Theoretical research of heat exchange between air flow and shaft lining subject to convective heat transfer

Abstract

The heat and mass transfer in a mine shaft under construction is researched theoretically under temperature conditions in the shaft lining lower than the temperature of air flow fed in the shaft via a ventilation duct. The research was aimed to ensure stable airing of mine shafts in the period of construction before cutting a shaft-to-shaft connection with artificial freezing of surrounding rock mass. The multi-parametric numerical modeling of nonstationary aeroand thermo-dynamic parameters in a mine shafts was performed using 3D convective heat transfer model in ANSYS. It is found that convective heat can exert considerable influence on the heat and mass exchange in the air space of the shaft when the shaft lining temperature is lower than the temperature of air flow from the ventilation duct at the shaft bottom. Inside the shaft, the back convective flows appear and air circulates in convective cells, which increases air flow rate in the shaft. As a consequence, the heat transfer factor at the shaft lining-air interface is much higher than the calculated factor without regard to the convective heat. The influence of the temperature difference at the air and shaft lining interface and the shaft lining roughness on the average values of the heat transfer factor and heat flow at the shaft lining and air interface is investigated. The empirical formulas are proposed for calculating the heat transfer factor and specific heat flow at the shaft lining and air interface depending on the temperature difference, shaft diameter and roughness of walls of underground openings.