Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services.
Vapour-Compression Refrigeration in Refrigerated Transport
Vapour-compression refrigeration (VCR) is the most common method used in the air conditioning of buildings and vehicles, including refrigerated transport vehicles. Cold is simply the absence of heat, thus, refrigeration lowers the temperature by removing the heat from an enclosed space, and releasing it somewhere else. VCRs use refrigerant, which circulates around the system, absorbing heat to be released outside. A simple VCR system consists of four components.
- Compressor – The first component of a VCR system is the compressor. The refrigerant enters the compressor as saturated vapour, which is then compressed to a higher pressure and temperature to create superheated vapour. This then moves into the next component.
- Condenser – The condenser consists of cooling water, or air flowing across tubes or coils. As the superheated vapour passes through the condenser, it releases the heat from the system, which is removed by the air or water. The condensed refrigerant is now in liquid form, known as a saturated liquid.
- Thermal Expansion Valve – The saturated liquid goes through the thermal expansion valve next. Here, a reduction of pressure occurs, leading to a flash evaporation of some of the liquid. This flash evaporation event also serves to lower the temperature of the now liquid and vapour mixture, making it colder than the space being refrigerated.
- Evaporator – The mixture is then carried into the evaporator, where warm air from a fan flows over the mixture and evaporates the remaining liquid. The air flowing across the mixture is also cooled and circulated around the enclosed space being refrigerated, lowering the temperature as desired. The vapour is then cycled back into the compressor to begin the cycle all over again.
Refrigerants Used for Refrigerated Transport
Most VCR systems in refrigerated transport use hydrofluorocarbons (HFCs) as a refrigerant. The R-404a and R-134a are the most common types of HFC used in the refrigerated transport industry.
Maintaining Your VCR System
It is important to properly maintain your VCR system, to avoid damages and increased operational costs, especially when the issues are related to the compressor. Compressors are quite expensive to repair, and should be checked regularly. A few issues to look out for in a VCR system include:
- Improper lubrication.
- Slugging – this occurs when a liquid mixture of refrigerant and oil, instead of vapour, enters the compressor cylinder.
- Fouling – this occurs when the condenser tubes and the evaporator surface are not kept clean, leading to a build-up of sediment, algae growth, or slime. This could lead to pressure problems, increasing the amount of energy used by the compressor.
- Motor inefficiency – dirty air passages and blocked filters could cause a decrease in the efficiency of the system’s motor. This means that the motor consumes more energy than it is supposed to. Comparing the voltage and amperage readings of the motor should allow you to detect any decreases in efficiency.
At Glacier Vehicles, we provide top of the line maintenance checks on our whole range of refrigerated vans. Visit us for the best experience our decades of unparalleled knowledge and experience can offer.