Dynamic Evolution Characteristics of the Wall Temperature of the Drill Bit and Core Tube in Coal Seam Coring

Summary Reducing the amount of gas lost during the coal sample collection process is one of the key factors for improving the accuracy determination of coal seam gas content (CSGC). To realize the accurate calculation of fixed-point coring and gas loss, the thermodynamic model is established. The numerical model is verified by the real-time monitoring results of the pipe wall temperature, and then the temperature evolution law of the coring process and the coring tubes at different depths is revealed. The heat flux of the same process is the same, regardless of the coring depth. In the cutting process, the overall temperature tends to be uniform while the heat is transmitted upward. For Node A, the node temperature after 1 second of cutting by the cutting teeth increases with the cutting depth (drilling pressure), and the node temperature increases with the rotational speed of the coring drill bit. The temperature change at Node A is most sensitive to the increase in rotational speed. Whether the ambient temperature changes or not, whether the film heat dissipation coefficient (FHDC) is large or not, the temperature measurement point has been decreasing, and the cooling rate is getting smaller and smaller.