A refrigeration system is composed of several components that allow it to function. One of the most important components is the compressor which controls the regulation of refrigerant through the unit. When compressors function, they allow for food to be kept at safe cooling temperatures until ready for use. There are several types of compressors used for different refrigeration systems, from units in the home to large-scale manufacturing environments.
Compressors manage the distribution of refrigerant, absorbing energy from cold areas and transferring it to warmer areas within the unit. Compressors alter refrigerant from low-pressure to high-pressure vapor, alternating cooling using a two stage system to keep cool items maintained at one temperature while keeping frozen items kept in the high pressure area. Compressors are classified as either open or sealed. Open compressors are used for large applications like those kept in manufacturing facilities and possess an external electric motor or engine. Hermetically sealed compressors are enclosed within the unit which is ideal for household appliances. Compressors are categorized as dynamic or positive displacement systems with four primary compressor types.
Centrifugal compressors fall within the dynamic category of refrigerator compressors. When operating at full capacity, these compressors are very efficient, pressuring refrigerant vapor from a single or series of impellers. Centrifugal compressors can alternatively be controlled by bypassing hot gas from one port to the other, though this process is considered the inefficient way to operate a unit of this size. A large unit of this type can be controlled through speed control, variable pitch or suction dampers. This compressor is not a common system, but serves a purpose managing a large application in an industrial setting.
The screw compressor falls in the positive displacement category of compressor units, passing refrigerant through screw spindles while compressing the intake of gas. Commonly used in food manufacturing environments, screw compressors usually have one or two spindles and are distinguished as either single-screw or twin-screw compressor types. Twin-screw compressors have two grooved rotors that suck and compress refrigerant through the system. The advantage of screw compressors have the advantage of handling large amounts of refrigerant compared to the other compressors in the positive displacement category. They can compete with low-capacity centrifugal compressors and are available for a variety of applications. Another advantage of screw compressors is their stability, avoiding some of the vibration problems of other systems.
Scroll compressors also fall in the positive displacement category and are considered a generally efficient compressor type and the most common compressor on the refrigeration market. In a scroll compressor unit, an electric motor driven scroll meshes with a stationary scroll forming pockets that trap, transport and compress low pressure refrigerant from the outside of the scrolls to the discharge passage. The scroll compressor is noted for its smooth and continuous compression performance, lower leakage rates and efficiency.
Piston or Reciprocating Compressors
The final type of unit in the positive displacement category is the piston or reciprocating compressor. Commonly used for commercial purposes in manufacturing environments, the reciprocating compressor is similar to an automobile engine in its composition. Using a motor to suck in and then compress refrigerant in a cylinder, the unit uses the piston to initiate the process, allowing an intake valve to open and close when the appropriate pressure level has been achieved to cool the refrigeration unit. The intake and exhaust valves are designed so refrigerant flow travels in one direction through the system.