Experimental study of liquid evaporation from gel mixture surface was performed. Gels based on agarose and starch were studied. Dependencies of liquid evaporation from time were obtained for mixtures of agarose and starch. A non-linear dependency of evaporation speed was observed for all sets of mixtures. It was shown that presence of starch inhibits the process of liquid evaporation.
Unsteady heat transfer in agarose gels of various concentrations was studied in order to make a breakthrough in the technology of 3-D additive bioprinting. Data on the kinetics of the phase transformation was obtained using spectroscopy as a function of temperature during the formation of agarose hydrogel. The dynamics of aging was investigated for gels of different densities. The time dependence of the structural changes was obtained. Particular attention was paid to the changes in the structure of the gel due to the processes of evaporation of the liquid during the gel formation and during long-term storage. Experiments were performed to determine the dynamics of the temperature fields simultaneously with heat flux measurements during the formation of agarose gels from different initial concentrations. A technique based on experimental data for the computations of the thermophysical coefficients of agarose gels was developed.
The paper presents new results on the study of thermokinetics of gel system based on agarose in the process of transition from solution to gel and opposite. This issue is extremely relevant, since the stability and predictability of thermophysical and rheological properties in such transformations, especially in the presence of components of the nutrient medium and immobilized microorganisms, come to the fore in terms of design and selection of modes of operation of the printing device promising 3-D bioprinters, as well as the system of preparation and storage of the presence of the hysteresis effect, both from the point of view of the kinetics of gel formation and from the point of view of the dependence of rheological properties on temperature, at different concentrations of modifying components, is shown. The obtained results allow to draw a conclusion about the possibility of using the scheme with preliminary preparation of the initial biogel for the implementation of bioprinting technology based on agarose, and to recommend the obtained values for modeling the operating modes of devices of this type.
The same properties of agarose gels containing neutral bioresorbable additives and living microorganisms which are important for use in additive technologies of bioreactors creation were considered. Data on the kinetics of gel formation from the solution during cooling were obtained by spectroscopic measurement by measuring the shift of the maximum spectrum of light passing through the gel, depending on the temperature. The dynamics of aging was investigated for gels of different concentrations of agarose, bioresorbable additives and living cells. The time dependences of the decrease in the optical transparency of such gels during the aging process, characterizing the changes in their structure, were obtained. Special attention was paid to the effect of liquid evaporation from gels in the process of gel formation and during long-term storage on relaxation processes leading to their spontaneous increase in density. Experiments were performed to determine the dynamics of the temperature fields simultaneously with heat flux measurements during the formation of studied gels with different concentrations. On the basis of the obtained experimental data and previously developed method, the thermophysical coefficients of agarose gels containing an admixture of starch and living yeast cells were calculated.
Theoretical and experimental study of acoustic velocity in vapor-liquid mixture that contained close-packed layer of spherical particles was performed with respect to non-stationary heat transfer between mixture and particles in compression half-wave. Theoretical model allows to explain the decay of equilibrium acoustic velocity compared to its adiabatic value in case of increasing of void fraction in the mixture. Calculated results are in agreement with experimental data, obtained in vertical channel with vapor-liquid filtration with close-packed layer of spherical particles of borosilicate glass, steel, and lead. Key words: vapor-liquid mixture, layer of spherical particles, the equilibrium acoustic velocity, non-stationary heat transfer Pokusaev, B. G., et al.: Equilibrium Acoustic Velocity in Vapor-Liquid .
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