Search results

The membrane wall is one of the most important components in the boiler industry and numerous studs are welded on its surface. The membrane wall welding still remains a sector intensive in the manual and arduous works. This paper aims to propose a dual-robot system to automatically weld studs on the membrane wall.

In this paper, the authors proposed a dual-robot stud welding system for membrane walls. First, the membrane wall is divided into several zones and the welding paths are planned. Then, the pose of the pipes is calculated based on the data measured by light section sensors. The planned paths are compensated by the pose. Finally, the robots weld studs based on the compensated paths.

The method effectively eliminates manufacturing errors and welding distortions. The system can weld straight type and L-type membrane walls with high efficiency, high quality and high accuracy.

The system can weld straight type and L-type membrane walls with high efficiency and high quality. Experiments were performed in a factory to demonstrate the practicability of the method. The dual-robot system with two welding machines has approximately twice the efficiency of the manual welder with only one welding machine. The quality and accuracy of robot welding systems are higher than that of manual welding.

THE Aerotech Exhibition held in conjunction with the Congress at Birmingham was attended by companies and establishments with a range of products and services. Many of these related to the achievement and maintenance of high standards in components and assemblies and particular interest was attached to the display of expertise shown by the National NDT Centre at Harwell. The operations at the Centre cover research and development and inspection instruments as well as services and consultancies, the first of these often involving the design of special purpose inspection equipment.

The purpose of the present paper is to model a cavity, which is equally divided vertically by a thin, flexible membrane. The membranes are inevitable components of many engineering devices such as distillation systems and fuel cells. In the present study, a cavity which is equally divided vertically by a thin, flexible membrane is model using the fluid–structure interaction (FSI) associated with a moving grid approach.

The cavity is differentially heated by a sinusoidal time-varying temperature on the left vertical wall, while the right vertical wall is cooled isothermally. There is no thermal diffusion from the upper and lower boundaries. The finite-element Galerkin technique with the aid of an arbitrary Lagrangian–Eulerian procedure is followed in the numerical procedure. The governing equations are transformed into non-dimensional forms to generalize the solution.

The effects of four pertinent parameters are investigated, i.e., Rayleigh number (104 = Ra = 107), elasticity modulus (5 × 1012 = E_T = 1016), Prandtl number (0.7 = Pr = 200) and temperature oscillation frequency (2p = f = 240p). The outcomes show that the temperature frequency does not induce a notable effect on the mean values of the Nusselt number and the deformation of the flexible membrane. The convective heat transfer and the stretching of the thin, flexible membrane become higher with a fluid of a higher Prandtl number or with a partition of a lower elasticity modulus.

The authors believe that the modeling of natural convection and heat transfer in a cavity with the deformable membrane and oscillating wall heating is a new subject and the results have not been published elsewhere.

The purpose of this paper is to propose a methodology for evaluating the hygrothermal performance of framed wall assemblies based on design limits. This methodology allows designers to evaluate wall assemblies based on their absolute performance rather than relative performance which is typically done for most hygrothermal analysis.

The approach in developing this methodology was to evaluate wall assemblies against three typical design loads (e.g. air leakage, construction moisture, rain penetration) and determine limits in minimum insulation ratio, maximum indoor humidity and maximum rain penetration rates. This analysis was performed at both the field area of the wall and at framing junctions such as window sills.

The findings in this paper shows example design limits for various wall assemblies in heating-dominated climates in North America. Design limits for wall assemblies with moisture membranes of different vapour permeance are provided for both the field area of the wall and at window sills. Discussions about the importance of 2D hygrothermal simulation and performance of vapour permeable sub-sill membranes are also provided.

This framework of hygrothermal analysis will enable designers to make better decisions when designing framed wall assemblies suitable to the local climate and interior specifications for their projects. It will also enable the development of a design tool that will allow designers to visually see the implications of certain design decisions and filter out designs that do not meet their design conditions.

Cracks in the roof parapet wall and damage to the waterproofing membrane are the common defects of roof construction that require frequent maintenance. This paper seeks to review the common defects of roof construction of medium‐rise buildings in sub‐tropical climates.

The research reported was carried out by the survey and analysis of 20 case study buildings. The modes of rooftop parapet wall dislocation are studied and the effects of thermal expansion and end conditions of the parapet wall on the damage to the waterproofing membrane are analysed.

Parapet wall dislocation failure is dependent on whether the ends are hinged or fixed. Failure usually leads to tearing of the waterproofing membrane.

