Evaporative-cooled screw chiller

The evaporative‑cooled screw chiller is an integrated unit. It mainly consists of screw compressors and an evaporative condenser. It integrates the functions of main unit, cooling tower and cooling water pump. No external cooling tower or cooling‑water pipeline is required. Only chilled‑water piping and power supply need to be connected on‑site for operation. It dissipates heat by utilizing the latent heat of water evaporation, combining the high efficiency of water‑cooled units and the easy installation of air‑cooled units. It is widely used in large‑and‑medium‑size process cooling and central air‑conditioning applications.

1. Working Principle

1. Compression: The screw compressor compresses low‑temperature, low‑pressure refrigerant into high‑temperature, high‑pressure gas.
2. Condensation (core of evaporative cooling): The high‑temperature refrigerant flows into the evaporative condenser. Spray water forms a water film on the outer surface of copper tubes, and fans draw ambient air. Heat is removed through water evaporation, and the refrigerant condenses into high‑pressure liquid. Part of the water evaporates and dissipates, while the remaining water flows back to the water collecting pan for circulating spraying.
3. Throttling: The high‑pressure liquid refrigerant is depressurized by an expansion valve.
4. Evaporation: The refrigerant enters the evaporator and absorbs heat from chilled water to produce cold water at about 7 °C. The refrigerant turns back into low‑pressure gas and returns to the compressor to complete the cycle.

Key point: Independent cooling‑tower heat exchange is eliminated. Its condensing temperature is 3‑4 °C lower than that of conventional water‑cooled units, and the unit COP increases by approximately 10%‑20%.

2. General Technical Parameters (Industry Standard)

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3. Advantages

1. Simplified system and lower initial‑installation cost: Eliminates cooling towers, cooling water pumps and cooling‑water pipe networks. Reduced investment in civil work, piping and power distribution, as well as shorter construction periods.
2. High comprehensive energy efficiency: Lower condensing temperature plus elimination of cooling‑water pump power consumption. The whole system is 10%‑20% more energy‑saving than conventional water‑cooled screw systems.
3. Water saving: Circulating spray water volume is only 30‑40% of that of conventional water‑cooled systems; evaporative water consumption accounts for 5‑15% of conventional water‑cooled systems. Suitable for water‑scarce regions.
4. Good adaptability under high‑ambient‑temperature conditions: Compared with air‑cooled screw chillers, it has smaller performance degradation and more stable cooling capacity in hot summer weather.
5. Proven reliability: Mature screw‑compressor technology supports long‑term continuous operation. Dual‑compressor units are available for operation redundancy.

4. Disadvantages

1. High requirements for outdoor installation: Units are placed on rooftops or outdoor platforms. Pipes are vulnerable to freezing in cold winters, so anti‑freezing measures and heat tracing are mandatory in cold‑climate areas. Condenser coils are prone to scaling and corrosion in rainy‑humid climates; regular cleaning and maintenance are required.
2. Larger footprint: Compared with indoor water‑cooled screw chillers plus separate cooling towers, the unit itself has larger overall dimensions. Sufficient space for installation and maintenance must be reserved on rooftops.
3. Water consumption for spraying: Make‑up water is still required; zero‑water consumption cannot be achieved. Heat‑exchange capacity drops slightly during high‑humidity plum‑rain seasons in southern China.
4. Higher noise level than indoor water‑cooled units: Large‑flow spray fans are built‑in. Noise‑reduction measures shall be considered for outdoor installation.

5. Applicable and Non‑applicable Scenarios

✅ Applicable scenarios‑ Process cooling for factories: Medium‑to‑large cooling‑capacity applications in chemical, pharmaceutical, plastic‑processing, food and other industries.‑ Commercial projects: Shopping malls, hospitals, hotels, where no proper mechanical room is available yet rooftop space is sufficient.‑ Water‑scarce regions and renovation projects where cooling‑tower layout is inconvenient.

❌ Non‑applicable scenarios‑ Severe‑cold regions without anti‑freezing conditions.‑ Sites with insufficient rooftop load‑bearing capacity or no outdoor installation space.‑ Locations adjacent to residential areas with strict noise‑limit requirements.

