The Enhanced Geothermal System(EGS) is a recognized geothermal exploitation system for hot dry rock(HDR), which is a rich resource in China. In this study, a numerical simulation method is used to study the effects of...The Enhanced Geothermal System(EGS) is a recognized geothermal exploitation system for hot dry rock(HDR), which is a rich resource in China. In this study, a numerical simulation method is used to study the effects of geothermal fluid dryness and non-condensable gas content on the specific enthalpy of geothermal fluid. Combined with the organic Rankine cycle(ORC), a numerical model is established to ascertain the difference in power generation caused by geothermal fluid dryness and non-condensable gas content. The results show that the specific enthalpy of geothermal fluid increases with the increase of geothermal fluid temperature and geothermal fluid dryness. If the dryness of geothermal fluid is ignored, the estimation error will be large for geothermal fluid enthalpy. Ignoring non condensable gas will increase the estimation of geothermal fluid enthalpy, so the existence of the non-condensable gas tends to reduce the installed capacity of a geothermal power plant. Additionally, both mass flow of the working medium and net power output of the ORC power generation system are increased with increasing dryness of geothermal fluid, however there is some impact of geothermal fluid dryness on thermal efficiency.展开更多
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
基金support provided by the National Key Research and Development Program of China(Grant No.2018YFB1501805)the National Natural Science Foundation of China(Grant No.52176183)。
文摘The Enhanced Geothermal System(EGS) is a recognized geothermal exploitation system for hot dry rock(HDR), which is a rich resource in China. In this study, a numerical simulation method is used to study the effects of geothermal fluid dryness and non-condensable gas content on the specific enthalpy of geothermal fluid. Combined with the organic Rankine cycle(ORC), a numerical model is established to ascertain the difference in power generation caused by geothermal fluid dryness and non-condensable gas content. The results show that the specific enthalpy of geothermal fluid increases with the increase of geothermal fluid temperature and geothermal fluid dryness. If the dryness of geothermal fluid is ignored, the estimation error will be large for geothermal fluid enthalpy. Ignoring non condensable gas will increase the estimation of geothermal fluid enthalpy, so the existence of the non-condensable gas tends to reduce the installed capacity of a geothermal power plant. Additionally, both mass flow of the working medium and net power output of the ORC power generation system are increased with increasing dryness of geothermal fluid, however there is some impact of geothermal fluid dryness on thermal efficiency.
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.
