Chiller Compressors

Whether a cooling system air conditions a large commercial building or a small residence, it probably uses the cooling process known as a vapor compression cycle. Without chiller compressors, the vapor compression cycle would not be able to do its job. The compressors pump the refrigerant throughout the system, and it also compress the refrigerant so that it is more effective at absorbing heat.

The four main types of chiller compressors are generally divided into two categories: positive displacement and dynamic. It is not that one category of compressors work better than the other, but rather that both categories of the unit serve specific functions. Positive displacement chiller compressors literally compress the refrigerant, which is in gas form. This makes the refrigerant smaller, but full of more pressure. The result is that positive displacement can pump the refrigerant constantly at a steady speed.

Dynamic chiller compressors do not deliver a constant stream of refrigerant. Instead, dynamic units use a fan-like propeller to increase the pressure of the refrigerant. Reciprocating and scroll compressors fall under the category of positive displacement, while centrifugal compressors are examples of dynamic chiller compressors.

Reciprocating chiller compressors fall under the category of positive displacement compressors. In reciprocating units, a piston moves up and down inside a cylinder. When the piston moves downward, it draws the refrigerant in on top of it. Then, as the piston moves upward, the refrigerant becomes trapped and compressed. Eventually the compressed refrigerant breaks free from the cylinder, but it remains compressed. The advantages of reciprocating include low-cost, efficiency, and simplicity; however, reciprocating can only function in small-scale operations.

Scroll chiller compressors also fit into the category of positive displacement compressors. The mechanics of scroll units are pretty similar to the reciprocating. Instead of pistons, scroll use rotors, but the refrigerant still gets trapped and compressed. Scroll have an advantage because of their low-maintenance reputation, reliability, small size, and ability to function quietly. On the downside, they tend to cost more than some of the other types of units.

Centrifugal chiller compressors are an example of dynamic compressors. Inside centrifugal, a rotating fan-like propeller attracts the refrigerant, then traps it and compresses it. Centrifugal are mostly used for large-scale operations because they are the most efficient option in this category. Usually centrifugal run on electric motors, but can also function with gas engines or steam turbines. One of the major drawbacks of centrifugal is that they do not function well at a low-capacity rate.