The refrigerator has greatly improved people's living standards and quality. With a refrigerator, we can eat all over the world without going out. The refrigeration unit equipment is heavy and large, occupying some volume of the carriage, and the cold plate can only work for 8-15 hours at a time.

Therefore, cold plate refrigeration is suitable for light refrigerated trucks to be used in medium to short distance transportation. In recent years, with the increasingly prominent issues of energy and environmental pollution, the application of cold plate refrigeration has developed rapidly and has become a refrigeration mode second only to mechanical refrigeration.

Dry ice refrigeration operates at one atmosphere pressure, with low temperature and high heat absorption. Therefore, it can serve as a compartment cooling source, not only achieving lower temperatures but also larger cooling capacity. Therefore, the refrigeration method is suitable for the transportation of frozen food in the freezer.

Dry ice refrigeration equipment is simple, with low investment and operating costs, easy to use, and the goods will not get wet. Dry ice can increase the production of CO gas, thereby inhibiting the growth of microorganisms, slowing down fat oxidation, and damaging the respiration of fruits and vegetables.

However, an increase in dry ice may lead to frosting, excessive carbon dioxide gas can cause breathing difficulties and necrosis of frozen foods such as fruits and vegetables, the temperature of thermostats is difficult to adjust, and dry ice is expensive and consumed in large quantities, making it less commonly used in practical applications.

Under normal pressure, the melting point of ice is 0 ℃. Adding salt to water ice can lower its melting point. In some ranges, the higher the salt water content of ice, the lower its melting point. When the mass of salt is 29% of the mass of water ice, the melting point of the mixture can reach a relatively low -21.2 ℃. If salt is added, the melting point will not decrease.

Usually, different compositions of salt ice are selected based on the temperature of refrigerated truck cargo transportation. For example, salt ice containing 22% salt can keep the temperature of the capsule between -18 ℃ and -13 ℃.

Water (salt) ice refrigeration equipment has low investment and operating costs, but ordinary water (salt) ice has low heat absorption per unit mass and limited cooling in the carriage. In addition, the melting of salt ice can pollute the environment, causing corrosion and moisture to food, trucks, and valuable goods. So water (salt) is first stored and transported in cold storage for fish and other aquatic products.