Truck Refrigeration Unit Work Principle

Dec 11, 2024

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Truck refrigeration units (commonly called reefer units) are essential for transporting temperature-sensitive goods such as food, pharmaceuticals, chemicals, and flowers. These units ensure that the cargo remains at the desired temperature throughout the journey, preventing spoilage, contamination, or degradation.
Here’s a detailed breakdown of how truck refrigeration units work:

1. Basic Function of a Refrigeration Unit

Truck refrigeration units operate on the principles of thermodynamics to remove heat from the cargo area and expel it outside the truck. The key components of the system include the compressor, condenser, evaporator, and expansion valve. These components work together to cool the air inside the cargo area and maintain a consistent temperature.

2. Key Components of a Truck Refrigeration Unit

a. Compressor

Function: The compressor is the heart of the refrigeration system. It pressurizes the refrigerant gas, turning it from a low-pressure gas into a high-pressure, high-temperature gas.
Location: It is usually mounted on the front of the truck or at the refrigeration unit's engine, and it is powered by the truck's engine or an independent power source (e.g., electric motor or battery).

b. Condenser

Function: The high-pressure gas from the compressor travels to the condenser. Here, the gas releases heat and condenses into a high-pressure liquid. This process occurs by passing the refrigerant gas through a series of coils, where ambient air cools it down.
Location: The condenser is usually located on the truck’s exterior, often near the front of the refrigeration unit.

c. Expansion Valve

Function: The high-pressure liquid refrigerant flows through an expansion valve, where it is allowed to expand rapidly, reducing its pressure and temperature. This cools the refrigerant significantly before it enters the evaporator.
Location: Typically located between the condenser and evaporator.

d. Evaporator

Function: The evaporator is located inside the cargo area of the truck. As the cold, low-pressure refrigerant enters the evaporator, it absorbs heat from the air inside the truck, cooling it. The refrigerant evaporates into a gas as it absorbs this heat.
Location: Inside the truck’s cargo area, typically mounted on the ceiling to distribute cool air evenly throughout the space.

3. Refrigeration Cycle: The Step-by-Step Process

a. Compression

The cycle begins when the compressor compresses the refrigerant gas (often R-134a or R-404A), raising both its pressure and temperature. The compressor is typically powered by the truck’s engine.

b. Condensation

The high-pressure, hot refrigerant gas is sent to the condenser. Here, the refrigerant releases heat to the outside air (via the truck’s condenser coils) and condenses into a high-pressure liquid. This liquid refrigerant is now ready to move on to the next stage of the cycle.

c. Expansion

The high-pressure liquid refrigerant travels through the expansion valve, where its pressure is reduced. As a result, the refrigerant’s temperature also drops, turning it into a cold, low-pressure liquid.

d. Evaporation

The cold refrigerant enters the evaporator inside the cargo area. Here, it evaporates (turns back into a gas) by absorbing heat from the air inside the truck. As it absorbs heat, the cargo area’s temperature decreases, keeping the products cool or frozen. The refrigerant then returns to the compressor, and the cycle repeats.

4. Types of Refrigeration Units

Truck refrigeration units can be classified based on their power sources and cooling methods. The main types include:

a. Engine-Driven Refrigeration Units

Power Source: These units are powered by the truck’s engine via a belt drive. The truck’s engine runs the compressor, making these systems efficient during long trips.
Application: Suitable for long-haul trucking where the engine runs for extended periods. The system is ideal for refrigerated transportation over long distances.

b. Electric-Powered Refrigeration Units

Power Source: These units are powered by an external electric motor, usually connected to the truck’s battery or a separate power unit. They are ideal for urban deliveries or short-range transport, where the truck’s engine is not running continuously.
Application: Common in fleet operations where trucks are docked for long periods or used for short trips.

c. Hybrid Refrigeration Units

Power Source: Hybrid systems use a combination of both electric power and engine power. This gives the flexibility of switching between power sources based on operating conditions.
Application: Hybrid units are suitable for mixed driving conditions where both long-distance and short-range operations are needed.

Conclusion

Truck refrigeration units are an important part of modern logistics and can safely and efficiently transport goods with high temperature requirements. As a professional truck refrigeration unit supplier, Kingclima offer 7*24 professional and patient help, if you need, please contact us at any time.

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