Compressed air and gas are the lifeline of power plants. Deficient or unstable supply of air and gas can result in huge costs and revenue losses of plants. Thus, the accurate determination of performance of the compressors plays important role in prediction of the plant performance. In order to provide reliable and low cost operation for end users, an uncertainty analysis of volume flow, pressure ratio, and power consumption have been investigated and implemented to accurately determine the effect of the compressors to the plant performance. Mathematical models for the uncertainty treatments are proposed based on the ASME test code, and both the systematic errors originating from the measurement instruments and random errors rooted from the raw data are taken into consideration. Moreover, the approach of the uncertainty propagation is also presented through data reduction equations in this paper to evaluate the final performance. Both the rigorous numerical model and sophisticated data acquisition system instrumented in the test facility are employed to conduct the uncertainty analysis for a multi-stage centrifugal compressor. Comprehensive error sources such as ambient conditions, inter-stage pressures and temperatures, and rotational speeds are identified and studied for the final tolerance of the pressure ratio and power consumption of the whole compressor. The test uncertainty results of the compressor can help to improve the power plant field design and demonstrate quality assurance and quality control. Moreover, the tolerance analysis introduced in this paper can be extended to each component of the power plant system to optimize the performance of the whole power plant.

We propose a novel scheme to handle moving boundaries, both straight and curved, within the lattice Boltzmann method (LBM). In this scheme, which is broadly based on the Chapman–Enskog expansion, the fictitious distributions are constructed exactly on the moving boundary. This is in contrast to existing methods where such distributions are constructed on neighboring nodes which may not lie on the moving boundary. The post-collisional distributions on the fluid nodes near the moving boundary are then constructed using first- or second-order interpolations. The proposed scheme also overcomes the requirement to have separate interpolation formulations for different values of the intersection parameter. Several validation tests presented here indicate improved accuracy and numerical stability, compliance with Galilean invariance principle, an ability to preserve the geometric fidelity of curved surfaces.

Humidification dehumidification desalination system has shown advantages to satisfy small scale freshwater demand. In this paper, an air-heated humidification dehumidification desalination system powered by low grade waste heat, coupled with plate heat exchangers, is constituted. Working mechanisms of the air-heated HDH desalination system are revealed, and performance for both the humidification dehumidification desalination unit and the plate heat exchangers is obtained and analyzed based on the established mathematical models. Entropy generation of both the components and the whole humidification dehumidification desalination system is calculated to judge the feasibility of the system cases and demonstrate the energy loss. Simulation results show that despite the top value of the gained-output-ratio, 3.51, at the balance condition of the dehumidifier with a negative specific entropy generation of the dehumidifier, the actual maximum value is 3.04 when the mass flow rate ratio between the seawater and the dry air is (m) over dot/(m) over dot(da) = 1.28. Based on the elevation of the heat transfer rate and the descendant trend of the heat transfer coefficient, the heat transfer area of the plate heat exchangers rises from A = 5.25 m(2) to A = 15.90 m(2). Furthermore, it is summarized that the pressure drop of the plate heat exchangers will result in a very limited adverse influence on the energy utilization efficiency of the whole humidification dehumidification desalination system. (C) 2016 Elsevier Ltd. All rights reserved.

Humidification dehumidification (HDH) technology was well applied to produce freshwater in the desalination system. However, besides the demand of freshwater, power is also required simultaneously in most situations. In the paper, a novel water-power cogeneration plant (WPCP) based on the HDH desalination system coupled with the organic Rankine cycle (ORC) is proposed. Energy analysis for the proposed combined system at different appointed operation parameters is achieved, and the corresponding performance correlation between the HDH desalination and ORC power system are revealed. It is verified that the production of freshwater and electricity can be gained synchronously in the suggested novel platform, and the performance of the whole system is really sensitive to the operation parameters of the HDH desalination system. It is found that after the regulation of the operation pressure, p, and the seawater temperature at the outlet of the seawater heater, T-sw,T-2, for the HDH desalination from p = 0.1 MPa, T-sw,T-2 = 353.15 K to p= 0.3 MPa, T-sw,T-2 = 383.15 K, a maximum elevation, 25.46 kg h(-1) for the freshwater production, 4.17 kW for the electricity and 2% for the extended gained output ratio (EGOR) is obtained. Furthermore, owing to the asynchronism between the specific production and the final energy utilization efficiency, the balance should be optimized among the demand of the freshwater and power and the efficiency of the novel WPCP. (C) 2015 Elsevier Ltd. All rights reserved.

Industrial waste heat is effective to provide power for the desalination system to acquire distilled water. In this paper, exhaust gas is drawn into the plate heat exchangers (PHEs) to heat the circulated humid air within the humidification dehumidification (HDH) desalination unit. Based on the governing equations of the components and the fixed-effectiveness model, key parameters are prescribed to accomplish the performance analysis of the HDH desalination system, and the relevant recovery results of the waste heat are also attained. The simulation results present that the balance condition of the dehumidifier is inaccessible due to a negative specific entropy generation of the dehumidifier in spite of the obtained best performance at such point. It is summarized that high values of the component effectiveness and the initial temperature as well as the vacuum environment are beneficial to raise the performance of the desalination system and reduce the heat transfer surface area for the PHEs. Moreover, the elevation of the top temperature contributes to a slight elevation of the gained-output-ratio (GOR), while the relevant heat transfer surface area of the PHEs increases.

