Applying the CO2-Based Mixture to Realize Efficient and Low-Cost Cooling for Deep Underground

Abstract The problem of heat hazard restricts the safe and efficient mining of deep mineral resources. A heat pump for simultaneous cooling and heating can control the heat hazard of deep mine and satisfy the heat load for mining community. However, the traditionally used working fluid of a heat pump, namely R22, possesses the disadvantages of being environmentally unfriendly and expansive operating cost. A CO2-based mixture is a promising substitute for R22 because of its excellent physical properties and great thermal match performance. This study carries out the thermo-economic analysis of a transcritical heat pump with the CO2-based mixture, and the feasibility of replacing R22 with the CO2-based mixture is investigated. The results show that the introduction of the CO2-based mixture can significantly cut down the irreversible loss in condensation and evaporation processes. R161 is the optimal additive for the CO2-based mixture, and the optimal COPc of CO2/R161 is 2.48, which is 12.2% higher than CO2 and 8.3% higher than R22. Although the initial capital cost of a heat pump with CO2/R161 is 24.2% higher than R22, the annual running cost is 6.39% less than R22, and substituting CO2/R161 for R22 can save operating cost by 1.62 × 106 CNY/year.