USING THE UNIVERSITY'S ENERGY EFFICIENCY KNOWLEDGE HUB FOR ENERGY RENOVATION AND ENERGY MODERNIZATION OF UNIVERSITY BUILDINGS

BACKGROUND AND OBJECTIVES. The most important socio-economic task in the current period is to transfer Ukraine's economy to an intensive way of development in order to improve the level and quality of life of the population and solve the full range of social problems. Implementation of such a policy dictates the need to solve problems of reconstruction and modernization of buildings and structures, primarily related to the public sphere (including higher education institutions), in order to eliminate the existing inconsistency of the technical condition and functional and consumer qualities of public buildings to current standards and consumer requirements. Therefore, one of the most urgent directions of development of higher educational institutions is the task of providing effective overhaul and reconstruction of buildings, increasing their energy efficiency.METHODS. The theoretical and methodological basis of the study were the fundamental and applied developments of leading domestic and foreign scientists in the theory and practice of management of energy modernization and energy reconstruction of buildings, increasing energy efficiency of buildings. The factual basis of research were the legislative acts of Ukraine in the field of energy efficiency, normative and methodical documents on the modernization and reconstruction of buildings, Directive 2010/31/EC in the field of energy saving. When solving specific tasks the methods of system and comparative analysis, economic-mathematical methods of efficiency evaluation of energy reconstruction and energy modernization projects were used.FINDINGS. The method of calculation of the reduced resistance to heat transfer of the enclosing structures and the shell of the 4th building of Kyiv National University of Technology and Design as a whole taking into account the temperature and humidity conditions in the fencing marginal zones. It is shown that in the enclosure edge zones the heat protective properties decrease resulting in a deterioration of the heat protection of the whole building. Practical recommendations for the design of fencing structures of modern buildings taking into account the temperature-moisture regime are proposed.CONCLUSION. For the analysis of complex processes of moisture transfer in enclosures, a mathematical model based on the moisture potential is most convenient. A certain difference from the thermal potential (temperature) to the definition of the moisture potential allows to diagnose the most general assessment of the moisture regime of exterior and interior fences on the basis of HUB knowledge on energy efficiency. At use of this model it is possible to consider process of moisture exchange in a wide range of humidity and temperature taking into account movement of a moisture as a basis of carrying out energy reconstruction and energy modernization of operating buildings of the university.

A Model for Assessment of Heat and Moisture Transfer Hollow a Hemp Concerte Wall Using Finite Element Method

The energy performance of buildings represents a major challenge in terms of sustainable development. The buildings and buildings construction sectors combined are responsible for over one-third of global final energy consumption and nearly 40% of total direct and indirect CO2 emissions. In order to reduce the energy consumption of buildings and their harmful impact on the environment, special attention has been paid in recent years to the use of bio-based materials. In the present paper, a model of heat and moisture transfer hollow hemp concrete wall is proposed using finite element method. The energy and mass balances are expressed using measurable transfer drivers as temperature water content and vapor pressure and coefficients related explicitly to the macroscopic properties of material as thermal conductivity, specific heat, and water vapor permeability. The proposed model is implemented in MATLAB code and validated through experimental measurements.

Heat and moisture transfer kinetics and temperature during drying of fabrics

The methods of approximation of the curve of the drying rate of fabrics according to the methods of A. V. Lykov and V. V. Krasnikov are described. The results of processing experimental data on convective tissue drying are presented. Equations are given for determining the drying time of fabrics, the density of heat flows and the temperature of fabrics during the drying process. The equations for determining the drying coefficient and the relative drying rate are given. An analytical method for determining the temperature for the period of falling drying rate is considered. The comparison of the temperature values according to the results of analytical solutions with the values obtained by the experimental formula is given. It is shown that the number of Bio during drying of fabrics is less than one, and the main limiting factor is the external heat and moisture exchange of the evaporation surface from the surface of the material with the environment. Verification of the reliability of the calculated values obtained with experimental ones is presented. The discrepancy between the values is within 5 % of the accuracy of the experiment and processing.

DERIVATION OF THE EQUATION OF UNSTEADY-STATE MOISTURE BEHAVIOUR IN THE ENCLOSING STRUCTURES OF BUILDINGS USING A DISCRETE-CONTINUOUS APPROACH

Two differential equations of moisture transfer based on the theory of moisture potential have been considered. The first equation includes the record of moisture transfer mechanisms of vapor and liquid phases and their relationship. The second equation is a simplified form of the first equation which makes it possible to apply a discrete-continuous approach. The peculiar properties of the boundary conditions setting of the outside air for temperature and humidity fields have been presented. It is proved that the use of the discrete-continuous method provides high accuracy of calculations and can be used in engineering practice to assess the unsteady humidity regime of enclosing structures.

