How does an evaporator work in AC and refrigeration? Types, Components, and Functions Explained

Published: 05 May 2025

How does your fridge keep food cold, or how does your AC cool the room on a hot day? It all starts with one small but powerful part: the evaporator. This little hero doesn’t just chill the air—it pulls heat away from the space you want to keep cool.

In this guide, I’ll walk you through what an evaporator is, how it works, where it’s used, and why it matters. Don’t worry—I’ll keep it simple, clear, and with real-life examples. Ready to learn how it happens? Let’s jump in.

Table of Content

What Is an Evaporator?

An evaporator is a part of a cooling cycle that removes heat from the air. It resembles a set of cold metal coils, usually copper or aluminum. Inside those coils is a cold liquid called refrigerant.

An evaporator is a part of a cooling system that removes heat from the air. It looks like a set of cold metal coils—usually made of copper or aluminum. Inside those coils flows a cold liquid called refrigerant. When warm air from a room or fridge passes over the coils, the refrigerant absorbs the heat, causing the air to become cooler. It might seem like magic, but it’s just innovative science.

Where is the Evaporator Located?

Evaporators are found in many types of systems. In a home air conditioner, they’re placed near the air handler or tucked inside the indoor unit. The evaporator sits inside the cooled space in commercial refrigerators or freezers, often in the back or on top. In chillers or large industrial setups, the evaporator connects to water or air ducts as part of a much bigger cooling system.

How Does an Evaporator Work?

An evaporator works by removing heat from the surrounding air or fluid. It’s not making cold—it’s taking the heat away. The magic happens inside its metal coils, which are filled with a cold substance called refrigerant.

When warm air passes over these coils, the refrigerant absorbs the heat. As it collects heat, it begins to boil and turn into gas. This is called evaporation, and it’s how the evaporator cools the air around it.

Once the refrigerant becomes a gas, it moves out of the evaporator and goes to the compressor, where the cooling cycle continues. This step-by-step process keeps your space cool, your fridge cold, and your system running smoothly.

What are The Key Functions of an Evaporator

The evaporator does more than sit there—it plays an active role in the cooling process. Its job is to remove heat, turn liquid into gas, and keep the system running smoothly.

First, an evaporator’s primary function is to absorb heat. Warm air flows over the cold coils, and the refrigerant inside soaks up that heat, making the surrounding air cooler.

Next, the evaporator helps change the refrigerant from a liquid to a gas. This process is essential because only gas can move to the compressor for the next step in the cooling cycle.

Lastly, it helps control pressure and temperature inside the system. Lowering the pressure in the coils allows the refrigerant to evaporate at the right temperature, keeping everything balanced and efficient.

What are The Key Components of an Evaporator Coil?

An evaporator coil may look simple, but it’s built with several parts that work together to keep things cool. Let me explain each one in plain words.

1. Coils (Tubes)

These are the metal pipes where the refrigerant flows. They’re usually made of copper or aluminum. The coils carry the cold liquid that soaks up heat from the air.

2. Fins

Thin metal fins are attached to the outside of the coils. They help spread the cold across a bigger area so the coil can absorb more heat faster. Think of fins as tiny wings that allow the coil to perform better.

3. Distributor Assembly

This part helps spread the refrigerant evenly into the coil’s different tubes. Without it, some tubes might get more refrigerant than others, making the system work unevenly.

4. Leads (Small Tubes)

Leads are the little pipes connected to the distributor. They guide the refrigerant into different coil parts, helping everything stay balanced and calm.

5. A-Frame Shape (Optional)

In home air conditioners, the coil is sometimes bent into a shape like the letter “A”. This saves space and gives more surface area to cool the air faster.

What are The Types of Evaporators

Not all evaporators are the same. Different systems need different types depending on how much cooling they need, how often they run, and the space they’re used in. Let’s look at the main types in simple terms.

