The application of mini-hydrocyclones in the concentration of yeast suspensions

Small diameter hydrocyclones have had an increasing use in performing difficult separations between phases, due to the large centrifugal forces generated in them. The potential use of hydrocyclones in the concentration of microbial suspensions is attractive as they are continuous, high capacity devices requiring low maintenance while having the additional benefit in that they can be readily sterilised.Results are reported on the de-watering of Bakers' yeast in a 10 mm diameter hydrocyclone to quantify the separation process. The form of the model equation for recovery has been derived based on the non-equilibrium residence time theory. This is shown to represent experimental data in that increasing pressure and temperature exhibit a positive effect on both the recovery and the concentrating effect while an increase in the feed concentration exhibits a negative effect on these. In addition, the influence of cyclone geometry on the recovery and concentration ratio has been illustrated. Increasing the vortex diameter results in an increasing concentration ratio and a decreasing recovery. Increasing the diameter of the spigot shows the opposing trends.Typical results from a single stage separation combine a recovery of 60% with a concentration ratio of 1.25 and a recovery of 30% with a concentration ratio of 2.0. Concomitant improvement of the recovery and concentration ratio will be attainable through the use of multi-stage hydrocyclone circuits.     

GPPre: A Python-Based Tool in Grasshopper for Office Building Performance Optimization

With the development of the economic and low-carbon society, high-performance building (HPB) design plays an increasingly important role in the architectural area. The performance of buildings usually includes the building energy consumption, building interior natural daylighting, building surface solar radiation, and so on. Building performance simulation (BPS) and multiple objective optimizations (MOO) are becoming the main methods for obtaining a high performance building in the design process. Correspondingly, the BPS and MOO are based on the parametric tools, like Grasshopper and Dynamo. However, these tools are lacking the data analysis module for designers to select the high-performance building more conveniently. This paper proposes a toolkit “GPPre” developed based on the Grasshopper platform and Python language. At the end of this paper, a case study was conducted to verify the function of GPPre, which shows that the combination of the sensitivity analysis (SA) and MOO module in the GPPre could aid architects to design the buildings with better performance.     

Turbulence correction for thermal comfort calculation

Thermal comfort in ventilated spaces depends mainly on air temperature, air speed and turbulence intensity. Mean air speed is commonly measured with omnidirectional hot sphere sensors, whereas directionally sensitive measurement instruments and CFD-simulations normally give the mean velocity vector. The magnitude of the mean velocity vector in turbulent room air flows can be much lower than the mean air speed due to different time averaging processes. This paper studies the difference both experimentally and theoretically as a function of turbulence intensity. A correction method was developed for calculating estimates for omnidirectional mean air speed and turbulence intensity from directional air velocity data. The method can be applied to the calculation of draught risk and thermal comfort from CFD-simulation results.     

CFD simulation and experimental validation studies on hydrocyclone

Hydrocyclone is a key unit operation in mineral process industry and simulation of which using CFD techniques is gaining popularity in process design and optimization. The success of the simulation methodology depends primarily on how best the results are matching with the experimental values and the computational time it requires for obtaining such results. In the present investigation, attempts are made to develop a methodology for simulating the performance of hydrocyclone. Initial work included comparison of experimental and simulated results generated using different turbulence models i.e., standard k–ε, k–ε RNG and RSM in terms of water throughput and split with the help of suitably designed experiments. Among the three modeling methods, predictions using RSM model were found better in agreement with experimental results with a marginal error between 4% and 8%. Parametric studies have indicated that a decrease in the spigot opening increased the upward vertical velocity of water more compared to a decrease in the downward vertical velocity. An increase in the inlet pressure has increased the axial velocities of water in both the upward and downward directions and increased the mass flow rates through the cyclone. An increase in the inlet pressure has also increased the static pressure differential along the radius within the cyclone body and hence more water split into overflow. Further, an increase in the inlet pressure has also increased the tangential velocities and reduced the cyclone cut size. The simulated particle distribution values generated using the particle injection technique are found matching with the experimental results while achieving cut sizes between 4.9 and 14.0 μm.     

