Pumps for refrigeration (or refrigeration pumps) are pumps that are employed for cooling purposes. They transfer heat from a cooler region to a warmer region using the refrigeration cycle. Refrigeration pumps force thermal energy to flow in a direction opposite its natural direction. Heat flows from a warmer region (one of higher temperature) to a cooler region (one of lower temperature) without the application of an external power or pump.
The refrigeration pump works as a compressor that moves a refrigerant (cooling fluid) through the cooling system. Refrigeration pumps perform a key function in the refrigeration cycle.
Refrigeration pumps are often employed in liquid-overfeed and transfer-pump systems which make use of anhydrous ammonia, aqueous ammonia, and other refrigerants like R22: chlorodifluoromethane (CHClF2).
There are several types of refrigeration pumps. They are classified into: centrifugal pumps, reciprocating pumps, rotary pumps, and screw pumps.
Centrifugal refrigeration pumps comprise the impeller or the blower. They can handle large quantities of refrigerants. One of the most popular centrifugal refrigeration pumps is the open-drive refrigeration pumps. They have been employed in industrial cooling processes for decades. These pumps are used in cold storage, food processing, refrigeration, ice production and turbine inlet cooling. They are also used as liquid overfeed and transfer systems; hence they utilize refrigerants such as anhydrous ammonia, aqueous ammonia and halocarbons such as R22.
Reciprocating refrigeration pumps are popularly used refrigerating pumps. They utilize a piston and cylinder in their design like an automobile engine. There are three types of reciprocating pumps: hermetically sealed, semi-hermetically sealed and open type. The open-type reciprocating pumps are either single or multi-cylinder type.
Rotary refrigeration pumps have two rotating elements, like gears, between which the refrigerant is compressed. They are particularly useful in pumping refrigerants at low or moderate pressures. Because of this they are not as widely used as reciprocating or centrifugal pumps.
Screw pumps comprise the pair of meshing screws between which the refrigerant gets compressed. They are effective with a wide range of refrigerants and are able to pump at high pressures for small quantities of refrigerants. They are quite efficient and consume less power than the reciprocating pumps and hence are widely used.
As with all systems, proper maintenance of refrigeration pumps are necessary for efficient functioning and longevity. To maintain pumps, terminals should be inspected, connections should be tightened and cleaned, motors should be lubricated, and belts should be inspected for tightness and wear. To all relevant terminals and parts, non-conductive coating should be applied. The electric controls should be checked to ensure optimal functioning. Thermostat operations should also be regularly checked. All of these ensure that the cycle of cooling and heating required for the pump to work run as they should.
Using refrigeration pumps has its advantages and disadvantages. The main disadvantages are that they are difficult to install and may give problems in cold weather. The advantages, however, make up for these. They have low running costs. They require minimal maintenance, and are generally safe, long-lasting and eco-friendly.