Heat Transfer Characteristics and Temperature Regulation of Energy-Saving Working Fluids in Water-Ring Vacuum Pumps for Gas Extraction

Water-ring vacuum pumps for coal mine gas extraction often operate at high temperatures and low efficiency, which limits extraction capacity and system stability. This study investigated how xanthan gum concentration, working-fluid temperature, and entrained coal dust affect the rheology, flow resistance, and heat transfer performance of a xanthan-gum-based energy-saving working fluid and evaluated a corresponding cooling and efficiency-improvement system. Rheological tests and counterflow plate heat-exchanger experiments were conducted under different xanthan gum concentrations, temperatures, and coal-dust contents, followed by field verification at Licun Coal Mine. Increasing xanthan gum concentration weakened heat transfer and increased flow resistance: the maximum heat transfer reduction relative to water increased from 9.5% to 50.5%, while the maximum friction-coefficient increase rose from 6.8% to 24.0%. Increasing temperature raised the Nusselt number by up to 22.6% and reduced the friction coefficient. Coal dust exhibited a concentration-dependent dual effect; at representative flow velocities, 1,000 ppm coal dust increased the Nusselt number by 5.3%, whereas 10,000 ppm coal dust reduced it by 18.6%. In field operation, the optimized system reduced the inlet working-liquid temperature from approximately 35°C to 15°C and the pump operating temperature from 64°C to 42°C. The suction flow rate increased from 119 to 127 m 3 / min , corresponding to an increase of approximately 6.7%, while the operating power remained approximately 800 kW. These results clarify the coupled rheology–flow–heat transfer mechanism and provide an engineering basis for the stable and energy-efficient operation of water-ring vacuum pumps under coal-dust-containing conditions.