Theoretical analysis of the circuit of a refrigeration machine operating on a zeatropic refrigerant with a large temperature slide for two refrigerant boiling point
Authors: Syazin Ivan Evgenyevich , Gukasyan Aleksandr Valeryevich 
Published: July 2024

When developing new working substances for refrigeration technology, special studies are carried out to identify their properties, which allows to find the most optimal combinations of components and their ratio. By combining different combinations of refrigerant components, its modifications are obtained. Most of the existing refrigerants that have found practical application are mixed. Of the mixed refrigerants, zeatropic refrigerants are distinguished, characterized by separate boiling, that is boiling at lower and higher temperatures (this property is called temperature glide). Zeatropic refrigerants with a temperature glide of more than 7 K are currently not considered promising due to the difficulties encountered during operation and service. But, as you know, something that does not find application in the primary area of use of technology, when a need arises (in this case, the property of having a large temperature glide) can find prospects in some other technical niche, the same applies to refrigeration machines. The presence of a technical solution to transform a disadvantage into an advantage actualizes the use of an object whose use was not considered rational. The design of a refrigeration machine operating on a zeatropic refrigerant with a large temperature glide of two boiling points is considered. This scheme has its advantages and disadvantages, which are discussed in this article. It is important to note that the proposed scheme is not entirely correct to compare with the well-known scheme for two boiling points or a compound scheme due to different principles for obtaining two boiling points and the potential possibility of using the principle used in the scheme to operate on several refrigerants simultaneously. In the proposed scheme, the driving force behind the separation of the refrigerant into two streams in the condenser into “low-boiling” and “high-boiling” components is their difference in saturation temperatures.
BACKGROUND: large temperature glide (difference between the highest and lowest boiling points of the refrigerant components) of zeatropic blended refrigerants is usually considered as a negative factor that limits their application. As it is known, a disadvantage under certain conditions can be turned into an advantage. The use of the temperature glide of a zeatropic mixture makes it possible to separate the refrigerant components to obtain two boiling temperatures, the larger the temperature glide, the greater the difference in boiling temperatures that can be obtained. This will allow to use the refrigeration machine for cooling of products at appropriate temperatures, finally it expands the use of zeatropic refrigerants, simplifies the scheme of refrigeration machines in comparison with analogues using for two boiling temperatures one-component refrigerants or quasi-zeatropic mixed substances.
AIMS: to carry out a theoretical analysis of the practical realization of the scheme of the refrigeration machine operating on a zeatropic mixture with a large temperature glide at two boiling temperatures.
MATERIALS AND METHODS: the method of theoretical development was used, which allowed us to propose and analyze the prospects of the scheme of the refrigeration machine operating on zeatropic refrigerant with temperature glide from 7...10 ℃. Schemes of vapor-compression refrigeration machines served as objects of research.
RESULTS: the scheme of the refrigerating machine for operation on zeatropic refrigerants with obtaining two boiling temperatures due to the temperature glide of 7...10 ℃ has been developed. The result is achieved due to the difference in the saturation temperatures of the components, which allows the separation of the latter on the high pressure side (in the condenser(s), which require a special design) with further directing them to the evaporators with different boiling points.
CONCLUSIONS: studies allow us to conclude that it is theoretically possible to use zeatropic substance for obtaining two boiling temperatures in the scheme of one refrigerating machine by separating the refrigerant components on the high pressure side due to the difference in saturation temperatures. However, the proposed technical solution requires the use of appropriate condensers, the schemes of which were also proposed in this paper.