What is an Evaporator in a Refrigeration System?
An evaporator is a component of a refrigeration system that absorbs heat from the surrounding air, product, or space being cooled.
In the refrigeration cycle, the role of the evaporator is heat exchange, which takes place at the final stage, allowing the system to maintain low temperatures in cooling applications.
What is the Working Principle of Evaporator Coil(Air Cooled)
Before you start, please check what a refrigeration system/what an air-cooled condenser.
The evaporator receives low-pressure, low-temperature refrigerant from the expansion valve.
It evaporates by absorbing heat from the surrounding air or objects inside the cooling space, which lowers the cooled area’s temperature and heats the refrigerant vapor to continue the cycle.
The efficiency of the evaporator is closely related to the material and spacing of the copper tubes and fins.
Miracle’s full range of evaporators uses internal thread copper tubes. At the same size, Miracle evaporators have stronger cooling capacity.
What is the Function of the Evaporator in the Refrigeration System?
The air-cooled evaporator works as a heat exchanger in a refrigeration system where it absorbs heat and transfers it from the cooled space air into the refrigerant inside the evaporator coils.
So when the refrigerant absorbs this heat, it evaporates, changing from a low-temperature, low-pressure liquid into a gas.
It is then sent to the compressor to complete and continue the refrigeration cycle.
In this process, the evaporator works with an expansion valve that regulates the refrigerant flow into the evaporator, ensuring it enters at the right pressure and temperature.
The refrigeration compressor pulls the vaporized refrigerant from the evaporator and compresses it into a high-pressure gas.
The evaporator also coordinates with a refrigeration condenser that releases the absorbed heat from the refrigerant, allowing it to return to a liquid state and re-enter the cycle.
Check what the difference is between the evaporator and condenser in the refrigeration system?
What Types of Evaporators Are Used in Refrigeration?
Check the Refrigeration Evaporator to help you know more details. The types include dual-discharge evaporator, cubic air-cooler, and angled air-cooling evaporator.
Different types of evaporators in refrigeration systems are based on defrosting methods, cold storage temperature, size, and structural design.
The most important factor is how the evaporator removes frost, affecting system efficiency, performance, and maintenance needs.
Types of Evaporators by Defrosting Method:
In refrigeration system operation, moisture in the air freezes on the evaporator coils, reducing heat transfer efficiency.
Evaporators use different defrosting methods to remove ice buildup and maintain proper performance.
Miracle evaporators can be used in cold rooms and walk-in coolers (freezers); please see more types of evaporators.
- Electric Defrost Evaporator(Air Cooled):
An electric defrost air-cooled evaporator uses heating elements to melt accumulated frost on the evaporator coils.
It is low-cost, easy to install, and requires simple piping, making it ideal for various refrigeration applications, such as commercial refrigeration, walk-in coolers, food storage facilities, etc.
- Water Defrost Evaporator(Air Cooled):
The water-defrost air-cooled evaporator uses a water spray system to remove frost from the evaporator surface quickly.
It provides rapid defrosting, lowers maintenance costs, and maintains a stable cold storage temperature.
This type of evaporator is suitable for large refrigeration systems where fast and efficient defrosting is required.
- Hot Gas Defrost Evaporator(Air Cooled):
A hot gas defrost air-cooled evaporator uses a hot refrigerant gas from the system to melt ice buildup on the evaporator coils.
This is safer, comparatively energy efficient, and maintains stable cold room temperatures that reduce defrost time.
This type of evaporator has energy-saving benefits, and it is gradually becoming trendy in refrigeration defrosting technology.
Types of Evaporator by Cold Storage Temperature:
Why is the evaporator also categorized based on the temperature range of the cold storage facility?
Because different temperature requirements determine the fin spacing of the evaporator coils, affecting heat transfer efficiency, frost buildup, and cooling performance.
There are three types of evaporators based on cold storage temperature:
- High-Temperature Evaporator:
This type of evaporator is designed for cold storage rooms operating between 5°C and 15°C and has a fin spacing of 4.5mm. This small spacing allows for better airflow in moderate-temperature environments.
This type is commonly used for pre-cooling storage, fresh food storage, preserving temperature-sensitive products, and other industries where maintaining consistent temperature and humidity is critical, like wine, chocolate, seed storage, and vegetable preservation.
- Medium-Temperature Evaporator:
This medium-temperature evaporator is designed for cold storage rooms ranging from -5°C to 5°C. The fin spacing is 6mm, optimized for moderate frost accumulation.
It is suitable for storing frozen foods that have already been frozen, maintaining their freshness without excessive ice formation.
- Low-Temperature Evaporator:
This works for freezer storage rooms between -8°C and -25°C. It is used in applications where deep freezing is required to maintain product quality, such as meat, beef, lamb, fish, poultry, and frozen goods storage.
Evaporator Types by Structural Design:
Why are evaporators also classified based on their structural design and materials?
Different designs are suitable for different cold storage and refrigeration applications, where different designs, cooling speeds, and storage conditions impact cooling efficiency, space utilization, and installation complexity. Let’s see what the types are:
- Air Cooler Evaporator:
This type’s structure is simple, and installation is easy, making it a common choice for many commercial and industrial refrigeration systems.
It has fewer pipe welding joints, making it affordable and easy to integrate into existing cooling setups.
This reduces the risk of refrigerant leaks and simplifies maintenance.
- Aluminum Row Evaporator:
This evaporator is mainly designed for large refrigeration systems where consistent temperature control is crucial.
It provides rapid cooling and helps maintain stable humidity levels in cold storage. Its aluminum construction ensures excellent heat exchange efficiency, preventing excess frost buildup.
- Aluminum Shelf Evaporator:
This evaporator type is suitable for high-energy-efficiency cold storage solutions and is used in warehouse-style cold rooms where optimizing storage capacity is a priority.
It maximizes storage space in cold rooms by integrating cooling surfaces with a shelving structure.
How to Choose the Right Evaporators for Food and Industrial Cold Rooms?
To correctly select an evaporator, you first need to understand the types of cold storage equipment. Here is a complete list of cold storage equipment.
As a heat exchange unit, the evaporator primarily provides a continuous supply of cooling energy to the cold storage facility. Therefore, the selection of the evaporator is crucial.
Evaporator selection depends on the cold storage temperature and type.
For example, -5~5℃ cold storage facilities should use evaporators with a 4.5mm fin spacing (for fruits and vegetables cold room); -15~-20℃ cold storage should use evaporators with a 6mm fin spacing (for meat cold rooms); -20~-25℃ cold storage should use evaporators with a 9mm fin spacing; and -35℃ blast freezers should use evaporators with a 12mm fin spacing.
This is because lower temperatures lead to more condensation. Using an evaporator with an incorrect fin spacing can cause severe frost buildup and reduced refrigeration efficiency.
Furthermore, the application scenario must be considered. For food factories, a dual-discharge evaporator and food-grade stainless steel evaporator should also be considered.
For more information on evaporator selection, please refer to our case studies.