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Dang W.,Xian Aeronautical University | Shen S.,Thermal Power Research Institute
World Information on Earthquake Engineering

It is well established that the use of lateral confinement can significantly enhance the strength and ductility of high-strength concrete (HSC), and reasonable selection of constitutive model of HSC has largely effect on nonlinear analysis of structure elements. This paper presents a study on the behavior and modeling of the stress-strain curves of confined HSC under triaxial compression by collecting 281 test results. The peak stress and corresponding peak strain model are established. To evaluate the accuracy of proposed model, the calculated results are compared with results from other existing model, such as Attard and Setunge model, Candappa model, Lu and Hsu model and Jiang and Teng model. Based on the stress-strain equation originally proposed by Popovics model, a constitutive model for both the actively confined normal and high strength concrete is also established. It is eventually found that the peak stress and peak strain model shows more accuracy than other existing models for actively confined HSC. The stress-strain curves predicted by the analysis-oriented constitutive model are in close agreement with the experimental curves, which provided theoretical basis for the nonlinear analysis of structure elements. © 2016, Science Press. All right reserved. Source

Sun Z.,Xian Jiaotong University | Gao L.,Thermal Power Research Institute | Wang J.,Xian Jiaotong University | Dai Y.,Xian Jiaotong University

The industrial waste heat parameters, like flow rate and temperature, usually fluctuate in a certain range due to the variation of upstream industrial process. However, the heat recovery systems are usually designed not under the fluctuation range but under a specific point, therefore, the most reasonable design condition of the waste heat should be estimated based on the fluctuation ranges. A single pressure waste heat recovery system was studied in this paper. Static models were developed for system design and dynamic models were established to simulate the system transient performance when the temperature or flow rate of exhaust gas fluctuates. Systems designed at different exhaust gas parameters were operated under the same fluctuation condition to find out which one could generate the maximum net power. The fluctuations of temperature and flow rate of exhaust gas were studied separately. The results show that systems designed at the upper boundary of fluctuation range of exhaust gas could generate more power. In the case of temperature fluctuation of exhaust gas, the optimal turbine inlet pressure obtained by dynamic analysis is 7.9% lower than that of static analysis. It is 4.6% higher than that of static analysis in the case of flow rate fluctuation. © 2012 Elsevier Ltd. Source

Wang Y.-G.,Xian Jiaotong University | Zhao Q.-X.,Xian Jiaotong University | Zhang Z.-X.,Thermal Power Research Institute | Zhang Z.-C.,Xian Jiaotong University | Tao W.-Q.,Xian Jiaotong University
Applied Thermal Engineering

In order to study the coupling mechanism between ash deposition and dew point corrosion, five kinds of tube materials frequently used as anti-dew point corrosion materials were selected as research objects. Dew point corrosion and ash deposition experiments were performed with a new type experimental device in a Chinese thermal power plant. The microstructures of the materials and the composition of ash deposition were analyzed by X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS). The results showed that the ash deposition layer could be divided into non-condensation zone, the main condensation zone and the secondary condensation zone. The acid vapor condensed in the main condensation zone rather than directly on the tube wall surface. The dew point corrosion mainly is oxygen corrosion under the condition of the viscosity ash deposition, and the corrosion products are composed of the ash and acid reaction products in the outer layer, iron sulfate in the middle layer, and iron oxide in the inner layer. The innermost layer is the main corrosion layer. With the increase of the tube wall temperature, the ash deposition changes from the viscosity ash deposition to the dry loose ash deposition, the ash deposition rate decreases dramatically and dew point corrosion is alleviated efficiently. The sulfuric dew point corrosion resistance of the five test materials is as follows: 316L > ND > Corten>20G > 20# steel. © 2012 Elsevier Ltd. All rights reserved. Source

Li M.,Xian Jiaotong University | Wang J.,Xian Jiaotong University | He W.,Xian Jiaotong University | Gao L.,Thermal Power Research Institute | And 4 more authors.
Renewable Energy

Higher efficiencies and optimal utilization of geothermal energy require a careful analysis of Organic Rankine Cycle (ORC) which is suitable for converting electric power from low-temperature heat sources. The objective of this study is to experimentally analyze the effect of varying working fluid mass flow rate and the regenerator on the efficiency of the regenerative ORC operating on R123. As R123 presents a low boiling point temperature (27.82 °C), a technology was invented to address the leakage issue when transferring R123 between the inside and outside of the regenerative ORC system. A specially manufactured throttle valve was adopted in the bypass subsystem to protect the turbine during the starting and closing processes and a novel phenomenon was discovered during the test. A preliminary test of the system was conducted with a geothermal source temperature of 130 °C. The experimental results show that the power output is 6 kW and the regenerative ORC efficiency is 7.98%, which is higher than that of the basic ORC by 1.83%. © 2013 Elsevier Ltd. Source

Zhang Y.,Thermal Power Research Institute | Zhang Y.,Xian Jiaotong University | Che D.,Xian Jiaotong University
Numerical Heat Transfer; Part A: Applications

A numerical study in a rectangular channel is performed to investigate the effect of roughness of a transverse V-shaped groove on flow and wall mass transfer characteristics. The study is completed by four rough walls with different groove sizes, and the Reynolds number spans from 103 to 105. The flow and concentration fields are obtained using a validated low Reynolds number k-ε turbulence model. The influences of Reynolds number, groove depth, and groove pitch on near-wall flow and wall mass transfer are discussed. The mass transfer boundary layer developments and local mass transfer coefficient distributions over different walls are presented. As the grooves become denser and shallower, the more augmentation of wall mass transfer rate is observed. However, increasing Reynolds number weakens the enhancement effect. The averaged Sherwood number is correlated as a function of Reynolds number and groove geometric parameters. © 2014 Taylor & Francis Group, LLC. Source

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