At the industrial level, two types of refrigeration cycles are employed: the industrial absorption refrigeration cycle and the industrial compression refrigeration cycle. Both cycles originated and developed in the 19th century. However, the compression cycle prevailed over absorption in the early 20th century, although the absorption cycle never disappeared. Currently, the absorption cycle is regaining its industrial presence thanks to its significant advantages.
Industrial Compression Refrigeration Cycle
The industrial compression refrigeration cycle is accomplished by circulating refrigerant through the four main components that make up the refrigeration system. In other words, refrigerant is circulated through the compressor, condenser, expansion valve, and evaporator.
Through these components of the industrial refrigeration system, the refrigerant gas undergoes a continuous thermodynamic cycle. This thermodynamic cycle allows for the extraction of heat from a refrigeration chamber and its dissipation to the exterior. In this way, products stored in the refrigeration chamber are cooled for long-term preservation.
The compressor is a machine driven by an electric motor or a combustion engine. The compressor’s function is to compress the refrigerant gas (NH3, CO2, HFC, etc.) to a specific working pressure. With this pressure, the refrigerant can circulate through the rest of the refrigeration system. There are various types of compressors that can perform refrigerant compression, including piston reciprocating compressors, screw compressors, and scroll compressors.
This component of the industrial refrigeration system receives the high-pressure and high-temperature refrigerant gas exiting the compressor. The condenser’s role is to dissipate a significant portion of the temperature of this gaseous refrigerant to the external environment.
In other words, the condenser is a heat exchanger. As the refrigerant loses temperature, it changes into a liquid state at the condenser’s outlet. This cooling and change of state are essential for the proper functioning of the system.
The expansion valve receives the high-pressure liquid refrigerant exiting the condenser. Using a small orifice, allows the refrigerant to pass through at much lower pressure. Consequently, the liquid refrigerant exits the valve very cold.
The evaporator is a heat exchanger located inside the refrigeration chamber, which receives the refrigerant exiting the expansion valve. Since the refrigerant is very cold, the evaporator absorbs heat from the interior of the refrigeration chamber.
This heat absorption causes the refrigerant to change into a gaseous state at the evaporator’s outlet. Then, this gaseous refrigerant enters the compressor’s suction line. This way, the industrial refrigeration cycle that starts at the compressor concludes at the evaporator’s outlet.
Industrial Absorption Refrigeration Cycle
The main difference between the industrial absorption refrigeration cycle and the compression cycle is that the former does not use a compressor. The other components of the industrial absorption refrigeration system are essentially the same: condenser, expansion valve, and evaporator. The industrial absorption refrigeration system employs two substances: the refrigerant and the absorbent.
In practice, the most commonly used substances are water-lithium bromide and ammonia (NH3)-water. When using water-lithium bromide, water serves as the refrigerant, and lithium bromide serves as the absorbent. On the other hand, if NH3 water is used, NH3 is the refrigerant, and water is the absorbent. Water and lithium bromide are used in absorption systems with working temperatures above 0°C.
However, for temperatures below 0°C, ammonia and water are employed. Absorption systems have an average energy efficiency of 0.8, while compression systems achieve higher efficiency (3 to 4). For this reason, absorption systems are used when there is a significant amount of residual thermal energy available from another industrial process. Below, we explain what their main components are and how they function, except for the condenser, expansion valve, and evaporator, which were explained earlier.
The thermal generator is essentially a container containing the refrigerant-absorbent solution. This container receives thermal energy (heat) from the outside to produce the separation of the refrigerant through its evaporation. Subsequently, this gaseous refrigerant, at high pressure and temperature, enters the system’s condenser to release heat to the environment and change into a liquid state.
As you can see, the thermal generator creates the same conditions that the compressor produces, as explained earlier. This initiates the industrial absorption refrigeration cycle in a manner similar to how the compression cycle was described earlier.
The refrigerant absorber is a container that contains the absorbent substance (water or lithium bromide). When the refrigerant exits the evaporator, having passed through the condenser and expansion valve, it is directed to the absorber. The refrigeration cycle by absorption culminates in the refrigerant absorber, as the absorbent substance once again traps all the refrigerant.
Normally, using a pump and a set of pipes between the absorber and the thermal generator, a portion of the refrigerant-absorbent solution can be transferred. This maintains the continuity of the refrigeration cycle.
Intersam, a specialist company in industrial condensers and evaporators
The condenser and evaporator of an industrial refrigeration system are two very important components. If these components do not transfer heat adequately, the refrigeration system will not function or will not be efficient.
In this regard, at Intersam, we specialize in the design, manufacturing, and installation of high-efficiency condensers and evaporators for refrigerants such as NH3, CO2, HFC, etc. We comply with all technical and safety specifications to ensure that the industrial refrigeration cycle is efficient and faultless.