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3 Journal of New Technologies in Environmental Science

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Influence of structural characteristics of porous materials on the coefficient of thermal conductivity

100%

Cheilytko A.

tom Vol. 6, nr 3

104--112

The existing dependences of the effective coefficient of thermal conductivity of the material depending on the size and location of pores in it are analyzed and compared with each other and with previously obtained experimental data. It is shown that the resulting thermophysical properties of the material are affected not only by the porosity, but also by the location of the pores in the volume of the material. The disadvantages of the existing dependences of determining the effective thermal conductivity of the material on the type of porosity (both for porous material and for dispersed systems) are shown. Also, the most reliable dependences of the thermal conductivity coefficients on the porosity of dispersed systems for backfill materials and the need for their correction by empirical coefficients are determined. Complex indicators that fully describe the porous structure and on which the mathematical model of heat exchange processes in a porous medium should be based are proposed.

Research of the question of increase of efficiency of cooling of the power equipment of hydroelectric power plants

63%

Cheilytko A. , Ilin S.

tom Vol. 4, nr 1

22--29

Improving the cooling efficiency of power transformer windings with a cross-sectional width of the radial channel less than 3 mm, by improving the geometric parameters of the cooling system while reducing the material consumption of the electric machine is an important area of research. Excess oil pressure in the winding channels increases with increasing serial number of the coil. It was found that with increasing oil velocity at the inlet to the horizontal channel, the values of excess pressure in it increase in quadratic degree. It is established that a lifting force occurs in the oil of the horizontal channel, as evidenced by the increase in excess pressure near the upper boundary of the channel. For the first time, an analytical dependence of the excess oil pressure in the radial channel of the disk winding of the power transformer on the oil flow rate at the inlet to this channel was obtained. The dependences of the excess pressure in horizontal channels with a cross-sectional width of 1 mm on the velocity of oil at the inlet to this channel were obtained, which allows to calculate the speed by which it is possible to organize through circulation of oil in the channel provided that excessive pressure in the channel is prevented. situations. A new mathematical model of interconnected heat exchange and hydrodynamic processes in the disk windings of a power transformer is proposed, which, unlike the existing ones, takes into account the width of the horizontal channel less than 3 mm, which allows to predict the heat distribution in the winding and determine possible locations overheating of coils and premature destruction of insulating materials.

CFD simulation of airflow in a new receiver concept for solar tower

51%

Cheilytko A. , Nohutcu O. , Schwarzbözl P. , Broeske R. T.

tom Vol. 7, nr 3

83--98

Open cavity solar receivers play an important role in concentrated solar power (CSP) systems and hold great promise, particularly in scenarios where their ability to absorb high fluxes at very high temperatures yields beneficial results. This intense concentration of sunlight can be used to produce electricity through various means, such as generating steam to drive a turbine. The efficiency of the open volumetric receiver concept relies heavily on the air return ratio (ARR) which refers to the proportion of air recirculated and returned to the receiver. A high ARR contributes to high receiver efficiencies, as with rising ARR, the reused part of the enthalpy of warm air increases. This paper deals with the design and simulation of a new receiver concept with a conical cavity and square cross-section. The objective is to identify the most effective design arrangement for the square-cone structure, considering different depths, that maximizes both the air return ratio (ARR) and thermal efficiency. The findings demonstrate that increasing the depth of the mentioned receiver leads to a rise in the ARR, up to a certain threshold which can reach values up to 94.53%, beyond which there is a subsequent decline in efficiency. Furthermore, this study examined how varying the amount of air passing through a specific section of the receiver across a defined area, along with the temperature changes in these sections, affected its operational efficiency.