Innovations of the 21st century in refrigeration technology have affected the areas of deep cooling (below - 40 ºС) and especially the air conditioning (above +7 ºС): highly efficient machines have been created that meet the most stringent requirements. At the same time, the most important temperature range in refrigeration engineering (from +4 to -40 ºС) remained unchanged (expect invention of invertors for cooling) for almost 100 years: the main share of this interval is occupied by single-stage chillers that “do their job well”. In its lower part (interval), two-stage refrigerators are also used, due to slightly higher efficiency in the low-temperature region. All that has been tried so far is to improve electronic control systems. This gave a certain effect, which was leveled after the transition to environmentally friendly refrigerant composites having a lower COP (Coefficient of Performance) compared with the old ones.
The principle of organizing a multi-cascade refrigeration system that we created was a breakthrough in the field of increasing the energy efficiency of refrigeration cycles for commercial temperatures. Depending on the season and the operating temperature in the refrigerator, the energy savings can be up to 40% (!!!). This is especially true for countries with a hot climate, but in a temperate climate, savings can be significant, especially with the massive use of the new principle.
The concept of building a cascade was changed: in contrast to the classic cascade refrigeration machines aimed at obtaining ultra-low temperatures, the goal was to increase the COP of the refrigeration unit. One of the important points was the understanding that classic single-stage chillers were created for old refrigerants. For many years, none of the researchers thought that replacing refrigerants requires rethinking the operation of the entire refrigeration cycle. What has been described in the literature relates to old systems, and is not very compatible with new ones. The task was realized by redistributing the functional capabilities of individual elements of the system, taking into account the altered thermophysical properties of the latest refrigerants.
The most important thing is that the versatility of the multi-cascade has been achieved: it can be used both in stationary installations and in mobile ones, both in new and for improving the performance of old ones. High reliability of the system, increased refrigeration capacity and service life, a positive impact on the environment, especially when using a multi-cascade in mobile refrigeration units. Structural flexibility occupies a special place: the ability to include additional branches (for example, an adsorption branch using minimal (and even uneven in time) sources of waste heat), which give an increase in savings.
Ideally, all refrigerators used in the commercial temperature range (from +4 to -40 ºС) should be cascaded. As well, saving resources and reducing the carbon footprint are huge.