Humidification dehumidification (HDH) technology is an effective pattern to separate freshwater from seawater or brackish water. In this paper, a closed-air open-water (CAOW) desalination unit coupled with plate heat exchangers (PHEs) is applied to recover the waste heat from the gas exhaust. Sensitivity analysis for the HDH desalination unit as well as the PHEs from the key parameters including the top and initial temperature of the seawater, operation pressure, and the terminal temperature difference (TTD) of the PHEs are accomplished, and the corresponding performance of the whole HDH desalination system is calculated and presented. The simulation results show that the balance condition of the dehumidifier is allowed by the basic thermodynamic laws, followed by a peak value of gained-output-ratio (GOR) and a bottom value of total specific entropy generation. It is concluded that excellent results including the system performance, heat recovery effect and investment of the PHEs can be simultaneously obtained with a low top temperature, while the obtained desalination performance and the heat recovery effect from other measures are always conflicting. Different from other parameters of the desalination unit, the terminal temperature difference of the PHEs has little influences on the final value of GOR. (C) 2016 Elsevier Ltd. All rights reserved.

Particulate suspensions are common phenomena in industrial and biological fields. However, the fundamental understanding of the hydrodynamic interactions between the solid and fluid in the particulate suspensions needs to be further improved. The lattice Boltzmann method has been shown to be an effective numerical method to model various fluid flows, and exhibits good performance in dealing with boundary conditions, with straightforward and easy-to-implement methods for complex solid boundaries. However, most of the previous boundary conditions used for the moving complex surface are based on the half way bounce-back boundary condition, where the geometric integrity of the body cannot be maintained. In this dissertation, a new boundary condition based on the Chapman-Enskog expansion is proposed for the moving complex surface, where the precise shape of the body can be preserved during the calculation. Moreover, due to the second order accuracy of the Chapman-Enskog expansion when recovering the Navier-Stokes equation from the Boltzmann-BGK equation, the new boundary condition can maintain the same accuracy for the whole computational domain. Finally, this thesis provides the novel idea to construct a boundary condition without the limitation of being based on the information from the already existing lattice nodes.

The present study reports a novel concept of a direct solar thermal collector that harnesses the localized surface plasmon of metallic nanoparticles suspended in water. At the plasmon resonance frequency, the absorption and scattering from the nanoparticle can be greatly enhanced via the coupling of the incident radiation with the collective motion of electrons in metal. However, the surface plasmon induces strong absorption with a sharp peak due to its resonant nature, which is not desirable for broad-band solar absorption. In order to achieve the broad-band absorption, we propose a direct solar thermal collector that has four types of gold-nanoshell particles blended in the aquatic solution. Numerical simulations based on the Monte Carlo algorithm and finite element analysis have shown that the use of blended plasmonic nanofluids can significantly enhance the solar collector efficiency with an extremely low particle concentration (e.g., approximately 70% for a 0.05% particle volume fraction). The low particle concentration ensures that nanoparticles do not significantly alter the flow characteristics of nanofluids inside the solar collector. The results obtained from this study will facilitate the development of highly efficient solar thermal collectors using plasmonic nanofluids.

In this paper, a two-dimensional core-shell nanowire made of a dielectric core and metallic cladding is proposed for exciting the magnetic resonance on an isolated nanostructure. The key idea is to remove a small portion of the metallic cladding on the nanowire so that the incident magnetic field can be localized in the dielectric core. It is also found that the core-shell nanowire can support the localized surface plasmon, whose resonance frequency mainly depends on the thickness of the metallic cladding. The finite-difference time-domain method is employed to calculate the scattering cross-section of the proposed structure and the near-field distribution of the magnetic field at resonance conditions. The results obtained from this study will advance our fundamental understanding of the light-matter interaction at nanometer scales and facilitate the development of multi-dimensional metamaterials for subwavelength imaging.

A Chebychev spectral elements approximate solution of the acoustic propagation problem in subsonic pipe was introduced.The discretization was carried out based on spectral elements in space with sound-hard boundary on the rigid wall and sound-soft boundary at the inlet and outlet of the pipe.An implicit Newmark method was used for time marching.Gaussian perturbation as a test measure was calculated with good results obtained and the boundary reflections were analyzed as well.The absorbing boundary condition is suitable in static medium while losing some accuracy in subsonic flow.The numerical simulation of acoustic propagation with sixth order accuracy was implemented,and its results coincide well with those according to the linear acoustic theory,illustrating the high performance of spectral elements method in solving CAA problems.

Metal-enhanced fluorescence has been studied over the past three decades in order to improve fluorescence sensing and imaging techniques in microfluidics and medical diagnostics. However, most of previous studies were performed while precisely maintaining the distance between fluorophore and plasmonic nanoparticles. In the present study, we investigate the enhanced fluorescence from quantum dots (QDs) that are mixed with plasmonic nanoparticles, such as gold nanoshell (GNS), in the aqueous medium without confining the interparticle distance. Although the near-field interaction could not occur based on the estimated interparticle distance according to particle concentrations, the experimental results indicate that the QD fluorescence can be greatly enhanced. A Monte Carlo simulation revealed that there exists considerable probability that QDs can reach the near-field region of GNS due to the thermally induced Brownian motion.