Structure and Working Principle of Air Cooled Screw Chiller

Air cooled screw chillers refer to chiller units that use screw compressors as power equipment. These chillers employ air-cooled heat dissipation methods. Unlike water-cooled units that require an external cooling tower or cooling water system, air cooled screw chillers rely on built-in fans and finned condensers to exchange heat directly with the surrounding atmosphere, dissipating the heat generated during refrigeration into the air.

Structure of Air Cooled Screw Chiller Units

Screw Compressor

This is the core component of the air cooled screw chiller unit. It uses one or more pairs of intermeshing rotors (typically male and female screws) for volumetric compression, compressing low-pressure, low-temperature refrigerant gas into high-pressure, high-temperature gas.

Condenser

The high-pressure refrigerant gas enters the condenser, where it exchanges heat with the air through fins, dissipating heat into the environment and condensing into high-pressure liquid.

Evaporator

The high-pressure liquid refrigerant enters the evaporator through an expansion valve (such as an electronic expansion valve), absorbing heat from the circulating water or air passing through the evaporator as it evaporates and transitions into low-pressure gas.

Expansion Valve

It automatically adjusts the flow of refrigerant based on system conditions, throttling the refrigerant to lower its pressure and converting it into a gas-liquid mixture before it enters the evaporator.

Four-way Reversing Valve (not required in all systems)

Used in some systems to switch the direction of refrigerant flow, enabling modes for cooling, heating, or defrosting.

Receiver

Stores and supplies a certain amount of liquid refrigerant, preventing liquid slugging while also serving as a gas-liquid separator.

Dryer Filter

Removes moisture and impurities from the refrigerant, protecting the compressor and other refrigeration components from corrosion and mechanical damage.

Heat Exchanger (or heat recovery device)

Some models may be equipped with this to recover waste heat generated during refrigeration, using it for heating domestic water or other purposes.

Electrical Control System

Includes controllers, sensors, actuators, etc., responsible for monitoring the operating status of the unit and adjusting the operating parameters of various components to ensure stable and efficient operation of the system.

Fan

Forces air movement to enhance the heat dissipation effect of the condenser.

Auxiliary Equipment

Such as water pumps, valve assemblies, chilled water supply tanks, chilled water return tanks, overflow structures, etc., used for the circulation, distribution, and water balance adjustment of the chilled water system.

Air Cooled Screw Chiller Working Principle

The working principle of industrial screw chillers mainly includes the following four basic processes:

Compression Process

The screw compressor sucks in low-pressure, low-temperature refrigerant gas produced in the evaporator and compresses it to a high-pressure, high-temperature state through the rotation of the rotors.

Condensation Process

The high-pressure, high-temperature refrigerant gas enters the condenser, where it dissipates heat through the air blown by the fan, cooling the refrigerant from gas to liquid state.

Throttling Process

The high-pressure liquid refrigerant passes through the expansion valve to throttle and lower the pressure. Accompanying the pressure drop, the temperature of the refrigerant also decreases, converting into a low-pressure, low-temperature gas-liquid mixture.

Evaporation Process

The low-pressure gas-liquid mixture enters the evaporator, absorbing heat from the circulating water or air and rapidly evaporating, turning into low-pressure gas. At the same time, the temperature of the cooled medium (water or air) decreases. The low-pressure gas after evaporation is then sucked in by the compressor, starting the next refrigeration cycle.