6. Comparison with Similar Chiller Types

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Precautions for Unit Use

Installation precautions

1. When lifting, positioning, and installing the unit, safety must be taken into account to prevent collisions and ensure the integrity of the equipment.

2. If the unit is installed outdoors, efforts should be made to avoid exposure to wind and rain (except for rainproof types), direct sunlight, or other heat sources that directly radiate; The computer room environment must be kept dry, clean, and ensure good ventilation, leaving space for unit maintenance and upkeep.

3. For air-cooled units, please ensure that there are no obstructions around the unit and reserve 1 meter of space; There is no obstruction within 2 meters of the top of the unit to ensure good ventilation.

4. It is recommended to install the unit on a strong and level ground, and install shock-absorbing rubber pads under the unit chassis to correct the level of the unit. If there are anchor bolts, they must be installed and fixed.

5. The circulating water pump used in conjunction with the unit should be selected and installed according to the data requirements such as water flow rate and water resistance required by the unit.

6. The water pump must be installed in front of the inlet of the unit, and it is recommended to install a filter at the inlet of the water pump to prevent foreign objects from entering the heat exchanger of the unit; If the unit is installed in areas with poor water quality, water treatment must be carried out first to avoid damage to the heat exchanger.  

7. It is recommended to install valves, water pressure gauges, thermometers, water flow switches, and other equipment for the water pipeline system connecting the unit, in order to facilitate the inspection and maintenance of the unit's daily operation.

8. To prevent air from being trapped in the water system, the air must be completely discharged before starting the compressor.

9. The chilled water pipeline must be insulated properly to avoid loss of cooling capacity, condensation, and freezing.

10. The weight of the system connection pipeline shall not be borne by the machine body. Rubber shock-absorbing flexible joints and gate valves shall be installed at the inlet and outlet of the unit to avoid vibration and facilitate maintenance.

11.When configuring wires for the unit, wires with slightly larger cross-sections (with margin) should be selected according to the power consumption, and reliable electronic control components and grounding power sources should be installed to prevent accidents such as overload and leakage.

12. As the unit is equipped with reverse phase and phase loss protection, attention must be paid to whether the line phase is correct during wiring installation. The unit cannot operate normally when the phase is misconnected or missing.    

13. The operator of the unit must observe the operation status of the unit at all times. Once any abnormal situation is found, please promptly troubleshoot. Forced operation will inevitably cause damage to the unit.

Precautions for operation:

1. Before starting up, check whether all water outlets and pipelines of the unit have been correctly installed and connected.

2. Before starting up, check if the power supply of the unit is connected and if the phase sequence is correct.

3. Before starting up, ensure the safety of the power and water sources. Please carefully refer to the equipment operation manual and strictly follow the instructions for use and operation.

Maintenance precautions:

1. Regularly replace the water in the water tank (it is recommended to replace it every 2 months).

2. Regularly clean the radiator of the unit. For air-cooled units, it is recommended to clean the radiator every 3 months; It is recommended to clean the shell and tube condenser and cooling tower of water-cooled units every 6 months (if the usage environment or water quality is poor, it is recommended to shorten the cleaning cycle).

3. If the unit is not used for a long time, please turn off the main power supply; When the ambient temperature is below 0 ℃ and the unit is shut down for more than 6 hours, the unit and pipelines may freeze, and the damage caused by this is not covered by the warranty. The best way to avoid pipeline freezing is to completely drain all the water in the unit system!

4. Regularly check the water quality on site to ensure that the water source is qualified (pH ≈ 7). If it contains corrosive substances and causes damage to the unit, it is not covered by the warranty.

5. When the unit encounters unavoidable faults during use, please inform our company of the unit model, component name, and other information so that we can provide you with services more quickly.

6. During the warranty period, our company promises to provide free maintenance services for the unit (excluding human damage, improper use, natural disasters, and uncontrollable factors).

Warning: This unit is a high-voltage, highly specialized mechanical equipment, and should be operated correctly by professional technicians strictly in accordance with the "User and Installation Manual".