The analysis and simulation of heat flow in longwall coal faces

Author: D., Ch. Panigrahi

The paper presents the development of two simulation models for predicting the climatic condition in mechanised longwall faces.

One of these models is based on a linear heat flow concept which considers the longwall face as a semi-infinite solid consisting of three sides, viz. roof, face and floor strata, and the goaf is not considered as a continuous strata for heat emission.

Heat from the goaf is carried by goafleakage air andjoins the face airflow at a few discrete points along its length. In order to consider the time of exposure of strata for heat flow purposes, the time-based development stage (referred to as the age) is calculated by forming rectangular elements (consistent with the finite element approach) in the roof, face and f100r strata.

The width of each element is equal to the web depth of the shearer and the length is equal to the incrementallength considered in the simulation. The heat flow is calculated for each element separately, summed up for the increment and numerically integrated over the total length of the longwall face.

Another simulation model based on a radial transient heat flow algorithm considering the longwall face in the form of a cylindrical tunnel has been developed and in this case a representative age has been calculated from the ages of all the elements of an increment. In both models the contribution by machinery and other sources to heat and moisture levels, viz. the shearer, the armoured flexible conveyor (AFC), coal being conveyed, goaf leakage air etc. have been duly considered.

Extensive field investigations have been camed out in five longwall paneis of five coal mines to validate these simulation models.

A satisfactory correlation has been obtained for both the models, therefore either of these models may be used to predict the climatic conditions in longwall faces.