The emergence of refrigerated trucks has greatly improved people's living standards and quality. With refrigerated trucks, we can eat all over the world without leaving our homes. So, how much do you know about refrigerated trucks? Do you also know their cooling methods? Below, the refrigeration unit editor will take you to briefly understand.

1. Dry ice refrigeration

At atmospheric pressure, dry ice has a low sublimation temperature and high sublimation heat absorption. Therefore, using it as a cooling source for the carriage can not only achieve lower temperatures but also larger refrigeration capacity. Therefore, this refrigeration method is suitable for the transportation of frozen and refrigerated food.

Dry ice refrigeration equipment is simple, with low investment and operating costs, easy to use, and the goods will not get damp. The CO gas produced by dry ice sublimation can control microbial growth, slow down fat oxidation, and weaken the respiration of fruits and vegetables.

However, sublimation of dry ice can easily cause frosting; Excessive CO2 gas can cause difficulty breathing and necrosis of refrigerated items such as fruits and vegetables; Difficulty adjusting the temperature inside the cabin; Dry ice has a high cost and a large consumption, so its practical application is limited.

2. Cold plate refrigeration

The cold plate device itself is heavy and has a large volume, occupying some of the volume of the carriage. Moreover, the cold plate can only work continuously for 8-15 hours after being charged once. Therefore, cold plate refrigeration is suitable for medium and light refrigerated vehicles for 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 the second only refrigeration method after mechanical refrigeration.

3. Water ice and salt ice refrigeration

Under atmospheric pressure, the melting point of ice is 0 ℃. The heat absorption during ice melting is 334.8 kJ/kg. Adding salts to water ice can lower its melting point. In some ranges, the more salt in water ice, the lower the melting point.

Experimental results have shown that when the mass of salt added is 29% of the mass of water ice, the melting point of the mixture can reach a low value of -21.2 ℃. If the salt content is further increased, the melting point will no longer decrease. Usually, different components of salt ice are selected based on the appropriate temperature for transporting refrigerated goods. For example, by using salt ice with a salt content of 22%, the temperature inside the carriage can be maintained at -18 to -13 ℃.

The water ice refrigeration unit has low investment and operating costs, but the heat absorption per unit mass of ordinary water (salt) ice is relatively small, and the cooling inside the carriage is limited. In addition, the melting of salt ice will pollute the environment, food, corrode the carriage, and cause moisture to the goods. Therefore, water (salt) ice refrigeration is mainly used for the refrigerated transportation of fish and other aquatic products.