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Deng H.,North China Electrical Power University | Bai Y.,North China Electrical Power University | Li X.,China Power Complete Equipment Co. | Zhang D.,Beijing GDZS Control Technology Co
Huagong Xuebao/CIESC Journal | Year: 2016

Considering the interfacial shear force, a mathematical model to the condensation of turbulent vapor flowing downward in an inclined flat tube is proposed and implemented in computational fluid dynamics (CFD). The predicted results from the CFD model are compared with the experimental results from the literature for the vapor condensation in a prototype tube (2600 mm length, 3 mm width and 50 mm altitude in 60° inclination to vertical). It is found that the condensate rate and mean condensation heat transfer coefficient (HTC) from CFD simulation agree very well with the experimental quantities. Using CFD model to calculate the interfacial shear stress by varying vapour velocity, the results demonstrate that the value of shear force depends on the vapor velocity at the tube inlet, and shear force decreases continuously with the vapor flow and condensation. Simulating the interfacial shear effect on the condensation, it shows that the interfacial shear increases the local condensation HTC, and meanwhile, reduces the local condensate rate. The simulation results also shows that the interfacial shear weakens the gravitational effect on the film accumulation and obviously decreases film thickness from 0 to 0.8 m in the tube axial length. However, from 1.0 m to the tube outlet, the gravitational force dominates over the shear force, and thus the shear effects can be completely neglected. It is also found that the condensate film is speeded up particularly from 0 to 0.2 m in axial length thanking for the interfacial shear. © All Right Reserved. Source

Yuan G.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Wang T.,China Power Complete Equipment Co. | Du J.,North China Electrical Power University
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2015

According to the characteristics of energy-saving assessment in thermal power plant, a comprehensive gray relation projection evaluation method based on ideal point was proposed by introducing the TOPSIS, gray correlation theory and vector projection method to the unit performance evaluation. Meanwhile, the weight of evaluation index was determined by combining the Delphi with sequence synthesis technique using combination weighting method, so as to improve the scientific level and objectivity of energy-saving assessment for thermal power plant. Above methods were applied to the comprehensive evaluation of five 600 MW units, while a sensitivity analysis of the subjective weights was carried out. Results show that the indicator of both the economy and reliability is still dominant in the unit comprehensive evaluation; the model of gray relation projection evaluation based on TOPSIS is able to quantitatively evaluate the energy-saving status with high evaluation robustness, which therefore may serve as a reference for energy saving of relevant power plants. ©, 2015, Shanghai Power Equipment Research Institute. All right reserved. Source

Yan Z.,China Power Complete Equipment Co.
Gaoya Dianqi/High Voltage Apparatus | Year: 2015

The larger the capacity of a generating unit is, the greater the electromagnetic force on the enclosure type isolated-phase bus becomes in short circuit fault condition. In the related national and industrial standards with enclosure type isolated-phase bus, the requirements for axial welding are unclear. In this paper, a force analysis of the enclosure type isolated-phase bus in short circuit condition is conducted for a 1250 MWe nuclear power project, and some suggestions are provide for axial welding requirements of large capacity enclosure type isolated-phase bus. ©, 2015, Xi'an High Voltage Apparatus Research Institute. All right reserved. Source

Li Y.,China Power Complete Equipment Co. | Ren X.-D.,Hong Kong University of Science and Technology
Applied Thermal Engineering | Year: 2016

Energy and environment issue set utilizing low-grade heat noticed. Organic Rankine Cycle (ORC) has been demonstrated to be a promising technology to recover waste heat. As a critical component of ORC system, the turbine selection has an enormous influence on the system performance. This paper carries out a study on the thermodynamic analysis of ORC system and the aerodynamic design of an organic radial turbine. The system performance is evaluated with various working fluids. The aerodynamic design of the organic radial-inflow turbine is focused due to the high molecule weight and the low sound speed of the organic working fluid. An aerodynamic and profile design system is developed. A radial-inflow turbine with R123 as the working fluid is designed and the numerical analysis is conducted. The simulation results indicate that the shock wave caused by the high expansion ratio in the nozzle is well controlled. Compared with the one-dimensional design results, the performance of the radial-inflow turbine in this paper reaches the design requirements. © 2015 Elsevier Ltd. All rights reserved. Source

Bai Y.,North China Electrical Power University | Deng H.,North China Electrical Power University | Li X.,China Power Complete Equipment Co. | Zhang D.,Beijing GDZS Control Technology Co
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2016

The single-row flat wave finned tube is widely applied as the unit tube by the direct air cooled condenser in power plants. Caused by the complicated body geometry in fin side, the vapour condensation involving phase transition, and the heat transfer from vapour zone to air zone conjugating on several interfaces, using computational fluid dynamics (CFD) method to simulate the heat transfer in both the vapour channel and the cooling air channel simultaneously, many challenges are encountered. A mathematical model to simulate the condensation of water vapour was developed counting the interfacial shear stress, the heat balance conditions on the interfacial boundaries of the conjugate heat were presented as well as the method to calculate the conjugate heat. The numerical simulation for the full-size finned tube was carefully separated to 282 CFD modules which share same boundaries each other. Based on the 282 CFD modules, the asynchronous strategy to calculate the conjugate heat of the finned tube in overall scale was successfully carried out. The results from the CFD simulations agree very well with the experimental results, which validates the proposed condensation model, also show the great potential of the asynchronous CFD approach as an effective tool for the full-size finned tube to predict the heat transfer in both sides. Based on the CFD results, the characteristics of flow field was also investigated in terms of both the cooling air and the vapour. © 2016 Chin. Soc. for Elec. Eng. Source

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