. CO2 systems require very high pressure to operate efficiently but are very effective for large to medium-scale applications.

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Propane

Propane, also known as R290, is a natural refrigerant that is common in self-contained refrigerators and is very energy efficient. Because propane is flammable, use of this refrigerant is restricted to small applications.

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Ammonia

Ammonia, also known as R717, is a natural refrigerant that is highly effective in industrial applications. However, it is also toxic and requires strict safety standards and mitigation technologies.

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Hydrofluorocarbons (HFC)

Hydrofluorocarbons are a class of refrigerants that are widely used by nearly every HVAC and refrigeration application. HFCs have been the most common refrigerants for decades, but recent climate regulations have been slowly phasing them out due to their high global warming potential.

Hydrofluoroolefins (HFO)

Hydrofluoroolefins are a class of refrigerants designed as a non-natural alternative to HFC refrigerants. A sub-class of HFO refrigerants called A2L refrigerants are becoming a popular option for refrigeration systems due to their low global warming potential.

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Want to Learn More?

Refrigeration systems vary widely in size and application, but the principles covered in this blog are the fundamental cooling processes used in countless applications across the world. If you want to learn more, Zero Zone’s blog posts on the latest updates and information in the refrigeration industry is a great place to start.

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