THE ENGINEERING METHODS FOR DETERMINING THE GEOMETRIC DIMENSIONS OF MULTI-TUBE BI-COOLANT CAPACITORS

B. Pychkov, Т. Kopeykina

ABSTRACT

Artificial cold is widely used in various industries and agriculture, transportation, air conditioning systems and many other fields of science and technology. High-quality equipment for the production of cold is also important for the technical equipment of the Armed Forces, because it is sometimes necessary to provide certain temperature conditions for the reliable operation of electronic means for various purposes and electronic equipment of weapons. In a hot climate, there is a need to create comfortable conditions for the personnel of the units, as well as ensuring quality storage of food and water.

An important device of any refrigeration machine is the condenser of coolant, which significantly determines its efficiency. Recently, much attention is paid to the study and application of mixtures of known refrigerating agents along with single-component substances. It is shown that in certain cases, mixtures of coolants can improve the volumetric and energy parameters of low-temperature installations and obtain this effect without significant structural changes. This is very promising for mobile installations, including military ones, which have to work in various climatic conditions that require adjustment of cooling capacity.

A promising working substance of bi-cooling plants is a binary non-azeotropic mixture of freons-12 and 22. The mode of operation of bi-coolant capacitors differs from the modes of operation of one-component devices, which is explained by the mutual influence of heat and mass transfer processes occurring   together in the boundary vapor layer at the condensation surface and the condensate film. This circumstance makes the strict calculation of the heat exchange surface of capacitors quite difficult.

In such calculations, it is necessary to use data on the thermophysical properties of the mixture in both the steam and liquid phases. However, these data cannot be found in the literature for all promising two-component refrigerants. Data on the vapor-liquid equilibrium of mixtures are also required.

Taking into account the above, in this work, an experimental study process of the condensation of pure freons-12 and 22, as well as their mixtures on a twenty-row sheaf of ribbing tubes, was carried out. The article describes the construction of the experimental capacitor and the method of measurement. The obtained experimental formulas for calculating condensation on single horizontal pipes and on a sheaf of horizontal pipes, as well as on the impact of the rows of condenser pipes on heat transfer are presented. The obtained data are compared with the literature data.

The results of the experiment allowed us to propose a simplified engineering method for calculating the condensation surface of multi-tube bi-coolant capacitors. In addition, a method   for calculating the   basic geometric parameters of such shell-and-tube capacitors in the industrial load range is proposed.

KAYWORDS

Non-azeatropic binary mixture, heat and mass transfer during condensation, condenser, vapor boundary layer, heat transfer coefficient, mixture concentratio, multi-tube capacitor, shell and tube type condenser.

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