Numerical analysis of fin-tube plate heat exchanger by using CFD technique

Ahmed F. Khudheyer and Mahmoud Sh. Mahmoud

Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a two-row plain fin-and-tube heat exchanger using Open FOAM, an open-source CFD code. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created, meshed, calculated, and post-processed using open source software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-epsilon, and Menter SST k-omega), with steady-state solvers to calculate pressure drop, flow, and temperature fields. Model validation is carried out by comparing the simulated case friction factor f and Colburn factor j to experimental results from the literature. For friction factor determination, little difference is found between the flow models simulating laminar flow, while in transitional flow, the laminar flow model produced the most accurate results and the k-omega SST turbulence model was more accurate in turbulent flow regimes. The most accurate simulations for heat transfer in laminar flow are found using the laminar flow model, while heat transfer in transitional flow is best represented with the SST k-omega turbulence model, and heat transfer in turbulent flow is more accurately simulated with the k-epsilon turbulence model. Reasonable agreement is found between the simulations and experimental data, and the open-source software has been sufficient for simulating the flow fields in tube-fin heat exchangers.

Informative binarization based on unsharp masking

Yumnam Kirani Singh

In the existing methods of binarization, most of the edge information is lost and the resulted binary image gets blurred. Edges carry most of the information in an image. If we can preserve or retain most of the edge information in a binary image, the image will be informative and look natural. To preserve edge information in a binary image, the edges in the grey image must be enhanced using some effective unsharp masks. We propose a new method of generating unsharp masks, which can be used to enhance the edges in an image effectively. Once an effective unsharp mask is obtained, we apply it on an input grey image to get enhance the edges in the image. The edge enhanced grey image is binarized to give informative binary image. The informative binary images look better and more informative as compared with binary images obtained using by popular Otshu’s method.

Garnet group minerals from the amphibolite facies metamorphic rocks of Krivaja-Konjuh ultramafic massif in Bosnia and Herzegovina

M. Operta, S. Hyseni, D. Balen, S. Salihović and B. Durmishaj

In Bosnia and Herzegovina’s ophiolite zone there are six different ophiolite complexes including Krivaja-Konjuh ultramafic massif. In the south-eastern parts of the massif, the basement is built of different varieties of amphibolites with subordinate occurrence of metamorphic rocks that don’t contain amphiboles. Locality NE of Vareš near the village of Vijaka is generally the best outcrop of amphibolite rocks. The results of petrologic studies indicate that the analyzed rocks can be divided into several groups like garnet-diopside amphibolite, garnet-diopside-hypersthene amphibolite, plagioclase-garnet rocks, garnet-pyroxene-plagioclase schist; plagioclase-garnet-hornblende - diopside schist and porphyryblastic hornblende and garnet bearing schist. The garnets show wide variation in chemical composition with prevalance of almandine and pyrope component in all of analyzed samples. The differences in the composition profile through the garnets are attributed to changes in the metamorphic conditions during the growth of minerals. Abrupt changes in distribution of elements were observed in a thin zone on the very edge of the garnet grains which is interpreted as a result of the retrograde phase of metamorphism and rapid cooling.

Formulation of cost function for constructing a new transportation route

Asma Th. Ibraheem and Abeer Jabbar Abd- Al Razaq

A principal objective of transportation route design is to minimize the total cost including all significant components. The cost functions for a highway, which is developed in this thesis, have been incorporated into programmed software named Transportation Route Cost Analysis (TRCA) written using VBASIC Language. These functions reflect the costs due to different cost function characteristics such as Administrative Cost, Construction Cost, Maintenance Cost, User Costs, which include: (Tire Cost, Oil Cost, Fuel Cost, Travel Time Cost and Accident Cost) and finally Social and Environmental Costs, while most existing models in Iraq only considered Construction Cost, or even just one component such as earthwork cost. A case study is also presented to evaluate the modeled software of a highway having a length (12.644) km including a bridge crossing Tigris River of length (420) m with three intersections. According to the State Corporation for Roads and Bridges (SCRB), the gross domestic product is about (60,000,000,000) ID. This value is greater than the value obtained by the software (TRCA) because of the elimination of Accident Cost since no information regarding this type of cost is available in (TRCA), also, the duration of each cost considered in this program is only one year.

