When you see a large truck on the road with a humming device on the front wall of the bed, most likely it is carrying perishable goods inside it. Exactly refrigerator allows you to deliver fresh food, medicine or flowers over thousands of kilometers without loss of quality. This is a complex technical solution that turns an ordinary body into a mobile refrigerator.
Many people confuse the concept of a refrigerator with simple thermal insulation, but the difference between them is colossal. If a conventional van only slows down the heating of the cargo, then refrigeration unit actively maintains the set temperature, regardless of what is happening outside - heat +40°C or frost -30°C.
In this article we will analyze the design of the system, types of cooling and operating nuances. Understanding the principles of operation will help you choose the right transport for your business or avoid damage to cargo when transporting it yourself.
The main difference between a refrigerator and an isothermal van
The main misconception is that any insulated body is called a refrigerator. In fact, isothermal van — it’s just a “thermos” on wheels. Its walls are made of sandwich panels with polyurethane foam, which allows the cargo to remain warm for only a short time.
The refrigerator is equipped with an autonomous or driven refrigeration unit. It is an active system that produces cold (or heat) as needed. Temperature in the refrigerator can be precisely adjusted and maintained automatically throughout the trip.
⚠️ Attention: Using an isothermal van for long-term transportation of frozen products in the summer will lead to their spoilage, since without a working refrigerator the cargo will begin to thaw in a few hours.
The choice between the two types of transport depends on the duration of the flight. To distribute products around the city within 2-3 hours, an isotherm is often sufficient. However, for intercity transportation, where travel time is calculated in days, a full-fledged refrigerator.
The principle of operation of the refrigeration unit
The heart of the system is a refrigeration unit operating on the principle of a compression cycle. Circulates inside the circuit refrigerant (freon), which changes its state of aggregation, absorbing heat from inside the body and releasing it outside.
The process begins with a compressor, which compresses freon gas, raising its temperature. The hot gas then enters a condenser located outside, where it is cooled by a fan and turns into liquid. After passing through throttling device, the pressure drops sharply, the refrigerant boils and cools the evaporator inside the body.
The evaporator fan forces air through the cold fins, distributing the cooled flow throughout the entire volume. It is important to understand that the refrigerator does not “freeze” the air, but constantly removes heat coming through the walls or from the cargo itself.
- ❄️ Compressor - creates pressure and movement of refrigerant through the system.
- 🌡️ Capacitor - an external radiator that releases heat into the atmosphere.
- 💨 Evaporator — an internal unit that cools the air in the body.
- 🔄 Thermostat — controls the temperature and turns the unit on/off.
When loading a refrigerator, always leave a clear space (“green zone”) at the front wall under the evaporator so that air can circulate freely throughout the body.
Types of refrigeration units and energy sources
The choice of the type of refrigeration unit drive directly affects the economics of transportation and the scope of application of the equipment. There are three main categories, each with its own advantages for different logistics tasks.
First type - diesel units. They are completely autonomous, have their own fuel tank and do not depend on the car engine. This is an ideal option for long-distance flights and transportation of goods with strict temperatures, since the installation works even when the tractor engine is turned off.
The second type is installations driven by a car engine (engine driven). The compressor operates from the engine belt through a pulley. Such systems are cheaper to maintain, but only cool the cargo when the vehicle is moving. They are not suitable for parking and overnight stays without additional electric motors.
| Drive type | Autonomy | Fuel consumption | Best use |
|---|---|---|---|
| Diesel | Full | High | Long-distance transportation, freezing |
| From the engine | Only in motion | Low | Delivery around the city, refrigerated cargo |
| Electric | Network only | Depends on the tariff | Warehouse logistics, short routes |
Third option - electrical installations. They are quiet, environmentally friendly, but require connection to an external network of 220V or 380V. Often used in combination with diesel engines for operation in residential areas at night where noise is prohibited.
What is multi-temperature mode?
A multi-temperature refrigerator has partitions inside the body that divide it into compartments. Each compartment maintains its own temperature thanks to separate dampers and sensors. This allows you to transport ice cream (-18°C) and chilled meat (+2°C) at the same time.
Temperature conditions and classes of refrigerators
Not all cargo requires the same conditions. The international classification divides refrigerators into classes depending on the range of temperatures they maintain. This is a critical parameter for compliance with sanitary standards.
