Thermodynamic investigation of an integrated solar combined cycle with an ORC system

An integrated solar combined cycle (ISCC) with a low temperature waste heat recovery system is proposed in this paper. The combined system consists of a conventional natural gas combined cycle, organic Rankine cycle and solar fields. The performance of an organic Rankine cycle subsystem as well as the overall proposed ISCC system are analyzed using organic working fluids. Besides, parameters including the pump discharge pressure, exhaust gas temperature, thermal and exergy efficiencies, unit cost of exergy for product and annual CO2-savings were considered. Results indicate that Rc318 contributes the highest exhaust gas temperature of 71.2℃, while R113 showed the lowest exhaust gas temperature of 65.89 at 800 W/m2, in the proposed ISCC system. The overall plant thermal efficiency increases rapidly with solar radiation, while the exergy efficiency appears to have a downward trend. R227ea had both the largest thermal efficiency of 58.33% and exergy efficiency of 48.09% at 800W/m2. In addition, for the organic Rankine cycle, the exergy destructions of the evaporator, turbine and condenser decreased with increasing solar radiation. The evaporator contributed the largest exergy destruction followed by the turbine, condenser and pump. Besides, according to the economic analysis, R227ea had the lowest production cost of 19.3 $/GJ

Performance prediction of the combined cycle power plant with inlet air heating under part load conditions

A combined cycle power plant with inlet air heating (CCPP-IAH) system is proposed to solve the problems of ice and humidity blockages in winter climate. The performance of the CCPP-IAH system under part load conditions is analyzed via both experimental and simulation methods. The application of the inlet air heating technology significantly improves the part load efficiency and enhances the operational safety of the combined cycle power plant under complex meteorological conditions. Results show that a higher inlet air temperature will contribute a lower gas turbine thermal efficiency for proposed system. However, the heated inlet air by the recovered energy in heat recovery steam generator raises efficiencies for both the heat recovery steam generator and the overall system. The fuel consumption drops by 0.02 kg/s and 0.03 kg/s under the power load of 65% and 80%, respectively. The inlet air humidity decrease to 30% under the heated inlet air temperature of 303 K. Moreover, the exergy destruction for both Brayton cycle part and Rankine cycle part decrease with the inlet air temperature increasing. The daily fossil fuel will raise up to 2.9 ton/day and to 5.1 ton/day under the power load of 65% and 80%, respectively. The annual economic benefit from energy saving is more than $ 5.88 × 105 and the payback period is less than 3 years

Land snail diversity in central China: revision of Laeocathaica Möllendorff, 1899 (Gastropoda, Camaenidae), with descriptions of seven new species

Central China harbors the native dart-sac-bearing camaenids Laeocathaica. The genus is revised and seven new species are proposed based on museum material and newly collected specimens. This work confirmed that most Laeocathaica species have restricted habitats. The comparison of the dart sac apparatus among the dart-sac-bearing camaenid genera indicated the importance of the presence of the proximal accessory sac that might be analogous to the membranous/muscular sac surrounding the proximal dart sac and/or the distal region of the vagina near the atrium, which also plays a significant role in the diagnosis of Laeocathaica species based on its number, symmetry and position on the dart sac. Species with similar shell morphology were studied using geometric morphometric methods to detect variations in shell shape. A molecular phylogenetic analysis based on 16S and ITS2 sequence data of partial Laeocathaica species and many other dart-sac-bearing taxa suggested that Laeocathaica might be monophyletic. Furthermore, the present phylogeny indicated that Stilpnodiscus, Cathaica, Bradybaena, and Pseudobuliminus might be polyphyletic and therefore the taxonomy of dart-sac-bearing camaenids in this region requires a thorough revision. This work reconfirms that the Southern Gansu Plateau is important as a hotspot for malacodiversity conservation on the Chinese mainland

Advanced Thermodynamic Analysis Applied to an Integrated Solar Combined Cycle System

The variation performance of integrated solar combined cycle (ISCC) is presented using energy, conventional exergy and advanced exergy analysis methods to provide information about exergy destruction of components and efficiencies of overall plant. Moreover, the theory of dividing the exergy destruction of main components into unavoidable/avoidable and exogenous/endogenous parts allows for further understanding the real potentials for improving. Besides, the exergy destruction rate and exergy efficiency of components as well as overall plant were hourly analyzed within a typical day. Results indicate the exergy destruction rate of overall system drops from 49.79% to 44.65% in summer and decreases from 49.79% to 47.59% in winter. As the solar irradiation intensity rises, the solar field efficiency reaches to 42.16% in winter and 47.5% in summer. The solar-to-electric energy efficiency gets to 13.69% in winter and 15.46% in summer. In addition, with the increase of solar energy input to the ISCC system, the exergy destruction of Brayton cycle components decreases; however, the exergy destruction of Rankine cycle components increases. Furthermore, the exergy destruction of solar field has a large extended from 14.55 MW to 58.03 MW. Moreover, the heat recovery steam generator (HRSG) and the steam turbines have the largest exergy destruction rate of 11.26% and 13.63% at 15:00 p.m

Determination of Key Technical Parameters in the Study of New Pressure Sealing Technology for Coal Seam Gas Extraction

