There are now five types of refrigeration systems that are frequently utilized in road transportation, including
(1) Coldwater System
(2) Dry Ice Refrigeration System
(3) Cold Plate Refrigeration System
(4) Liquid Nitrogen Refrigeration System
(5) Mechanical Refrigeration System System
There are various variations among the five different refrigeration systems. Guchen Thermo has summarized each system below in order to help you comprehend it better.
1. Coldwater Refrigeration System
Ice melts at 0 degrees Celsius under air pressure. Ice and salt are employed when a temperature of fewer than zero degrees Celsius is necessary. Salt decreases water’s melting point, hence the melting point would be lower the more salt was added to the freezing water within a specified range. It has been demonstrated that adding salt to ice water will lower the melting temperature of the ice to the lowest value of -21.2°C when the salt’s quality is equal to 29% of that of the ice water.
Ice water with varying salt contents is chosen for refrigerated transport in line with the required temperature of the refrigerated items. For instance, by using salt ice water with a 22% salt content, the compartment’s temperature can be kept between -18°C and -13°C.
Benefits: A chilled water refrigeration system is inexpensive to install and maintain.
Cons: Because ice water absorbs less latent heat than other types of water, chilled-water refrigeration systems only have a limited impact on the cooling of vehicle compartments. Salt and ice combined will also damage the carriage, contaminate the environment and chilled food, dampen the cargo, and pollute the environment.
In summary, fish and other aquatic items are mostly transported refrigerated using chilled-water refrigeration systems.
2. Dry Ice Refrigeration System
Benefits include minimal running costs, a straightforward design, and ease of use for the dry ice refrigeration system. Dry ice functions as an efficient cooling technology due to its low temperature and direct sublimation to gas.
It can achieve a lower temperature and a higher cooling capacity as compared to chilled-water refrigeration. So, for the transportation of frozen foods, the dry ice refrigeration method is appropriate.
Cons: The CO2 gas created by the sublimation of dry ice might decrease fruit and vegetable respiration, impede the multiplication of microbes, and slow down the oxidation of fat.
However, icing can readily result from dry ice sublimation, and too much CO2 gas would cause breathing problems and the necrosis of chilled foods like fruits and vegetables.
Furthermore, it is challenging to regulate the temperature in the compartment, and using dry ice is expensive and inefficient.
3. Cold PlateRefrigeration System
Cold plates are pre-chilled before transit in order to cause the refrigerant to freeze. The chilled refrigerant in the cold plates melts and absorbs heat from the surroundings during the transportation of refrigerated goods, maintaining the temperature of the goods.
The integrated type and split type of cold plate refrigeration systems are distinguished structurally.
The power unit, cold plates, and refrigeration unit are all mounted on the refrigerated vehicle in the integral system. There is only a refrigerated unit and cold plates in a split system. The power system operates the refrigeration unit to freeze the cold plates when the vehicle is parked.
A salt brine/eutectic solution with a melting point that is typically around 10°C lower than the temperature within the compartment is the most widely utilized refrigerant. Depending on the required temperature of the products being carried, the eutectic solution’s component amounts should be adjusted.
A portion of the carriage is taken up by the cold plate mechanism itself because it is bulky and heavy. Additionally, the body’s temperature is maintained by conventional cold plate systems throughout daily delivery runs of 8 to 15 hours.
In conclusion, short- to medium-distance refrigerated transportation in light or medium trucks are best served by cold plate refrigeration technology.
4. Liquid Nitrogen Refrigeration System
In order to cryogenically cool food, the system will use liquid nitrogen vaporization to absorb heat from the compartment. Liquid nitrogen has a boiling point of -196°C and a latent heat of vaporization of 200kJ/kg at atmospheric pressure. Nitrogen has a specific heat of 1.05J/g K. The amount of heat absorbed is roughly 358kj when liquid nitrogen is evaporated and heated to -20°C. Since liquid nitrogen is a byproduct of the creation of oxygen and has a low boiling point, it has seen extensive use.
Liquid nitrogen has a great refrigeration capacity, and rapid refrigeration, and is suitable for quick freezing. Its refrigeration mechanism has a simple structure, stable operation, and produces no noise or pollution. The evaporation of liquid nitrogen won’t cause the compartment to become moist, and nitrogen is helpful for preserving food quality. Additionally, refrigeration using liquid nitrogen has a fine temperature control range (+/-2°C). However, because liquid nitrogen is expensive and needs to be recharged frequently, there are some limitations on how it may be promoted.
5. Mechanical Compression Refrigeration System
Mechanical refrigeration is the refrigeration cycle method that is employed the most frequently among the five various types of road transport refrigeration systems because of considerations including transport distance and duration, supporting infrastructure and operating costs.
Mechanical refrigeration equipment is widely used primarily because the refrigeration unit can offer excellent refrigeration performance with a heating option, considerably expanding the application spectrum.
Temperature adjustments for compartments can be made automatically and precisely. Consider truck reefer units, which may be used to transport a variety of refrigerated commodities and have a temperature range of +30°C to -30°C.
Mechanical refrigeration systems are still the most dependable and efficient refrigeration methods utilized in the global cold chain industry, despite having somewhat complex architecture and expensive purchase/operation expenses.