Advantages and Disadvantages of Indirect Refrigeration System

Indirect refrigeration mainly transmits cooling capacity through a large circulation of secondary cooling medium at atmospheric pressure. In locations where direct refrigerants are not easily applicable or in special environments where direct refrigerants cannot be used, refrigerant carriers are often used instead of direct refrigerants to cool the cooled object.
In indirect refrigeration, only the refrigerant carrier enters the cold storage workshop and circulates at atmospheric pressure, which can avoid the hidden dangers of high pressure generated in the warehouse by direct refrigeration and the use of a large amount of unsafe refrigerants.
Working principle
In an indirect cooling refrigeration device, the heat in the cooled object or space is transferred to the refrigerant through an intermediate medium. This intermediate medium is called a refrigerant carrier in refrigeration engineering. The refrigerant carrier first exchanges heat with the refrigerant in the evaporator to obtain cooling capacity, and then a pump is used to transport the cooled refrigerant carrier to various cooling locations to cool the cooled object with the refrigerant carrier.
The advantage of using a refrigerant carrier is that the refrigeration system can be concentrated in the machine room or a very small area, greatly reducing the connecting pipes and joints of the refrigeration system, facilitating sealing and system leak detection, and thus reducing the volume of the refrigeration system and the filling amount of the refrigerant. Generally, substances with large specific heat capacity are selected as refrigerant carriers, and the temperature of the cooled object is easy to remain constant. In large-capacity and centralized cooling devices, the use of refrigerant carriers is convenient for solving the problems of cooling capacity control and distribution, and for the installation and operation management of the unit. The manufacturer can directly install the refrigeration system. The user only needs to install the refrigerant carrier system on site. The disadvantage is that the system is more complex than when no refrigerant carrier is used, and the heat transfer temperature difference between the cooled object and the refrigerant is increased. A lower evaporation temperature of the refrigerator is required, and the total irreversible heat transfer loss is increased.
Advantages of indirect refrigeration system:
①It can meet the requirements of small temperature difference, ensure the relative humidity in the warehouse and improve product quality.
②The refrigerant carrier has a large heat capacity, and the cooled object is easy to remain stable. The area of the cold air blower in the warehouse is about 20% larger than that of the direct evaporation type (only exists when the thermal expansion valve is used for liquid supply. If the fluorine pump is used for liquid supply, this point does not exist).
③The filling amount of the refrigerant can be reduced.

④Once the system leaks, the food will not be contaminated by the refrigerant.
⑤The requirements for the installation of systems such as ethylene glycol and valves are lower than those of direct refrigeration systems.

Disadvantages:
①The addition of intermediate medium cooling makes the evaporation temperature about 5℃ lower than that of the direct refrigeration system, and the refrigerating capacity is more than 20% less than that of direct cooling.
②The conveying device becomes more complex, and a conveying pump for conveying aqueous solutions such as ethylene glycol is added.
③To obtain different warehouse temperatures, a mixing pump and a three-way electric valve need to be added.
④The three-way electric valve is easily jammed due to icing during use.
⑤The freezing point and boiling point of most refrigerant carriers in indirect refrigeration are not ideal enough.

Some will even seriously corrode metals, resulting in increased daily maintenance costs, short service life and increased energy consumption of the refrigeration system. Therefore, to ensure the normal operation of the indirect refrigeration system, a good refrigerant carrier and a refrigerator need to be matched.