Coal is affected by the concentrated stress disturbance of mining, the disturbance of drilling hole formation, and the concentrated stress of coal shrinkage and splitting of gas desorption from the hole wall; these result in a large number of secondary cracks that collect and leak gas. As a result, it is difficult for the coal seam sealing process to meet engineering quality sealing requirements, which results in problems such as low gas concentration during the extraction process. In this paper, based on the analysis of coal pore and fissure characteristics, and in view of the current situation of gas drainage and sealing in this coal seam, combined with the existing grouting and sealing technology, it is proposed to use pressure grouting and sealing to realize the sealing of deep coal bodies in the hole wall. According to the field conditions, the experimental pressure sealing parameter index is as follows: theoretical sealing length L1 = 9.69 m, the sealing length L2 = 13.98 m is verified, and the final sealing length is determined to be 15 m; the sealing radius is determined to be 0.6 m; the cement slurry was prepared on site with a water: cement ratio of 2:1; PG = 0.43 MPa was calculated; the range of the slurry diffusion radius R was 93.4–176.6 cm; the grouting pressure was determined to be 0.516 MPa. Field application practice has proved that: (1) Under the same drilling parameters and sealing parameters, the gas drainage effect of drilling with pressure sealing is 2.3 times higher than that without pressure sealing; (2) Using traditional sealing technology for drilling holes, the gas extraction concentration is far lower than the sealing operation effect of using the pressure sealing process; (3) Reasonably extending the length of the gas extraction drilling and sealing is a basic guarantee for realizing a substantial increase in the gas extraction concentration; (4) Sealing with pressure leads to a reliable and stable hole process

Efficacy and safety of acupuncture in the treatment of postherpetic neuralgia: a protocol for Systematic Review and Network Meta-analysis

Abstract Background It is simple, convenient, inexpensive, proven, extensive, and safe for acupuncture in the treatment of postherpetic neuralgia (PHN). However, there are no comparisons between various acupuncture therapies that can directly and effectively provide specific guidance to clinicians. The development of a guideline for the optimization of acupuncture for PHN is of great importance for the development of clinical acupuncture. Therefore, we attempted to design a study protocol for a network meta-analysis of randomized controlled trials (RCTs) of acupuncture for PHN to provide evidence to support the treatment of acupuncture for PHN. Methods A search of eight databases, Chinese Scientific Journal Database, China National Knowledge Infrastructure Database, Wanfang，China Biomedical Literature Database, PubMed, Cochrane Library, Embase, and Web of Science, was conducted to collect RCTs about acupuncture for PHN. RevMan 5.3 and Stata 14.0 software were used for data analysis. Results This meta-analysis will provide additional and more robust evidence for acupuncture treatment of PHN. Our findings will assist clinicians in making treatment decisions. Conclusion This study will provide comprehensive and reliable evidence-based evidence for the treatment of PHN with acupuncture

Thermodynamic and Economic Analysis of an Integrated Solar Combined Cycle System

Integrating solar thermal energy into the conventional Combined Cycle Power Plant (CCPP) has been proved to be an efficient way to use solar energy and improve the generation efficiency of CCPP. In this paper, the energy, exergy, and economic (3E) methods were applied to the models of the Integrated Solar Combined Cycle System (ISCCS). The performances of the proposed system were not only assessed by energy and exergy efficiency, as well as exergy destruction, but also through varied thermodynamic parameters such as DNI and Ta. Besides, to better understand the real potentials for improving the components, exergy destruction was split into endogenous/exogenous and avoidable/unavoidable parts. Results indicate that the combustion chamber of the gas turbine has the largest endogenous and unavoidable exergy destruction values of 202.23 MW and 197.63 MW, and the values of the parabolic trough solar collector are 51.77 MW and 50.01 MW. For the overall power plant, the exogenous and avoidable exergy destruction rates resulted in 17.61% and 17.78%, respectively. In addition, the proposed system can save a fuel cost of 1.86 $/MW·h per year accompanied by reducing CO2 emissions of about 88.40 kg/MW·h, further highlighting the great potential of ISCCS

A Study of Constitutive Model of Rock Damage under the Joint Effect of Load and Moisture

To study the mechanical damage characteristics of rock under the effect of subversion, a series of mechanical experiments, including both uniaxial and triaxial mechanical compression experiments under various levels of water content were performed. In this study, researchers investigate the impact of water content on the mechanical characteristics of rock, based on the compliance of the rock damage variants to the Weibull statistic distribution, and Drucker–Prager strength rule, aiming to construct a constitutive model under the joint effect of load and moisture. In addition, the established constitutive model is tested in the experiment. According to the test results, during the initial phase of the submersion, the water content in the rock increases following the exponential function until reaching the threshold. The water content remains stable after the threshold. Under the uniaxial and triaxial loads, the damage detected in the rock and the elasticity modulus decreases linearly as the water content increases. The rock’s mechanical parameters and the damage evolution rate are significantly impacted by the surrounding pressure. As the surrounding pressure increases, the weakening effect of the water in the rock decreases. The theoretic curves developed to describe the rock damage under the joint effect of the water and load are consistent with the curves drafted based on the test, indicating that the constitutive model can accurately describe the stress and strain behaviors of rock under various water contents and loading conditions