International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

To design energy-efficient buildings, it is essential to accurately calculate, monitor, and analyze their energy consumption at all stages: from conceptual (sketch) development and design to construction and operation. However, current regulatory documentation lacks methodologies that fully account for the interrelated processes occurring in building envelopes—such as heat transfer, moisture accumulation, and air infiltration—evaluate the effectiveness of specific energy-saving measures, or perform energy consumption data analysis to determine a building’s actual energy performance indicators.This highlights the relevance of calculating and analyzing building energy consumption while accounting for heat and mass transfer processes in envelope structures and the presence of various architectural and construction elements. A methodology has been developed for processing data obtained from building thermal energy metering systems. This methodology allows, during the operational phase, to determine buildings’ energy characteristics, evaluate the efficiency of thermal energy use, and assess the effectiveness of energy-saving measures.

Calculation of thermal diffusion and filtration fluxes at the interface by “traditional” methods requires preliminary determination of the potential values (concentration, moisture content, temperature, pressure) in the four-dimensional space of events. Such methods for solving boundary value problems, which provide “extra” information for technical calculations, are usually very laborous and require the use of numerical methods that are not always convenient in engineering practice. The proposed fieldless calculation method allows one to determine on the boundary of the region the gradients from the transfer potentials and, consequently, energy and material flows in the form of a known functional of the potentials at the interface at their short-term contact directly on the matrix of transfer coefficients of the formalized boundary value problem. This method uses the fractional index differentiation operation (fractional differentiation) and is convenient for solving limiting boundary value problems, i.e. when the characteristic size of the contacting phases in the boundary conditions of boundary value problems tends to infinity or the time of their interaction tends to zero.

Using the methods of systemic, mathematical and numerical analysis, as well as general physicochemical and thermodynamic laws, a complex of theoretical and experimental studies of transfer processes during short-term contact of phases has been carried out. These studies made it possible to fully reveal the regularities of external and internal heat and mass transfer, to find scientifically grounded ways to intensify the processes of vacuum, conductive and combined drying methods. Within the framework of linear nonequilibrium thermodynamics, a mathematical model of filtration-diffusion energy and mass transfer has been developed with a correct estimate of the orders of the terms in the system of differential equations of energy and mass transfer, taking into account the composition of the vapor-air mixture in the capillary-porous body. The limits of applicability of the hypothesis of short-term contact of phases according to the Fourier criterion for the transfer inside and outside the surfaces of the canonical shape (plate, cylinder, sphere) and wedge are estimated from the standpoint of the accuracy of calculating interphase flows. It is shown that in a number of cases the contact is not short-lived due to the curvature and the presence of angles on the contact surface, and not due to the finiteness of the dimensions of the contacting phases.

Modern intensification of materials processing technology leads to an increase in the role of non-stationary interconnected exchange processes compared to stationary unconnected interconnected exchange processes compared to stationary unconnected. This fact is still insufficiently reflected in the field of solving energy and mass transfer problems (EMT) at small Fourier numbers (Fourier numbers ≤0.1) at short-term phase contact (SPC). In this article, a generalized mathematical model of interconnected non-stationary irregular energy and mass transfer mode at short-term contact across a boundary with selective permeability of phases is formalized. In vector-matrix form, a conjugate mixed boundary value problem is solved with excitation in each of the phases of flows of substances absent in the other phase. By analogy with heat exchange and mass exchange, matrices of potential assimilation of phases and a contact matrix are introduced, which allows obtaining a uniform solution for a number of special cases and especially simplified the entry for the vector of interphase flow densities. The mathematical notation of the solutions of the considered parabolic system of partial differential equations of the second order for intensive irreversible processes (Fourier numbers ≤0.1) are written in vector-matrix form and are close to the scalar Higbee theory for mass transfer.

The paper considers an analytical method for solving systems of equations of conjugate non-stationary heat and mass transfer with account of volumetric negative or positive heat sources (and steam generation aswell). The obtained data can be used to find integral kinetic dependencies of heat and mass exchange processes, analytical formulas for calculating heat and mass transfer coefficients and other derivative quantities necessary for engineering calculations of processes and devices in chemical technology, biotechnology, industrial heat power engineeringand other industries.