Izvestiâ Vysših Učebnyh Zavedenij i Ènergetičeskih ob Edinennij SNG. Ènergetika (Jun 2019)
Discrete Optimization of Software-Controlled Modes of Heat Treatment of Concrete Products in Heat-Technological Facilities
Abstract
In the article the technique of an assessment of modes of operation of the heat engineering equipment used for heat treatment of concrete products in the conditions of programcontrolled heat supply according to the pattern of “heating – isothermal influence – cooling” has been developed. The method is based on the numerical solution of a non-stationary heat equation supplemented by equations describing the hydration process of a concrete product; also, it includes a system of initial and boundary conditions for its spatial structure. The method makes it possible to create tabulated functions of temperature and the degree of hydration of the time of heat treatment in any point of a 3D-product. The mathematical tools for calculating the functional dependencies of concrete hydration equipment with software-heated environment are presented. Numerical calculations of the concrete hydration process in the formwork are performed with respect to the symmetrical object. Based on the calculation of the temperature gradient across the minimal cross section of the product, a numerical analysis of the functions modeling heat supply mode depending on the processing time of a concrete product has been fulfilled. It is demonstrated that the maximum speed of the hydration process in a concrete product hardening is achieved at the maximum of time lag of isothermal cure. Additionally, with an increase in the duration of the product heating, the value of the maximum hydration rate decreases. It is concluded that the method of assessing the mode of heat treatment of concrete products being developed makes it possible to determine parameters for the calculation of the minimal useful heat required for the heat treatment of concrete products with spatially distributed parameters. The proposed method is applicable to calculate the temperature fields and the extent of hydration in the products of any geometric shape and volume in a software-controlled heating environment of industrial facilities for the accelerated hydration of concrete, and also affords the possibility of preliminary calibration prior to the assignment of relevant heat supply modes to the products being processed.
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