Characteristic studies of heat sources and performance analysis of free-cooling assisted air conditioning and ventilation systems for working faces of mineral mines

Abstract

High temperature heat hazard at mineral mine becomes more and more serious as the increase of mining depth. Heat sources at working faces of mineral mines are complex and are of different characteristics, presenting new challenges for air conditioning systems. In this paper, heat sources at four types of working faces are summarized and their characteristics are investigated. Based on this, simplified equations, which are linear with length of working faces, are proposed to calculate heat dissipation rates. So that the main heat sources of different working faces can be found, and cooling load of air conditioning systems can be calculated. Then, considering main heat sources of coal mines, a typical working face is designed to investigate performances of different ventilation systems and air conditioning systems. Simulation results show that segmented ventilation systems (SC) and heat shield assisted centralized ventilation systems (CCHS) can realize much better temperature distributions at working faces. However, cooling load can be greatly reduced for CCHS, when untreated air is supplied to the coal seam side. Based on this, free cooling assisted air conditioning systems are designed, and annual average energy efficiency ratio (EERann) of the systems are investigated and compared between direct evaporate cooling and indirect evaporate cooling (IEC). For SC, as compared with scenarios without free-cooling, IEC can increase EERann by 15%–23% and 22%–32% under Benxi and Datong ambient conditions, respectively. Besides, to ensure high EERann, CCHS is preferred and it is essential to increase thermal insulation of air ducts.