| 内容提要: |
This research presents a novel reverse Carnot cycle-organic Rankine cycle (RCC-ORC) dual-function system (DFS) for electricity and heat output using a two-screw machine which consists of heat pump (HP) mode and power generation (PG) mode. Compared with single PG and HP system, the proposed system can recover low-grade waste heat to generate electricity or high-grade thermal energy in accordance with consumer demand. A mathematical model has been established to analyze the variation of the energy, exergy, economic and environmental performance with different temperature. Simulation results show that the DFS has good feasibility and stability in two modes. In addition, there is a contradiction between the exergy performance and economic performance. When the DFS has shorter payback period (PBP) of 1.39 year, the irreversible destruction is high at 225.58 kW. Therefore, the optimized DFS should be determined according to the exergy performance and economic performance. TOPSIS method is chosen as the decision method to select the final optimal value of the system. The optimization results show that if the optimized payback period project is chosen, PBP is 30% shorter than its largest possible value at the condensing temperature of 120℃; whereas, if exergy destruction based optimized design is chosen, exergy destruction is 6.5% more than the smallest possible value. At the optimal condition, the heat output and electricity are 945.7 kW 81.9 kW, respectively. Payback period and exergy destruction are 4.34 year and 201.21 kW, respectively. |