Investigation of airfoil profile design using reverse engineering Bezier curve

J. Fazil and V. Jayakumar

Abstract:

Though it is easier to model and create an airfoil profile in CAD environment using camber cloud of points, after the creation of vane profile it is very difficult to change the shape of profile for analysis or optimization purpose by using cloud of points. In this paper, we investigate and describe the creation of airfoil profile in CAD (CATIA) environment using the control point of the camber profile. By means of changing the values of control points the shape of the profile can be easily changed and also the design of the cambered airfoil is established without affecting the basic airfoil geometry. In this paper, the Quintic Reverse Engineering of Bezier curve formula is used to find the camber control points from the existing camber cloud of points.

A new method to incorporate TCSC in optimal power flow using genetic algorithm

Satyendra Singh and K. S. Verma

Abstract:

In this work, Genetic Algorithm (GA) for the solution of the optimal power flow (OPF) with use of Thyristor Controlled Series Compensator (TCSC) is studied. The specified power flow constraints due to use of TCSC are included in the OPF in addition to the normal conventional constraints. The sensitivity analysis is carried out for the location of TCSC. This method provides an enhanced economic solution. Traditionally, classical optimization methods were used to effectively solve OPF. But more recently due to incorporation of Flexible A.C. Transmission System (FACTS) devices and deregulation of a power sector, the traditional concepts and practices of power systems are superimposed by an economic market management. So OPF have become complex. In recent years, Artificial Intelligence methods (GA etc) have emerged which can solve highly complex OPF problems. 5-bus system has been studied to show the effectiveness of the algorithm.

Nonlinear damped oscillations- A case study of dysfunctions in smooth pursuit eye tracking-II

C. V. Pavankumar and N. Ch. Pattabhi Ramacharyulu

This paper presents a simple deterministic model of dysfunctions of eye- tracking. The model is formulated as a second order nonlinear ordinary differential equation, incorporating non Hookesien cubic restoring force. The equation is solved by employing a perturbation technique with the nonlinear restoring force coefficient as the perturbation parameter. Numerical estimation of the angular velocity is computed for a wide spectrum of the eye dysfunction. The significance of the effects of time, the frequency and amplitude of the exiting force on displacement has been discussed by adopting ANOVA technique. The critical levels of time and frequency have also been noted to be 2.761sec and 0.181149375, respectively corresponding to the 0.05 level of significance.

Strength and water penetrability of fly ash geopolymer concrete

Monita Olivia and Hamid R Nikraz

Abstract:

This paper presents a study on the strength development, water absorption and water permeability of low calcium fly ash geopolymer concrete. Geopolymer mixtures with variations of water/binder ratio, aggregate/binder ratio, aggregate grading, and alkaline/fly ash ratio were investigated. OPC (Ordinary Portland Cement) concrete with the same strength level was used as a control mix. Strength was measured by compressive strength, while water penetrability was evaluated by water absorption and water permeability. In addition, the AVPV (Apparent Volume of Permeable Voids) was measured. The results show that the strength of fly ash geopolymer concrete was increased by reducing the water/binder and aggregate/binder ratios; and the water absorption of low calcium fly ash geopolymer was improved by decreasing the water/binder ratio, increasing the fly ash content, and using a well-graded aggregate. There was no significant change in water permeability coefficient for the geopolymer with different parameters. The test data indicates that a good quality of low calcium fly ash geopolymer concrete can be produced with appropriate parameterisation and mix design.

