Abstract
Temperature distribution in concrete is significant to the concrete structure’s macro properties and different factors affect the heat transfer in concrete, and therefore influence the temperature distribution. This work established a three-dimensional transient heat transfer model coupled with various environmental factors, using the finite element method for calculating the results and real-measured data for testing accuracy. In addition, a sensitivity evaluation of various factors was conducted. Due to various environmental factors, the results revealed that the prediction of temperature distribution in concrete by the three-dimensional model had great accuracy with an error of less than 4%. A particular hysteresis effect of temperature response in the concrete existed. Considering heat transfer in different spatial directions, the model can predict the temperature change of each spatial point instead of the spatial surface in different depths, proving the shortcomings of a one-dimensional heat transfer model. A greater solar radiation intensity caused a more significant temperature difference on the concrete surface: the surface temperature difference in July was twice as significant as that in December. Wind speed had a cooling effect on the concrete surface, and stronger wind speed accompanied with a stronger cooling effect made the surface temperature closer to the ambient temperature. Material properties had different effects on the temperature distribution of the surface part and internal part: the specific heat capacity determined the speed of the outer layer temperature change while the thermal conductivity determined the speed of the inner layer temperature change.
Highlights
Most concrete structures are located in the atmosphere, suffering from environmental conditions such as sunshine, wind, and changing temperature
Due to the concrete surface being directly exposed to atmospheric factors, it has a quicker response to the external temperature than internal concrete, resulting in inhomogeneous internal temperature distribution, that is, temperature field
When the concrete is exposed to the natural environment, the expansion of the thermal boundary layer of the concrete is free of constraint, and the interaction between the fluid and the surface is driven by natural wind, which can be simplified as forced convection
Summary
Most concrete structures are located in the atmosphere, suffering from environmental conditions such as sunshine, wind, and changing temperature. With an in-depth understanding of the actual natural conditions, radiation and atmospheric convection were investigated to affect the inner temperature distribution, and were incorporated into prediction models experimentally and theoretically. Cho et al [24] established an internal temperature and relative humidity (RH) prediction model to describe the evolution of internal temperature and relative humidity in concrete under the coupled actions of radiation, convection, and ambient temperature, based on the basic principle of one-dimensional unsteady heat conduction. This work focuses on the change of temperature distribution in concrete under a natural environment following Fourier’s law, thermodynamic principle, and numerical solution theories. Basic principles were introduced as follows [28]: Convective and radiant heat transfer are two primary forms occurring on the surface of the concrete. The internal and external energy began to flow continuously, with the internal temperature distribution changing
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