International Journal of Heat and Mass Transfer, Vol.131, 594-603, 2019
Thermal characteristics of cement microparticle-stabilized aqueous foam for sealing high-temperature mining fractures
The fractures formed at high temperatures by the heat damage of coal and rock are the main causes for the evolution and spread of coal fires. Cement microparticle-stabilized aqueous foam is a new type of material for preventing and controlling coal and rock fractures at high temperatures. The thermal characteristics of the foam fluid are the most important technical parameters. The morphological changes of the foam fluid under different hot surface temperatures were characterized, and the mechanism of the effect of heating on the stability of the liquid film was studied based on the kinetic energy of the surfactant molecules and particle hydration. Using a homemade testing system, the thermal insulation properties of foam fluid with different bracket heights (2 cm, 7 cm, 12 cm, 17 cm, and 22 cm) and injection thicknesses (20 mm, 40 mm, 60 mm, and 80 mm) were tested. It was concluded that the cold surface temperature of all the foam fluids from 20 mm to 80 mm increased with increasing temperature; however, the rate of temperature increase within 0-90 s was greater than that within 90-300 s. The thermal insulation temperature was distributed on a Gauss cum surface, and the relationship of the thermal insulation temperature with the hot surface temperature and thickness was fitted. On the foundation of the traditional steady-state method, a new effective thermal conductivity measurement apparatus with a half-globular shape was developed, and its principle of operation and experimental setup were described. The effective thermal conductivity fluctuated slowly between 0.1222 and 0.2974 W/m.K within the temperature range of 323-373 K. The empirical correlation to calculate the thermal conductivity of the cement microparticle-stabilized aqueous foam at different temperatures was obtained. (C) 2018 Elsevier Ltd. All rights reserved.