Refrigeration compressors and vacuum pumps: Essential components for efficient working’

Refrigeration compressors are a special type of compressors that are used for refrigeration, heat pumping, and air conditioning. These are large mechanical units which are specially designed for industrial use unlike small, portable compressors. Refrigeration compressors (also known as refrigerant compressors) are widely used in large scale facilities and equipment. Unlike refrigeration compressors, air conditioning compressors cannot be used for heating or ventilation purposes.

Compressors are one of the most important parts of the refrigeration cycle. They are designed to turn low-pressure gases into high-pressure and high-temperature gases. In technical terms, refrigeration compressors draw vaporised refrigerant from the evaporator at a relatively low pressure, compress it, and then discharge it to the condenser, where it gets cooled. The refrigerant then moves to the expansion valve and the evaporator.

A valve is a device that regulates the flow of fluid by opening, closing, or partially obstructing various passageways. Technically, valves are pipe fittings. Refrigeration compressors make use of pneumatic valves because pneumatic valves share a common reservoir of pressure and retain a more static level of force which helps in controlling the valve effectively without any attendant peak lift load increase. Thus, pneumatic valves help in the efficient functioning of the refrigeration compressors. The technology used in pneumatic valves is getting better every day.

As soon as the refrigerant moves to the pneumatic valves, it finally gets sucked by the compressor again. Thus, it can be seen that a refrigerant must get compressed to the pressure corresponding to the saturation temperature higher than the temperature of the naturally available air or water for the proper functioning of the refrigeration cycle.

Types of Refrigeration Compressors

There are various types of compressors used in the refrigeration and air conditioning machines. Some of the refrigeration compressors are reciprocating, rotary, screw, centrifugal and scroll. All these have been described below briefly:

Reciprocating Compressors (Piston Compressors): The reciprocating compressors are one of the most widely used refrigerating compressors, specially designed for commercial and industrial application. They feature a piston and cylinder arrangement like the automotive engine. The refrigerant inside the cylinder gets compressed by the reciprocating motion of the piston. These compressors are capable of compressing gases to high pressures and support continuous operation. There are three types of reciprocating compressors: hermetically sealed, semi-hermetically sealed and open type.

Screw Compressors: These compressors have a pair of meshing screws between which the refrigerant gets compressed. They can produce high pressure for even smaller quantity of gas. They pass refrigerant vapour through screw spindles which compress the gas. In any standard screw compressor, there are two screw spindles. However, compressors with three or more screw spindles have also been introduced in the market.

Scroll Compressors: The most common type of refrigerant compressors is scroll compressors. The scroll compressor comprises two interleaved scrolls. One of these scrolls is fixed and the other orbits eccentrically without rotating. And the refrigerant gets compressed in the small gaps which are created during its motion. These compressors are widely in use as they have a relatively low rate of leakage and provide high efficiency.

Rotary Compressors: Rotary compressors feature two rotating elements, like gears, between which the refrigerant is compressed. These compressors can pump the refrigerant to lower or moderate condensing pressures and thus are able to handle small volume of the gas and produce lesser pressure.

Centrifugal Compressors: These compressors possess impellers or the blowers that can handle large quantities of gas.

Refrigeration compressors are large modules aimed at refrigeration, heat pumping and air conditioning of large facilities and should not be confused with small, stand-alone compressors. According to industry experts, selection of refrigeration compressors requires a thorough analysis of refrigerant options and nominal cooling specifications. Capacity, input power, condensing temperature, and evaporative temperature are the four basic nominal cooling specifications that one should consider.   

Capacity of a refrigerant compressor measures its ability to remove heat from the refrigerant gas. In most cases, you would find that nominal capacity ratings are based on a standard set of conditions, including condensing temperature (CT), evaporative temperature (ET), refrigerant, and motor revolutions per minute (rpm). It is important to note that refrigeration compressors would have different cooling capacities as the values for these parameters change. One‘s purchase decision would also depend on the power source specifications of these compressors. Power source specifications include voltage, frequency and phase. So, several factors need to be taken into account before you make your final choice. This would help you choose the right refrigeration compressor that would suit your requirements.

In addition to compressors, industrial facilities also require vacuum pumps to isolate and compress air. Industrial vacuum pumps comprise devices such as pistons, claws, scrolling spirals, and diaphragms. There are many industrial units which require vacuum pumps to carry out some or other type of task. For example, many industrial facilities that manufacture vacuum tubes and semiconductors make use of vacuum pumps. High and ultrahigh vacuum pumps are also available for high vacuum regions and to develop molecular flow for highly evacuated systems for optimum operational efficiency.

Air compressors and vacuum pumps are required in many industries and commercial establishments for their efficient functioning. However, the type and size depends upon the nature of work being undertaken.