Based on organic Rankine cycle(ORC), the two-stage evaporation strategy is adopted to replace the single-stage evaporation to improve the system performance. In order to evaluate the temperature matching of the two-st...Based on organic Rankine cycle(ORC), the two-stage evaporation strategy is adopted to replace the single-stage evaporation to improve the system performance. In order to evaluate the temperature matching of the two-stage evaporation, a theoretical optimization model was established to optimize the two stage organic Rankine cycle(TSORC) based on the entransy theory and thermodynamics, with the ratio of the entransy dissipation rate of the TSORC to that of the ORC as the objective function. This paper aims to illuminate the improving degree of the system performance of the TSORC. The results show that the TSORC enhances the average evaporating temperature, thereby reducing the entransy dissipation rate in the evaporator and the total entransy dissipation rate. The maximal net power output is proportional to the entransy loss rate and inversely proportional to the entransy dissipation rate. However, compared with the ORC, the TSORC can output more power but requires a higher total thermal conductance. Moreover, there exists an optimal intermediate geothermal water temperature(IGWT) to maximize the net power output of the TSORC. The TSORC can be considered in engineering applications.展开更多
The design, construction and test of an Organic Rankine Cycle(ORC) with R123 as the working fluid were performed. A scroll expander was integrated in the system.The conductive oil with its temperature of 150 °C w...The design, construction and test of an Organic Rankine Cycle(ORC) with R123 as the working fluid were performed. A scroll expander was integrated in the system.The conductive oil with its temperature of 150 °C was used to simulate the low-grade heat source. An AC dynamometer unit measured the expander shaft torque, rotating speed and shaft power. The experiments were conducted in two operating modes: the constant mass flow rate and the constant shaft torque. Under the constant mass flow rate operating mode, the stepped increase of the shaft torque increased the expansion ratios of the expander and decreased the vapor superheats at the expander inlet. Thus,the shaft power and thermal efficiency were increased.Alternatively, the constant shaft torque operating mode involved two different regions, interfaced at the pumping frequency of 9 Hz. By the increase of the mass flow rates,the vapor superheats at the expander inlet was decreased and the shaft power was increased, but the ORC thermal efficiencies were slightly decreased. Both operating modes yielded the saturation shaft powers that were the maximum values one could use. It was found that the measured shaft powers and ORC thermal efficiencies were lower than the enthalpy determined values based on the fluid pressures and temperatures at the expander inlet and outlet. The maximum measured shaft power and thermal efficiency were 2.63 kW and 5.31 %, compared with the enthalpy determined values of 3.87 kW and 9.46 %, respectively.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51406130)
文摘Based on organic Rankine cycle(ORC), the two-stage evaporation strategy is adopted to replace the single-stage evaporation to improve the system performance. In order to evaluate the temperature matching of the two-stage evaporation, a theoretical optimization model was established to optimize the two stage organic Rankine cycle(TSORC) based on the entransy theory and thermodynamics, with the ratio of the entransy dissipation rate of the TSORC to that of the ORC as the objective function. This paper aims to illuminate the improving degree of the system performance of the TSORC. The results show that the TSORC enhances the average evaporating temperature, thereby reducing the entransy dissipation rate in the evaporator and the total entransy dissipation rate. The maximal net power output is proportional to the entransy loss rate and inversely proportional to the entransy dissipation rate. However, compared with the ORC, the TSORC can output more power but requires a higher total thermal conductance. Moreover, there exists an optimal intermediate geothermal water temperature(IGWT) to maximize the net power output of the TSORC. The TSORC can be considered in engineering applications.
基金supported by the National Basic Research Program of China(2011CB710703)the National Natural Science Foundation of China(51306048,51210011)
文摘The design, construction and test of an Organic Rankine Cycle(ORC) with R123 as the working fluid were performed. A scroll expander was integrated in the system.The conductive oil with its temperature of 150 °C was used to simulate the low-grade heat source. An AC dynamometer unit measured the expander shaft torque, rotating speed and shaft power. The experiments were conducted in two operating modes: the constant mass flow rate and the constant shaft torque. Under the constant mass flow rate operating mode, the stepped increase of the shaft torque increased the expansion ratios of the expander and decreased the vapor superheats at the expander inlet. Thus,the shaft power and thermal efficiency were increased.Alternatively, the constant shaft torque operating mode involved two different regions, interfaced at the pumping frequency of 9 Hz. By the increase of the mass flow rates,the vapor superheats at the expander inlet was decreased and the shaft power was increased, but the ORC thermal efficiencies were slightly decreased. Both operating modes yielded the saturation shaft powers that were the maximum values one could use. It was found that the measured shaft powers and ORC thermal efficiencies were lower than the enthalpy determined values based on the fluid pressures and temperatures at the expander inlet and outlet. The maximum measured shaft power and thermal efficiency were 2.63 kW and 5.31 %, compared with the enthalpy determined values of 3.87 kW and 9.46 %, respectively.
