Typically, central Cold Storage warehouses, whether refrigerated or frozen, either use centralized parallel rack refrigeration systems with several compressors acting as a network, or industrial chiller systems. These systems can be installed physically separate from the actual Cold Storage rooms and connected to the individual Cold Storage rooms using a system of pipes. Refrigeration regulators can be deployed for solenoid valve control such that each evaporator in the rack system can be regulated individually.

Parallel Racks … Parallel Rack Compressor Systems feature multiple compressors that all work together to suffice required refrigerated loads. This type of system is applied to many different industrial applications, the most common being Cold Storage refrigerated and freezer warehouse and distribution center space as well as food and beverage processing facilities. These facilities can include multiple coolers, freezers, and refrigerated loading docks. Parallel compressor racks can be set up for multiple suction groups. A single parallel rack for a smaller Cold Storage facility could be designed with a low-temperature suction group to provide refrigeration for the freezer as well as a medium-temperature suction group to provide refrigeration for the coolers and refrigerated loading dock. Dedicated low-temperature and medium-temperature racks can be utilized for larger, more complex Cold Storage facilities.

Parallel Systems or “Racks” provide significant advantages over other refrigeration methods.  The most notable of these are:

• Energy Efficiency —By using multiple compressors and computer optimization, the compressors cycle on and off to continuously match the exact cooling requirements and thereby save energy by not being forced to run only to maintain a working pressure.
• Compressor Redundancy — Through the use of multiple compressors, all working together to maintain the required load, there is an inherent redundancy created.  If a compressor failure occurs, there are additional compressors to distribute the load which results in minimal deviation from design temperature.
• Flexibility — Systems are custom-designed to match the exact requirements of the intended application.  Moreover, through flexibility of compressor staging and computer controls, future load additions or temperature changes can be easily accommodated.

Advances in technology have made the use of environmentally friendly CO₂ booster systems practical across a wide range of applications. A booster system uses only CO₂ as a refrigerant. Unlike other parallel rack systems, it does not have to rely on any HFC or ammonia refrigerants. In large part, this is made possible by the function of two main components that are not found on traditional types of systems — a high-pressure control valve and a flash-gas bypass valve. In tandem with a third component, the condenser/gas cooler, which works as a condenser like the ones on most other types of systems, CO₂ booster systems have become a practical, efficient alternative to traditional systems for almost any type of application in any locale.

Chillers … The function of an industrial chiller is to move heat from one location (usually process equipment, product, or storage space) to another place (usually the air outside the facility). It is very common to use water or a water/glycol solution to transfer the heat to and from the chiller, which may require the process chiller to have a reservoir and pumping system. Water-cooled chillers are mostly used in large commercial and industrial facilities. These chillers are often located in a purpose-built plant room and connected to a remote heat dump outside. The system generates chilled water and pumps it to air-dispensing units located in the area being cooled.

The chilling process starts in the evaporator by absorbing the heat from the chilled water. Then the compressor extracts the refrigerant vapor from the evaporator. Following that, the compressor pumps this vapor into the condenser. The refrigerant condenses and releases the heat into the cooling water or air. Then the liquid refrigerant, which was created due to refrigerant condensation, continues moving to the expansion valve, which controls and adjusts its flow rate, and then eventually back into the evaporator. The liquid’s high pressure is reduced along the way together with the temperature. As a result of the process, the chilled water transfers its thermal energy to the refrigerant.