The unsteady heat transfer test of the surrounding rock

The heat transfer between airway and airflow is an unsteady problem. Three experimental schemes (1, Variable wind temperature, the temperature of air flow are 15°C, 20°C, 25°C, 30°C; 2, Variable speed, wind speed are 1m/s, 2m/s, 3m/s; 3, Periodic wind temperature, 15°C~25°C and 20°C~30°C) are used to simulate the actual heat transfer process between airway and airflow. Test results show that it exists obvious unstable heat transfer characteristics; the temperature of airway is stable in the last. And the temperature increased with the decreasing difference in temperature between air flow and surrounding rock; and the time required to reach a steady was reduced; with the increase of airflow speed, the stable temperature of the soil was lower and the time required to reach a steady was reduced; when airflow temperature periodic changes, the heat transfer in the soil has obvious "lag" effect. The entire heat transfer process can be divided into severe heat section, excessive heat segment and stable heat section.