Thermophysical properties of porous materials

2020 ◽  
Vol 7 (4) ◽  
pp. 29-39
Author(s):  
Hanna Koshlak ◽  
◽  
Anatoliy Pavlenko

The study of the porosity of thermal insulation made of refractory materials is an important task for the power industry, since the thermal conductivity of porous materials depends on the shape and especially the location of the pores. An analytical review of existing technologies shows that research in this area is not enough to simulate the process of heat and mass transfer in porous alumina material. Experimental determination of the characteristics of heat and mass transfer in porous materials during the formation of a porous structure is a pressing scientific problem. This article analyzes the influence of the composition of materials on the formation of pores, as well as the effect of various impurities and temperature on the thermal conductivity of the material.

2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Z. A. Burova ◽  
◽  
S.O. Ivanov ◽  
T.O. Roman ◽  
V. P. Vasyliv ◽  
...  

Healthy diet is one of the most important elements in maintaining health and strengthening the nation's immunity, an essential condition for achieving active longevity of present and future generations. Inventing new ingredients and creation of food products based on them, development of new and improvement of existing technologies requires reliable information about the basic thermophysical characteristics of raw materials and biological substances to calculate and optimize heat and mass transfer processes during processing and production. Modern science offers a wide range of studies on the thermodynamic and heat and mass transfer process parameters, determination of the thermophysical characteristics of new substances and products using metrologically certified devices and information measuring systems. The main problem in the study of materials of biological origin is their inhomogeneity and sample structure heterogeneity. Measuring the effective thermal conductivity coefficient of bulk materials and cereals should be carried out in a stationary thermal mode on the device for determination of the thermophysical properties of materials and thermal effects, which implements a symmetrical scheme of the thermometric method of measurement using heat flow and temperature sensors. Using four measuring cells allows synchronous comparative analysis of several samples, and the rotary clamping mechanism helps to minimize contact resistance. The developed technique for measuring the coefficient of effective thermal conductivity takes into account the characteristics of bulk food products and significantly increases the accuracy of their thermal conductivity determination by introducing a correction for the contact resistance of the wall layer. The possibility of long-term observations allows to study thermolabile materials, analyze the thermal effects in the samples, to estimate the volumetric and integral heat dissipation. Calorimetric studies of a wide range of biological materials and substances can be performed with sufficient accuracy by the STA system, which implements step-by-step scanning and synchronous thermal analysis methods to determine the specific heat capacity and heat of evaporation, the ratio of free and bound moisture in heterogeneous materials. These characteristics are integral parameters in the study of the kinetics of heat and mass transfer processes, including drying, for the calculation and design of process equipment. Research on the thermophysical characteristics of heterogeneous materials and substances will optimize production processes and further develop technologies in the food, biotechnology, and processing industries.


1991 ◽  
Vol 113 (3) ◽  
pp. 757-762 ◽  
Author(s):  
Jen Y. Liu

This paper presents an application of the Luikov system of heat and mass transfer equations in dimensionless form to predict the temperature and moisture distributions in a slab of capillary-porous material during drying. The heat and mass potentials of the external medium in the boundary conditions are assumed to vary linearly with time. The method of solution is illustrated by considering the drying of a slab of lumber. Numerical results based on the estimated thermophysical properties of spruce are presented.


2021 ◽  
Vol 2039 (1) ◽  
pp. 012018
Author(s):  
M V Malevany ◽  
D A Konovalov

Abstract The article considers the problems and features of heat and mass exchange on developed surfaces in the conditions of both single-phase and vapour-liquid flow during its condensation. We give a brief analytical review of studies of hydrodynamics and heat exchange in such systems. We analyzed the efficiency of the working channel of the condensation filter and identified problematic points. We offer possible methods for intensifying heat and mass transfer on working surfaces.


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