Evaluating cooling placement strategies of mobile cooling units in deep-level mines

Abstract

Deep-level gold mines in South Africa face unique challenges, such as high underground air temperatures, due to their extreme depths. Tertiary cooling systems are essential for regulating workplace temperatures, but space and cost constraints require that profitability and worker safety be optimised. This thesis addresses the critical need to enhance the efficiency of tertiary cooling systems by determining the ideal placement of mobile cooling units in mining levels. The location of cooling units is often subjectively chosen by mine personnel due to the complex nature of mine ventilation networks. Limited information in the literature makes it difficult to consider additional influencing factors, such as air being reused, varying depths underground, and air travel distances. To bridge this gap, a simulation-based method was developed to compare three cooling unit placement strategies with one another. Simulation modelling, a powerful tool for solving complex problems, was used to predict changes in temperature under varied cooling scenarios.

The proposed method was tested across four study levels in two different mines, each characterised by distinct influencing factors that affect workplace temperatures. The results demonstrated that a spot cooling strategy performed well in areas with high heat loads and low air quantities. This approach suits widely spaced workplaces. Conversely, centralised cooling proved effective for higher air quantity levels and for workplaces located within 1.5 km from the common air intake point. However, it struggled with longer air travel distances. The bulk cooling strategy was comparable to the centralised cooling strategy, but it was better suited to levels supplied by multiple air intake points.

In conclusion, this thesis contributes significant insights into the intricate relationship between cooling unit placement and workplace temperatures in deep-level gold mines. It introduces a comprehensive simulation-based method that empowers mine ventilation officers and system engineers to derive the optimal placement of mobile cooling units. Applied to case studies, this method provides an in-depth understanding of each strategy’s strengths and limitations, offering a crucial foundation for informed decision-making.