Modification to the roof parapet wall design and to the selection of construction materials is suggested.

The modes of failure and proposed modification will be of interest to designers and those responsible for the maintenance of flat‐roofed buildings in sub‐tropical climates.

The permeate flux in microfiltration (MF) declines sharply with time due to membrane fouling, which seriously restricts its use in industrial applications. The purpose of this paper is to investigate particles deposition in MF processes, and propose a three-dimensional numerical model that focuses on particle-fluid flow and considers both permeable boundary conditions and cake deposition.

The two-ways coupling model was solved using Euler-Lagrange methods in which the suspended particle was traced by a hard sphere model and the fluid was simulated using large eddy model.

The numerical results predicted based on this model demonstrated the permeate flux increased as trans-membrane pressure and inlet velocity increased but decreased with an increase in feed concentration.

Good agreement was observed between the values obtained with the model and experimental values from the literature. The error is less than 20 per cent both permeate flux and cake thickness. In addition, a precise visualisation of cake morphology with filtration time was provided.

These analyses allowed for an estimation of the three-dimensional motion of suspended particles in turbulent flow. It saves manpower and financial resources for experiment, which possess important theoretical and industrial significance.

A mathematical model to predict the concentration polarisation in nanofiltration/reverse osmosis is described. It incorporates physical modelling for mass transfer, laminar hydrodynamics and the membrane rejection coefficient. The SIMPLE algorithm solves the discretised equations derived from the governing differential equations. The convection and diffusive terms of those equations are discretised by the upwind, the hybrid and the exponential schemes for comparison purposes. The hybrid scheme appears as the most suitable one for the type of flows studied herein. The model is first applied to predict the concentration polarisation in a slit, for which mathematical solutions for velocities and concentrations exist. Different grids are used within the hybrid scheme to evaluate the model sensitivity to the grid refinement. The 55×25 grid results agree excellently for engineering purposes with the known solutions. The model, incorporating a variation law for the membrane intrinsic rejection coefficient, was also applied to the predictions of a laboratory slit where experiments are performed and reported, yielding excellent results when compared with the experiments.

The purpose of this paper is to first present the key features of the fuzzy logic (FL) approach as a cost-effective technique in simulations of complex systems and then demonstrate the formulation and application of the method.

The FL approach is used as an alternative method of data handling, considering the complexity of analytical and numerical procedures and high costs of empirical experiments. The distance from gas distributor, the temperature and the voidage of the bed, flue gas velocity and the load of the boiler are the input parameters, whereas the overall heat transfer coefficient for the membrane walls constitutes the output. Five overlapping sigmoid and constant linguistic terms are used to describe the input and the output data, respectively. The Takagi–Sugeno inference engine and the weighted average defuzzification methods are applied to determine the fuzzy and crisp output value, respectively.

The performed FL model allows predicting the bed-to-wall heat transfer coefficient in a large-scale 670 t/h circulating fluidized bed (CFB) boiler. The local heat transfer coefficients evaluated using the developed model are in very good agreement with the data obtained in complementary investigations.

The performed model constitutes an easy-to-use and functional tool. The new approach can be helpful for further research on the bed-to-wall heat transfer coefficient in the CFB units.

This paper aims to numerically study the effects of boundary conditions, pre-stress, material constants and thickness on the dynamic performance of a wrinkled thin membrane.

Based on the stability theory of plates and shells, the dynamic equations of a wrinkled thin membrane were developed, and they were solved with the Lanczos method

The effects of wrinkle-influencing factors on the dynamic performance of a wrinkled membrane are determined by the wrinkling stage. The effects are prominent when wrinkling deformation is evolving, but they are very small and can hardly be observed when wrinkling deformation is stable. Mode shapes of a wrinkled membrane are sensitive to boundary conditions, pre-stress and Poisson’s ratio, but its natural frequencies are sensitive to all these five factors.

The research work in this paper is expected to help understand the dynamic behavior of a wrinkled membrane and present access to ensuring its dynamic stability by controlling the wrinkle-influencing factors.

Very few documents investigated the dynamic properties of wrinkled membranes. No attention has yet been paid by the present literature to the global dynamic performance of a wrinkled membrane under the influences of the factors that play a pivotal role in the wrinkling deformation. In view of this, this paper numerically studied the global modes and corresponding frequencies of a wrinkled membrane and their variation with the wrinkle-influencing factors. The results indicate that the global dynamic properties of a wrinkled membrane are sensitive to these factors at the stage of wrinkling evolution.