Functionality of ago congelo
Usable heat sources
- Industrial waste heat in form of water, steam and thermal oil
- CHP waste heat
- Waste heat from thermal post-combustion
- Solar heat
- Biomass plants and biogas plants
Heat energy in preference to electric energy
For the refrigeration generation, electrically driven compression-type chillers are applied by default. In times of high energy costs, a cost-saving alternative can be offered:
- The absorption chiller powered by waste heat.
- It works according to a principle, which is already known since the early 19th century.
- Since nowadays, the conscious and economical use of energy is also a decisive selection criterion in the area of refrigeration engineering, the absorption chiller powered by waste heat is gaining more and more importance.
Basic principles of thermodynamics
According to the basic laws of thermodynamics, heat moves spontaneously only from a higher to a lower temperature level. Refrigeration systems, however, transport heat from a lower temperature level (cooling application) to a higher one. This process requires the use of energy.
In the absorption chiller, the refrigerant (ammonia) absorbs the heat flow Q0 on the “cold side” at a temperature t0 and evaporates during the process. The refrigerant vapour is absorbed by a liquid solution (aqueous ammonia solution), which has a higher dissolving power than the refrigerant. The heat flow QAbs released during this process needs to be dissipated.
A pump transports the incompressible solution with the refrigerant to the higher pressure level using low energy input.
The refrigerant escapes from the solution by heat supply QH to the boiler (actuator of the process) and is liquefied in the condenser while dissipating heat QC.
The refrigerant and solution cycles are closed by means of relief valves (expansion valve and solution valve). In order to increase energetic efficiency, a solution heat exchanger is installed in the solution cycle.
The refrigerant ammonia has excellent thermodynamic characteristics. Therefore, it is one of the classic refrigerants, which has already been used by Linde in his refrigeration systems and was thus made available for a wide variety of applications. To this day, it has not lost its significance. Despite its toxicity and flammability (within tightly defined limits), the chillers with ammonia as refrigerant are safe according to state-of-the-art technology.
