Hot dry rock is an abundant, stable and low-carbon geothermal resource, which has a promising prospect for power generation in China. In this paper, a hot dry rock power generation system model based on conventional organic Rankine cycle was established. The performance of the system was evaluated by thermodynamic analysis, as well as energy and exergy analyses. Four types of organic working fluids were selected to investigate their effects on system energy efficiency. R114 had much higher energy efficiency (17.50%~ 19.00%) than other three organic working fluids (R245fa, R245ca and R601) when water flow rate ranged from 80 t/h to 260 t/h. When R245fa was used as working fluid and power output was set at 4 MW, energy and exergy efficiency of the system were 15.27% and 50.42%, respectively. According to the energy flow analysis, the major energy losses (15.67 MW) in the system were attributed to the discharge temperature of turbine exhaust. However, exergy flow analysis indicated that the energy loss from turbine exhausts was not as serious as expected, since the work potential of that energy was limited. The exergy destruction of each component in the system was calculated, and the results showed that heat exchanger and the vapor separator were the weakness components in the system, and they respectively contributed to 44.8% and 29.8% of the total exergy destruction. The results obtained in this study provide possible strategies to improve the overall performance of the hot dry rock power generation system based on conventional organic Rankine cycle.

Background The optimal treatment strategy for Pauwels type III femoral neck fractures remains controversial. A new internal fixation femoral neck system (FNS) for the treatment of femoral neck fractures was developed, and we compared the mechanical efficiency of the internal fixation FNS with that of two cannulated screw configurations for the treatment of Pauwels type III femoral neck fractures. Method: In this study, we constructed models of Pauwels type III femoral neck fractures with angles of 50°, 60°, and 70°. Moreover, a fixation model with the FNS and two fixation models with cannulated screws were developed. Under two axial loads, 1400 N and 2100 N, the von Mises stress distributions, maximum von Mises stress, and displacements of the femur and internal fixation components were measured for each fracture group. Result The maximum von Mises stress of internal fixation in the three models was mostly located near the fracture line, and the femoral head region closest to the femoral calcar experienced the maximum amount of stress. As the Pauwels angle and axial loads increased, the stress and displacement of the proximal femoral head and internal fixation component increased in each group. Compared with cannulated screw configurations, the internal fixation FNS showed lower values of peak stress at the femoral head and smaller displacements of the femur and internal implant in the treatment of Pauwels type III femoral neck fractures with Pauwels angles of 50°, 60°, and 70°. Conclusion The newly developed internal fixation FNS provided improved biomechanical stability for the treatment of Pauwels type III femoral neck fractures, which indicated that the internal fixation FNS may be a new option for the treatment of vertical femoral neck fractures.

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