Justification of the parameters and operation modes of a thermal accumulator with a solid accumulative material of a porous structure for heliothermal installations
DOI:
https://doi.org/10.31734/agroengineering2022.26.077Keywords:
heat accumulator, heat and mass exchange, heliothermal installationAbstract
A new type of battery with a solid heat-accumulating material of a porous structure has been developed for a heliothermal installation, which is based on the use of an environmentally friendly and renewable source of thermal energy - solar radiation and accumulated heat.
The structural and technological scheme of the plug-in heat accumulator using pebbles was substantiated and its modes of operation were analyzed. In order to evaluate the battery efficiency, the following factors are determined, in particular, the spectral composition of the absorbed radiation that determines the rate of pebbles heating, organization of the radiation field due to the control of the the coolant flow, properties of the material under study and the leakage of the medium, changes in the conditions of heat exchange, geometric parameters of the battery.
A mathematical model was obtained. It can be used to calculate the amount of absorption of the temperature gradient in the conditions of a stationary porous layer of pebbles and to regulate the depth of heat flow penetration for a specific layer of the battery in which phase transformations take place.
A method of engineering calculation of thermal fields for a stationary porous layer of pebbles and recommendations for their successful use in a heliothermal installation to ensure its operation at night and in partly cloudy conditions are proposed. The choice of such heat-accumulating elements was based on the study of the heat flow in the porous layer and the energy of convective heat exchange. It was established that a layer of pebbles with a porous structure is the most promising in terms of its use as a solar radiation accumulator in the temperature regime of 30...50 ºС. By using the layer, the energy supplied to the heat accumulator was 615.4 kJ, and the heating of the heat-accumulating material with the weight of 50 kg per 1 ºС made it possible to accumulate 42.25 kJ/ºС of heat.
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