The most common class is AT (from +12°C to 0°C). It is used for transporting vegetables, fruits, flowers and chilled meat products. Avoiding freezing is important here, so thermostat accuracy is key.
For frozen products (meat, fish, prepared foods, ice cream) class settings are required BT or CT, capable of maintaining temperatures from -20°C and below. In such conditions, any breakdown of the installation threatens rapid damage to the entire cargo.
- 🥦 Refrigerated cargo - require maintaining a temperature above the freezing point of water.
- 🍦 Frozen cargo - require deep freezing and stability below -18°C.
- 💊 Pharmaceuticals — requires precise control, often in a narrow range (+2...+8°C).
⚠️ Attention: When transporting fresh flowers or certain types of fruits, do not direct the flow of cold air directly onto the cargo. This can cause cold burns and loss of presentation.
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Features of transportation of different types of cargo
Perishable food logistics is a science. Different products generate different amounts of heat and require different air exchange rates. For example, fresh fruits and vegetables continue to “breathe” after being picked, releasing heat and moisture.
For such cargoes it is necessary to enable the mode fresh air (fresh air), opening the damper to remove ethylene and excess moisture, otherwise the cargo will simply rot. At the same time, frozen foods require a sealed circuit and minimal air exchange.
Requires special attention pharmaceutical products. This often requires not only temperature control, but also keeping logs (records) of changes along the way. Modern refrigerators are equipped with telematics systems that transmit data to the dispatcher in real time.
When loading meat carcasses, it is important to use special hooks and slats to ensure air circulation on all sides. If you stack the boxes tightly to the ceiling, the cold will not reach the center of the stack, and there is a risk of spoilage.
Proper stowage of cargo to ensure air circulation is more important than the capacity of the refrigeration unit itself. Without circulation, the cold will not reach the center of the load.
Typical faults and maintenance
Like any complex equipment, refrigerators require regular maintenance. The most common problem is contamination of the condenser with lint, dirt and insects. This leads to overheating of the system and a decrease in cooling efficiency.
The second common problem is leakage refrigerant. If you notice oil on the tubes or hear hissing, it means the seal is broken. The installation cannot be operated without freon - this will lead to compressor failure.
Problems with drive belts (in engine driven systems) and depressurization of the body are also common. Cracks in the foam or damage to the door seals negate the work of even the most powerful installation.
- 🔧 Daily — visual inspection of the cleanliness of the condenser and the operation of the fans.
- 📅 Quarterly — checking the tension of the belts and the condition of the electrical wiring.
- 🛠️ Annually — complete system diagnostics, filter replacement and leak testing.
⚠️ Attention: Never wash the condenser (radiator at the front of the body) with a Karcher under high pressure. You can bend the aluminum plates, which will completely disrupt the airflow and lead to overheating.
Timely replacement of filters and oil in the compressor extends the life of the unit by years. Remember that repairing a refrigeration unit on the road always means downtime and the risk of cargo loss, so prevention is more cost-effective.
Why does the installation hum and turn off?
Frequent switching on and off (clocking) may indicate an incorrect thermostat setting, a lack of refrigerant, or too little body load when the volume of cold air quickly cools the sensor.
Frequently asked questions (FAQ)
Is it possible to use a refrigerator in the summer as an isotherm by turning off the refrigeration unit?
Technically possible, but not recommended. The design of the refrigerator has a smaller thickness of insulation compared to professional isotherms, since the calculation is made for the operation of the refrigerator. Without a working unit, the cargo will heat up faster than in a specialized insulated van.
What is the average temperature inside the refrigerator at +30°C outside?
A properly functioning installation is capable of maintaining a temperature difference (delta) of 40-50 degrees or more. That is, at +30°C outside it’s easy to get -20°C inside. However, the time to reach the mode depends on the preliminary preparation (pre-cooling) of the body.
Is it necessary to warm up the refrigerator in winter?
Yes, before starting work in severe frosts, it is recommended to let the unit idle to warm up the oil in the compressor. Cold, thick oil may not have time to lubricate the rubbing parts in the first seconds of starting under load.
What to do if the refrigerator stops freezing during a flight?
First of all, check to see if the fuse is blown and if there is fuel. If everything is visually in order, but there is no cold, do not try to repair a complex system yourself without skills. Contact the service, store the cargo (cover with blankets) and record the temperature for insurance.