Refrigerant

The task of the refrigerant is to transfer energy from one level and dispose of it at a higher level. There are many different types of primary refrigerants, each with technical substance characteristics, such as pressure, temperature, heat content, specific volume, and entropy for every need.

The use of the different types of refrigerants depends on the size of the systems, but also the production year. In recent years, awareness of the strain on the environment has caused a shift in the use of different refrigerants. As a result, the natural refrigerants are becoming increasingly more popular.

The cyclic process of the refrigerant can be illustrated in a (h) LogP based on the following conditions:

1. The refrigerant is kept under pressure at surrounding temperature as undercooled liquid
2. The refrigerant is expanded to a lower pressure at the point of saturation
3. The heat influence from the media or matter to be cooled causes the refrigerant to boil at the low pressure in the evaporator
4. Once the refrigerant is evaporated into dry, saturated vapour, it is compressed in the compressor to a higher pressure as overheated vapour
5. In the condenser the vapour is condensed under the high pressure by exchanging the energy with e.g. air at a lower temperature than the saturation temperature

Typical types of refrigerants:  

• Synthetic refrigerants type CFC, HCFC, and HFC influence the greenhouse effect.
  For example: R134a, R404A, R407C, R410A, R507A
• Natural refrigerants: R717 (ammonia) R290 (propane), R600a (isobutane), R744 (carbon dioxide)

Refrigerant charge

This is a term used for the type and mass of refrigerant a refrigeration plant will hold to perform under the given conditions. The type of refrigerant must be applicable for the application and the ambient conditions. For example, the ASHRAE standards are general recommendations regarding local ambient conditions for inside and outside temperatures in both summer and winter in any country.

Any refrigerant must be suitable for the application and the ambient conditions, so the performance is energy efficient and reliable. Poorly-chosen refrigerant can lead to instability, inefficient heat exchange, and high-power consumption by the compressor, among other undesired effects.

It is important to know the charge on a refrigeration plant, since refrigerant in almost all countries are subject to environmental control. Almost any refrigeration plant will lose an amount of its refrigerant charge through sealings, stuffing boxes, valves, etc. over time.

It is important to service and overhaul the refrigeration plant. Loss of refrigerant charge will affect the performance, running hours and the reliability of operation.

Secondary refrigerant

Coolant can be divided into primary coolant and secondary coolant. A secondary coolant is generally non-toxic in small amounts, though larger amounts must be disposed of appropriately.

Primary coolant is used in a cooling system to lower the temperature of a secondary coolant, such as brine. The secondary coolant circulates through a cooling system and is cooled in a heat exchanger. The coolant can then be used for other purposes, for example the cooling of ice rinks. A secondary coolant is generally non-toxic in small amounts, though larger amounts must be disposed of appropriately.

Centrifugal pumps from Grundfos are suitable for virtually all applications where cooling is an essential part of the process.