1. Direct Expansion (DX) Evaporator

This is the most common type. It’s found in home air conditioners and small cooling units. The refrigerant flows through the coil, picks up heat, and turns into a gas inside the unit.

2. Flooded Evaporator

This one is used in big systems like chillers or factories. It constantly fills the coil with refrigerant, absorbing lots of heat without stopping. It’s strong and steady, but it needs more parts to control it.

3. Plate Evaporator

This type is flat and smooth, often used in fridges or freezers. It doesn’t have fins, and it works well in small spaces. It’s simple and easy to clean.

4. Shell and Tube Evaporator

Found in industrial systems, this one uses a big shell filled with refrigerant and small tubes carrying water or another fluid. The refrigerant cools the liquid inside the tubes, which then gets used to chill air or equipment.

5. Static Evaporator

This one doesn’t use a fan. It just slowly cools the space around it. You’ll see these in small fridges or chest freezers.

6. Film and Diffusion Evaporators

These are used in special systems like food factories or chemical plants. They spread the refrigerant in thin layers or mix air and liquid for better cooling.

Where are these used?

Homes → DX evaporators
Factories → Shell and Tube, Flooded.
Supermarkets → Plate evaporators
Labs or special equipment → Film and Diffusion types

Design Choices That Affect Performance

The way an evaporator is designed can affect its performance. A few smart design choices can make your system run better, last longer, and use less energy. Let me explain.

1. Fin Spacing

Fins help the coil absorb heat, but if they’re packed too tightly, moisture from the air can freeze on them. That frost blocks airflow and slows everything down. Wider fin spacing helps prevent icing in cold places.

2. Circuit Layout

Inside the coil, the refrigerant travels through small tubes called circuits. If all the circuits are the same length and shape, the refrigerant flows evenly, resulting in smoother cooling with no hot or cold spots.

3. Distributor Nozzle Size

This tiny opening controls how fast the refrigerant enters the coil. If it’s too small, the system can’t move enough refrigerant. If it’s too big, it can flood the coil and lower efficiency. Getting this size right is a big deal.

4. Drainability

Oil can build up inside the coil in systems with low refrigerant speed. That oil can block the flow. So, designers sometimes tilt the coil or build in drain points to help the oil flow out easily.

5. Coil Shape

Some systems use a coil shaped like the letter “A” to fit in tight spaces while giving lots of surface area. This A-frame shape helps cool more air at once without needing extra room.

Smart design means better cooling, lower energy bills, and fewer breakdowns. Even small details, like the thickness of the metal or the length of the tubes, can make a big difference.

Conclusion

The evaporator may be a quiet part of your cooling system, but it does the heavy lifting—pulling heat out and keeping things cool. Its job stays the same whether in your home AC, a supermarket fridge, or a factory chiller. Now that you know how it works and what can go wrong, you’re better prepared to take care of it. Want your system to run better and last longer? Start by keeping the evaporator clean and working right.

Why is my evaporator coil freezing up?

If your coil is covered in ice, it’s usually because of low airflow or refrigerant levels. A dirty air filter, blocked vent, or fan issue can cause poor airflow. Low refrigerant can also make the coil too cold. If this problem persists, turn off the system, check the filter, and call a technician.

How often should evaporator coils be cleaned?

At least once a year is a good rule. If your system runs often or you’re in a dusty area, clean it every 6 months. Dirty coils make the system work harder, which can raise your energy bill and cause breakdowns.

Can a damaged evaporator affect the compressor?

Yes, it can. If the evaporator doesn’t work right, liquid refrigerant might reach the compressor—and that’s bad. The compressor is built to handle gas only, and liquid can damage it, which could mean an expensive repair or full system failure.

What type of evaporator is best for industrial systems?

Flooded or shell-and-tube evaporators are an excellent fit for large, always-running systems. They handle heavy loads and deliver intense, steady cooling. The right choice depends on your setup, but these types are popular in factories, cold storage, and big commercial chillers.