Modelling of a Superheater Heat Exchanger with Complex Flow Arrangement Including Flow and Temperature Maldistribution

A network approach was used to develop a thermofluid process model of a cross-flow primary superheater heat exchanger with complex flow arrangement in the convective pass of a coal-fired boiler. The model solves the transient one-dimensional forms of the conservation equations for mass, energy, and momentum, combined with the applicable closure relations, boundary values, and initial values. The dual-tube 12-pass superheater was discretized along the flue gas flow path as well as along the steam flow path. The model accounts for the convective thermal resistance on the steam side, the conductive thermal resistances of the tube wall, and scaling or fouling on the tube walls, as well as the convective and radiative thermal resistances on the flue gas side. The model was qualitatively validated using real plant data and for reference purposes also systematically compared to conventional lumped parameter models. The ability of the model to analyze the effect of the ramp rate during load changes on the tube metal temperature was demonstrated, as well as the ability to determine the maldistribution of flow and temperature on the steam and flue gas sides. Models such as this can be employed to study complex thermofluid process phenomena that may occur during intermittent, transient, and low-load operation of power plants. This could form the basis for improving operations and for the development of advanced tools for online process condition monitoring.     

上海住宅发展的主要特点--第四届上海优秀住宅评选综述

两年一届的“上海市优秀住宅”评选是唯一由政府支持,行业协会主办的住宅评选活动,遵循着公正、公平、公开和易操作的原则。今年开展的第四届优秀住宅评选,有234个项目、666个单项参评,覆盖了高、中、低各个层次,代表当前上海住宅发展的总体水平。历时夏、秋、冬三季,经20多位参评的上海著名资深专家现场踏勘,多次审核、几轮刷选,最后有13个项目获得综合金奖,有32个项目获得综合银奖,有15个项目获得优秀配套房奖,有6个项目获得优秀村镇住宅奖。参加此次活动的所有楼盘整体品质较高,这些楼盘在满足人居环境功能要求的同时,注重自然生态环境的…     

FWT2D: A massively parallel program for frequency-domain full-waveform tomography of wide-aperture seismic data—Part 1: Algorithm

This is the first paper in a two-part series that describes a massively parallel code that performs 2D frequency-domain full-waveform inversion of wide-aperture seismic data for imaging complex structures. Full-waveform inversion methods, namely quantitative seismic imaging methods based on the resolution of the full wave equation, are computationally expensive. Therefore, designing efficient algorithms which take advantage of parallel computing facilities is critical for the appraisal of these approaches when applied to representative case studies and for further improvements. Full-waveform modelling requires the resolution of a large sparse system of linear equations which is performed with the massively parallel direct solver MUMPS for efficient multiple-shot simulations. Efficiency of the multiple-shot solution phase (forward/backward substitutions) is improved by using the BLAS3 library. The inverse problem relies on a classic local optimization approach implemented with a gradient method. The direct solver returns the multiple-shot wavefield solutions distributed over the processors according to a domain decomposition driven by the distribution of the LU factors. The domain decomposition of the wavefield solutions is used to compute in parallel the gradient of the objective function and the diagonal Hessian, this latter providing a suitable scaling of the gradient. The algorithm allows one to test different strategies for multiscale frequency inversion ranging from successive mono-frequency inversion to simultaneous multifrequency inversion. These different inversion strategies will be illustrated in the following companion paper. The parallel efficiency and the scalability of the code will also be quantified.     

FWT2D: A massively parallel program for frequency-domain full-waveform tomography of wide-aperture seismic data—Part 2: Numerical examples and scalability analysis

This is the second paper in a two-part series that describes a massively parallel code that performs 2D full-waveform inversion of wide-aperture seismic data for imaging complex structures. We present several numerical validation of the full-waveform inversion code with both canonical and realistic synthetic examples. We illustrate how different multiscale strategies can be applied by either successive mono-frequency inversions or simultaneous multifrequency inversions and their impact on the convergence and the robustness of the inversion. We present a scalability analysis using a real marine data set recorded by a dense array of ocean bottom seismometers to image the crustal structure of a subduction zone. We obtained a speedup of 20 when using 50 processes on a PC cluster which allowed us to iteratively invert 13 frequencies of the full data set in less than 2 days. This computational performance will allow in the future more extensive analysis of full-waveform tomography methods when applied to representative case studies or when considering 3D geometries.     

Enrichment of salmon oil with n‐3 PUFA by lipolysis,filtration and enzymatic re‐esterification

Selective enzymatic hydrolysis of salmon oil extracted without solvent from by‐products was carried out under mild conditions, using a stereospecific sn‐1, sn‐3 lipase Novozyme^®. A modification of the lipid class composition was obtained by controlling the degree of hydrolysis (40%, 24 h). The mixture of acylglycerols and free fatty acids was submitted to a filtration step to retain in the retentate most of the saturated fatty acids, with melting peaks ranging from ‐31.9 °C to +14.7 °C obtained by differential scanning calorimetry. This step allowed a significant increase of polyunsaturated fatty acids (PUFA) from 39.2 mol‐% in the crude oil to 43.3% in the permeate. The remaining free fatty acids in the permeate (20.2 wt‐%) was re‐esterified with an immobilized 1, 3‐specific lipase IM60. Acylglycerols synthesis reached 90% in optimized conditions. After 48 h of reaction, the distribution of monoacylglycerols, diacylglycerols and triacylglycerols was 22.1, 28.7, 43.4 (w/w), respectively. The re‐esterification step did not modify the PUFA content obtained after membrane filtration.