Prediction of building envelope performance in the design stage: an application for office buildings

Building envelope should provide visual, thermal and acoustical comfort in accordance with the function of the room. The material properties of the translucent-window- and opaque components-wall- of the building envelope and the ratio of these components are effective in the establishment of comfort conditions in an interior. The perfection of the building envelope design is highly related to the consideration of all parameters together for visual, thermal and acoustical comfort.In this article, at first basic design process to predict the building envelope providing visual, thermal and acoustical comfort, namely “optimum building envelope” is explained, then the used methodologies and some of the results of a research project named “Optimum building envelope design in terms of visual, thermal and acoustical comfort in offices” are presented.     

应用Web标注技术的建筑图像语义采集方法

为解决建筑师难以快速地从互联网中检索到符合创作需求的建筑图像的问题,提出了应用Web标注技术的建筑图像语义采集方法.首先,从建筑学角度界定了建筑图像及建筑图像语义的概念和类型;其次,给出了该方法的总体框架和操作流程;最后,以著名建筑网站为例进行案例演示,验证了该方法的可行性和有效性.操作流程细分为3个步骤,以人工添加和在线学习的方式建立建筑语义词典;运用数据采集软件,从建筑图像所在网页中分别采集图像名称、图像注释、图像周围文本、所在网页标题、所在网页正文、图像超链接网页标题6项图像相关文本;根据图像语义提取规则,从上述文本中提取建筑图像语义,与图像文件建立关联后存储到建筑图像数据库.案例检验结果表明,该方法是可行的,具有较强的操作性,能够自动、批量地从互联网中下载建筑图像,并采集图像名称、图像类别、图像主题、项目名称、项目类型等30多项特征,有效地克服了建筑图像查询效率较低的问题,进而提升了建筑师运用互联网图像进行创作的能力.     

基于决策树分类的可拓建筑策划预测方法

为提升建筑师在策划过程中科学预测的能力,提出了一种基于决策树分类的可拓建筑策划预测方法。首先,运用数据采集软件批量采集互联网中的建筑案例数据,将数据预处理后存储至建筑案例库中;其次,通过评价特征选取、评价信息元集生成、决策树构建等步骤,获得决策树模型;最后,运用该模型预测当前策划项目的性能指标是否满足要求,并给出不满足要求情况下性能指标变换的途径。案例检验表明,该方法能有效提高建筑师运用互联网数据的能力,能够挖掘决策树分类知识,从而加速计算机辅助可拓建筑策划的进程。     

Refinements of empirical models to forecast the shear strength of persistent weak snow layers: PART B: Layers of surface hoar crystals

Buried layers of surface hoar often release skier-triggered avalanches in the Columbia Mountains of Canada and their shear strength can be used to assess the stability of a slab overlaying these layers. In 2001 Chalmers introduced an Interval Model to calculate the shear strength of layers of surface hoar based on manual snowprofile observations. We refined his model by adjusting the measured shear strength for the normal load and included only data points where the weak layer depth did not exceed 100 cm to better account for skier triggering. Further, we used average and daily loading rates as well as a regression analysis to determine the best estimate of the shear strength change. Our final Forecasting Model used a multivariate regression to calculate the shear strength on days with snowprofile observations and as well as average and daily loading rates to forecast the shear strength on days without manual snowprofile observations. The performance of the model (r²) was 0.71 and 0.63 using average and daily loading rates, respectively. A companion paper, Part A, develops a forecasting model for weak layers of faceted crystals.     

Experimental investigation and modelling of a buoyant attached plane jet in a room

Buoyant attached jets are widely used in various types of supply air devices especially in office buildings. This study focuses on a two-dimensional cooled attached jet characteristic, including mean flow field structure, specification of the jet regions and maximum velocity decay. A new superimposing model is derived to predict the maximum velocity decay and validated by measurement results. The measurement results demonstrate that the intermediate region of a buoyant jet does exist when an inner layer extends downstream of the jet slot. In addition, by assuming that the buoyant force is the main extra force on the jet flow in the acceleration process, the superimposing model predicted the maximum velocity decay with precise accuracy in a Reynolds number range of 667–4000, based on slot heights of 20 and 30 mm and slot velocities of 0.50, 1.00 and 2.00 m/s. At a distance of 1000 mm from the slot, the velocity profile displays a self similarity character like an isothermal turbulent jet. In the final region, where the buoyancy flux completely dominates the jet, the jet behaved like a plume with an unstable flow field.