The Effects of Thermal History on Mine Climate Simulation Results
George Danko, University of Nevada, Reno; Chao Lu, University of Nevada, Reno
High temperature at the working face may jeopardize safety in deep and hot underground mines. Careful design is needed for finding optimum solution for safety, health, and cost. It is necessary to predict during design the dynamic changes in temperature with heat emitted into the mine ventilation-thermal-humidity (V-T-H) system from various sources such as auto-compression, wall strata, mining equipment and other sources. The complexities of dealing with the heat flow problems in the V-T-H systems in deep mines are well recognized and mine climate simulation programs gradually incorporate the dynamic transport of heat and mass in the strata wall around the mine airways. Currently available mine ventilation and climate models are either furnished with a step-change-type thermal solver (such as in Climsim), or with more advanced models to account for the “thermal history effect” (also known as thermal flywheel effect), such as in Ventsim and MULTIFLUX. The goal is to understand the question of how large modelling error occurs if the model does not have the thermal history component, therefore, lacks the ability to deal with the “thermal history effect.” Two models are compared: one with and one without the thermal history component to process past and current temperature flow data. A long single drift is used for the long-term climate simulation tests. Several scenarios are tested on various model conditions such as different air flow rate, rock thermal properties, virgin rock temperature and heat production from mining operations. The examples illustrate the magnitude and the time-lag phase of the variation of the modelling errors with space, time and model conditions. Conclusions are drawn to advise the ventilation engineer as to when and where a simple, step-change thermal history model can be applied for the acceptable design accuracy.