1、 Structure comparison of water cooling and air cooling
Air cooling unit adopts air cooling mode (fan cooling); The water cooling unit adopts the cooling water cooling mode, and the water pump, cooling tower and circulating pipeline are used for circulating cooling of the unit.

From the perspective of water cooling installation mode, it can be divided into internal water cooling and external water cooling. As for the built-in water cooling, it is mainly composed of radiator, water pipe, water pump and enough water source, which means that most of the water cooling and heat dissipation systems are "bulky" and require sufficient space inside the chassis. Therefore, the air-cooled unit only needs the air-cooled condenser, namely, the fan. The water-cooled chiller shall be equipped with cooling tower, water pump and circulating pipeline. Water cooling is structurally more complicated than air cooling.

The air-cooled refrigeration unit is applicable to the regions where the water source is tight, and it is more favorable to use the air-cooled refrigeration unit for the refrigeration system with longer annual operation hours. The annual comprehensive cost of air cooling refrigeration unit is lower than that of water cooling system. However, if the water cooling system is properly managed and the amount of water make-up is controlled below 3%, the annual cost of water cooling unit is lower than that of air cooling system.

2、 Advantages and disadvantages of water cooling and air cooling systems:
Water cooling system: for the open cooling circulating water system, as the cooling water absorbs heat, contacts with the air, CO2 escapes into the air, and the dissolved oxygen and turbidity in the water increase, there are four major problems in the cooling circulating water system: corrosion, scaling, bacteria and algae breeding 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 the energy will be wasted. Therefore, it is very important to treat the system water with corrosion inhibition, scale inhibition, sterilization and algae elimination.

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

3、 Technical and economic comparison of two units
Example 1: 20HP Beezel medium and high temperature compressor 4NCS20.2 has a cooling capacity of 38.6KW and a power of 13.65KW when the evaporation temperature is 0 ℃ and the condensation temperature is 50 ℃, while the cooling capacity of water cooling is 44.5KW and the power is 12.1KW under the same working condition. In terms of cooling capacity and power consumption, it is slightly better than the air-cooled unit. However, the cooling tower fan power has not been included in the calculation.

Example 2: Compare a water cooled refrigeration unit with an air cooled refrigeration unit with the same host and evaporator. The annual operation time of compressor is 1000 hours to 3000 hours, and that of cooling tower and water pump is 1400 hours to 4200 hours.

Operation cost of air cooling refrigeration unit: annual power consumption cost of air cooling refrigeration unit=(compressor power consumption+fan power consumption) × Operation time/year × Electricity price.

Operating cost of water-cooled refrigeration unit:

Annual water cost of water-cooled refrigeration unit=(total circulating water × Water change times+water supplement amount × Total circulating water volume × Operation time/year) × Water price.
Annual power consumption of water-cooled refrigeration unit=(power consumption of compressor+power consumption of cooling tower fan+power consumption of cooling water pump) × Operation time/year × Electricity price.

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