How to choose air cooling, water cooling and evaporative cooling?

Update:21-01-2020
Summary:

1. System structure: Air-cooled units use air cooling ( […]

1. System structure:

Air-cooled units use air cooling (fan cooling); water-cooled units use cooling water cooling, water pumps plus cooling towers and circulation pipelines to cool down the units. Therefore, air-cooled units only need air-cooled condensers or fans. The water-cooled chiller needs to be equipped with cooling towers, water pumps and circulating pipes. Structurally, water cooling is more complicated than air cooling.

Scope of application:

The air-cooled refrigeration unit is suitable for the area where the water source is tight; it is more advantageous to use the air-cooled refrigeration unit for the refrigeration system with longer annual operating hours; the annual comprehensive cost of the air-cooled refrigeration unit is lower than the water-cooled system, but if the water-cooled system is managed In the method, if the water supply is controlled below 3%, the annual cost of the water-cooled unit is lower than that of the air-cooled system.

The air-cooled chiller adopts air cooling method, which eliminates the cooling tower, cooling water pump and piping system necessary for the cooling water system, avoids condenser scaling and water pipe blockage in areas with poor water quality, and saves water resources. Among the current refrigeration equipment products, the most economical and simple model for maintenance and repair.

Third, look at the amount of cold:

For example, 20HP BITZER medium and high temperature compressor 4NCS20.2, with an evaporation temperature of 0 degrees and a condensation temperature of 50 degrees, has a cooling capacity of 38.6KW and a power of 13.65KW, while water cooling has a cooling capacity of 44.5KW and a power of 12.1KW at the same operating conditions. . In terms of cooling capacity and power consumption, it is slightly better than air-cooled units. However, the cooling tower fan power of the water-cooled water pump power has not been added to the calculation.

Disadvantages of water cooling system: For the open cooling circulating water system, after the cooling water absorbs heat, it comes into contact with the air, CO2 escapes into the air, and the dissolved oxygen and turbidity in the water increase, causing 4 major problems in the cooling circulating water system: corrosion, condensation Scale, bacteria and algae breed and sludge. If the water quality is not treated, the refrigeration equipment will be seriously damaged, the heat exchange efficiency will be greatly reduced, and energy will be wasted. Therefore, it is very important to treat the system water with corrosion inhibition, scale inhibition, sterilization and algae killing.

Disadvantages of air-cooled systems: The unit power consumption of air-cooled refrigeration units is slightly higher than that of water-cooled units, but the annual comprehensive cost of air-cooled units is basically the same as that of water-cooled units. The technical and economic analysis results show that it is reasonable to configure air-cooled condensers for medium and small refrigeration units. The longer the annual operating time of the refrigeration unit, the more favorable it is to use air-cooled condensation.

According to the research results of research institutes on the economics of air-cooled, water-cooled, and evaporative condenser systems, the test results show that:

Compared with air-cooled and water-cooled condensers, the evaporative condenser saves about 1/2 power consumption, and the circulating water volume only accounts for 1/8 of the water-cooled condenser. Through experimental evaluation, the superiority of the water-cooled condenser and evaporative condenser refrigeration system The cooling medium is excellent in heat transfer performance of the condenser. The evaporative condenser has better heat dissipation performance than the water-cooled type. The water-cooled condenser refrigeration system and cooling capacity are larger than the evaporative condenser. However, the evaporative condenser has the lowest unit refrigeration cost and the best performance.

The air-cooled condenser is the simplest to operate and maintain, and the equipment investment is small. It is suitable for application in areas where water resources are scarce. Evaporative condensers are more energy-efficient than air-cooled and water-cooled condensers, save water and have a superior system. Water-cooled condensers are suitable for occasions with large condensing loads and high ambient temperatures.

For applications, the evaporative condenser can be used in large refrigeration units such as screw and screw and piston parallel systems. (The corresponding method is one unit and one evaporative cooling); and water cooling is suitable for medium and small systems. One tower can be used for multiple units; while air cooling is used in small and medium-sized units, one condenser and one unit.