THERMOPHYSICAL PROPERTIES OF MULTICOMPONENT OZONE-SAFE REFRIGERANTS
Abstract
The paper presents the results of the analysis of the use of multi-component working bodies in throttle cooling systems of an open or closed cycle using the Joule-Thompson effect (cryocoolers). The use of multicomponent refrigerants makes it possible to obtain the required thermodynamic efficiency of the cooling cycle at low throttling pressure values of 1.5...2.0 MPa. This effect becomes possible due to the introduction of components with a higher boiling point into the composition of the working fluid. In order to obtain higher operational characteristics, irreversible losses in J-T cryocoolers must be analyzed and ways of their reduction determined. The thermodynamic analysis of the installation cycle and subsequent design of the heat exchange equipment of cryocoolers formulates the conclusion that in order to optimize the design of the heat exchange equipment of the installation, which consists in solving hydrodynamic and thermal problems, a careful determination of the thermophysical properties of mixed working bodies is necessary. It should be taken into account that the principle of additivity is not always possible to apply for different compositions. By choosing certain components of the working body and changing their mass composition, it is possible to obtain the necessary properties. On the basis of experimental studies conducted at Ltd «DNIPRO MTV», the main components of the refrigerant were determined. When using mixed refrigerants, their thermophysical and calorific properties are determined taking into account the polarity of the molecules and the mass amount of the components of the mixture. Methods for determining thermophysical properties were analyzed, proposed by generalizing dependencies for determining the caloric properties of mixed refrigerants. the main components of the refrigerant are determined, namely: methane CH4, ethylene С2Н4, propane С3Н8 and isobutane С4Н10. The peculiarity of these substances is that they belong to hydrocarbons of the alkane series and are characterized by different values of thermophysical parameters. When calculating the parameters of the throttling and heat exchange processes, it is necessary to determine not only the integral characteristics, but also their values at certain parameters at the characteristic points of the process on the cycle diagram. Therefore, there is a need for obtained generalized dependencies both for individual components and for the mixture as a whole. With a significant number of options for parameters and components of the mixture, when determining the thermophysical properties of refrigerants, it is advisable to use empirical dependencies, where the values of the coefficients are obtained by processing experimental data. Bibl. 15, Fig. 1, Tab. 1.
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