Use of different criteria for estimating precocity of heterosis maize hybrids in forest-steppe conditions

In the article it is shown the results of the study of heterosis hybrids of corn on the signs of early ripening, such as: the growing season, the number of leaves on the main stem, the moisture yield of grain during harvest. To distribute our corn material by precocity, a number of studies were conducted, namely: estimating the length of the growing season "shoots – full ripeness", which was determined in days, and a very important indicator today is the moisture content of grain when harvested in percentage, it allowed to distribute heterosis hybrids into two groups: early-maturing (106–114) and middle-early – 114–123 days. Over the years of testing, the weather conditions varied considerably, which made it possible to evaluate in detail the material under study. In 2020, the growing season was within 107.8 days, which is almost three days less than in 2021. At the same time, the longer vegetation period was in 2021. Therefore, the aim of our study was to analyze the rate of moisture yield of corn grain of the studied hybrids of the two maturity groups. The conducted researches allowed to trace the dynamics of grain moisture yield of early-maturing maize hybrids and one hybrid of the middle-ripening group of maturity, to determine the variability of hybrid grain moisture in different periods of grain maturation. The year 2021 was more favorable for growing corn, the plants formed a large vegetative mass, but the grain had a high humidity during the harvest period. This is due to a significant amount of precipitation (69.9 mm) in August 2021. Hybrids that had high harvest humidity were characterized by a long growing season, such as № 47 × № 33. Therefore, our selected hybrids can be successfully used in planning a strategy for early maturity. In establishing the patterns of moisture transfer of grain when it reaches, in particular, the influence of the conditions of the year, in our study group were identified two hybrids consistently better in terms of grain moisture. Preference should be given to hybrids № 31 × № 37 and № 83 × № 125, which combine indicators of early maturity: the shortest growing season, the number of leaves on the main stem and the rate of moisture.

Comfort-Related Properies of Cotton Seersucker Fabrics

This work concerns the comfort-related properties of seersucker woven fabrics made of cotton. Seersucker woven fabrics are characterized by alternating puckered and flat strips in the warp direction. Some researchers consider that due to this structure seersucker fabrics are characterized by very good comfort-related properties. In this work seersucker fabrics with differing repeats of the seersucker effect and different weft yarns were investigated in intense heat and high moisture transfer. Results showed that the structural factors significantly influence the comfort-related properties of the investigated cotton fabrics.

Evaluation of a Moisture Diffusion Model for Analyzing the Convective Drying Kinetics of Lavandula x allardii Leaves

In the present case study, a moisture diffusion model is developed to simulate the drying kinetics of Lavandula x allardii leaves for non-stationary convective drying regimes. Increasing temperature profiles are applied over the drying duration and the influence of temperature advancing rates on the moisture removal and the drying rate is investigated. The model assumes a one-dimensional moisture transfer under transient conditions, which occurs from the leaf center to the surface by liquid diffusion due to the concentration gradient developed by the surface water evaporation caused by the difference of water vapor partial pressure between the drying medium and the leaf surface. A numerical solution of Fick’s 2nd law is obtained by an in-house code using the finite volume method, including shrinkage and a variable temperature-dependent effective moisture diffusion coefficient. The numerical results have been validated against experimental data for selected cases using statistical indices and the predicted dehydration curves presented a good agreement for the higher temperature advancing rates. The examined modeling approach was found stable and can output, in a computationally efficient way, the temporal changes of moisture and drying rate. Thus, the present model could be used for engineering applications involving the design, optimization and development of drying equipment and drying schedules for the examined type of non-stationary drying patterns.

The use of sorption and excess sorption isotherm in the mathematical modeling of the unsteady-state heat and humidity regime of the building envelope

In the given article the development of the moisture transfer equation based on the theory of moisture potential is considered. The task of combined heat and moisture transfer is one of the most complicated tasks in the building thermal physics field. The classical equations of moisture transfer by K.F. Fokin representing the transfer of moisture under the action of partial transfer potentials - the gradient of the partial pressure of water vapor and the gradient of humidity F - are listed. The possibility of uniform accounting of the combined water vapor transfer on the basis of the moisture potential F is described. The sorption isotherm for aerated concrete is constructed in accordance with the experiment carried out in a desiccator with an aqueous solution of sulfuric acid. A new equation of moisture transfer which takes into account moistening with vaporous moisture in the sorption zone of moisture and liquid moisture in the excess sorption zone of moisture is derived. In order to simplify the work with the obtained equation a new value of the relative potential capacity is introduced. A graph construction of sorption and excess sorption isotherms which are obtained using an analytical expression for the relative potential capacity is proposed. In the sorption zone of humidification the sorption and excess sorption isotherms coincide with the classical sorption isotherm. Meanwhile, in the excess sorption zone of humidification the sorption and excess sorption isotherms depend on temperature.