Modelling of processes in the sorption phase thermo transformers
DOI:
https://doi.org/10.31548/energiya2018.01.145Abstract
The basis of the study of the hydrodynamics of multiphase media is mathematical models. At the same time significant scientific interest is represented by the flow of a multicomponent mixture, one of its constituents of which is condensed.
The purpose of the research is to develop a mathematical model of phase processes in sorption thermal transformers.
The equation of motion and state for the whole medium as a whole, determining the voltage and internal energy, is written in the proposition of a locally thermodynamic equilibrium, where the temperature of the medium can be determined at each point. It is also assumed that the velocity tensor is deformed and determined by the field of barocentric velocities of the mixtures.
It is believed that the effect of the composition of the mixture directly manifests itself through the physical and chemical parameters included in the equation of motion and state (heat capacity, viscosity coefficient, modulus of elasticity, etc.).
One of the important sections of the dynamics of two-phase media in a thermoformer is the kinetics of condensation. Condensation can take place when the partial pressure of the steam of one of the components of the mixture in the expansion process becomes greater than its saturation pressure.
One of the characteristic phenomena that occurs in sorption thermal transformers is the diffusion of the agent.
General patterns of investigated phenomena can be obtained by mathematical modeling.
Taking into account that the characteristic of the degree of stability and instability of systems is entropy, the question of the production of entropy is considered.
Whenever a fluctuation outputs a system from an equilibrium state, irreversible processes return it to an equilibrium state. The system's tendency to reach the extremum of the thermodynamic potential and to remain in this state makes the system sustainable. This is precisely the stability of the equilibrium state of the system associated with the existence of thermodynamic potentials.
Unlike equilibrium systems that go into a state with minimal free energy, nonequilibrium systems can develop unpredictably: their state is not always uniquely determined by macroscopic equations. This is due to the fact that, under the same set of conditions, a nonequilibrium system can pass to different states. The reason for this may be fluctuations, small inhomogeneities, defects or other random factors. To what state will a particular system pass, in the general case it is impossible to predict. The new states thus achieved are often "ordered states" that possess a spatio-temporal organization.
In non-equilibrium systems, the concentration of the concentrations and spatial structures may be the result of diffusion; in the closed system, the same dissipative processes erode the inhomogeneities and lead the system to a homogeneous state.
The problem of entropy production in energy-transforming systems was analyzed by A. Bejan. The obtained results allowed to solve the problem of minimization in heat transfer processes, as well as optimization of economic indicators.
The given method of analysis of sorption processes can be used in the investigation of the phenomena occurring in different types of heat pumps (compression, absorption, and their possible combinations), in sorption accumulators, in porous media. Entropy serves as a measure of the energy efficiency of investigated phenomena.
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