Possibilities of GA in optimization of manufacturing cell formation

V. Modrák, S. Pandian and P. Knuth

Abstract:

Optimization of manufacturing cell formation includes a whole virtual cell formation procedure and has NP-hard complexity. In the last decades, evolutionary algorithms have been widely applied to real-world optimization including to manufacturing cell formation problems. Genetic algorithms (GAs) are possibly the most widespread variant of evolutionary algorithms and are now frequently used for a number of optimization problems in operation management.  In this study it is discussed about theoretical and practical aspects of GA to bridge the gap between hypothetical analysis and real time implementation of GA in a given domain.

A study on the engineering behaviour of Nairobi subsoil

Caroline Onyancha, Eliud Mathu, Sixtas Mwea and Wilson Ngecu

Abstract:

Nairobi city is underlain by volcanic materials that resulted from the formation of the rift valley. Some of the challenges that face design of structures in the city include the following:  need to develop structures even in areas with poor site conditions; distress in structures that could be related to foundation conditions; encounter of unexpected subsoil conditions even after carrying out some geotechnical investigations, and; development of defects related to adjacent deep excavation. The objectives of this study were: investigate the qualitative and quantitative properties of subsurface materials, to establish the engineering property variations and to provide properties that represent the best estimates. Information available for this study included Atterberg limits, grading, consolidation, swell and collapse, triaxial shear and direct shear, point load and unconfined compressive strength. Failure investigation and resistivity survey were carried out to fill in the gaps in the available information. The results indicate that the engineering properties of the materials are very variable. Material property variations and the expected performance of the various subsoil materials are provided. The study concluded that before construction, it is necessary to carry out geotechnical investigations to delineate sensitive soils, determine weak and strong spots and evaluate the relationship between total and differential settlements.

High quality rectifiers with reduced THD for enhanced mains power quality - Vienna with synchronous logic

Anantha Baddam Reddy and G. Tulasi Ram Das

Abstract:

A synchronous logic control based three-phase boost unity power factor rectifier unit that works as an interface to ensure high energy efficiency by reducing reactive power consumption, as well as to maintain a constant DC-bus voltage. This paper discusses the determination of performance characteristics of Vienna rectifier topology with the synchronous logic based control. Furthermore this enabled the design and development of a three-phase active converter system that was built and tested with the inputs and output. This paper also describes the Vienna Rectifier’s power stage and synchronous logic control technique, with particular emphasis on finding differences between real prototype results and the simulation results. The design and experimental performance of a three-phase PWM rectifier with a power output of 3 kW is presented. The real prototype results confirm with the simulation results.

Experimental study for heat and mass transfer from moist air flowing over moving water film

Ahmed F. Khudheyer

Abstract:

Heat and mass transfer from or to a horizontal moving water film to airflow flowing over the film inside a rectangular duct wind tunnel is investigated, experimentally. To perform the experimental study for this phenomenon air flows inside a rectangular duct over a moving water film flow inside the duct, which is fixed in the floor of the tunnel. Therefore, some of the water film is evaporated from the water surface to the air flowing over it. The following measurements for velocity of moist air and water, temperature, humidity, are taken at five positions along test section and upstream of the water panel with a range of Reynolds number of (1000-30000). Also, the amount of water evaporated through each experiment is measured. The results show that, Nusselt and Sherwood numbers increase with increasing Reynolds number. Comparison between the obtained results and the previous works show good agreement.

Effect of slip on heat transfer to peristaltic transport in the presence of magnetic field with wall effects

A. V. Ramana Kumari and G. Radhakrishnamacharya

Abstract:

The effects of slip and elasticity of flexible walls on peristaltic transport of an incompressible viscous fluid in a two dimensional uniform channel, with heat transfer in the presence of magnetic field is investigated. Using long wavelength approximation, a perturbation solution has been obtained in terms of wall slope parameter and closed form expressions are derived for average velocity, temperature and heat transfer. The effects of various pertinent parameters on average velocity and heat transfer coefficient have been studied. The time average velocity increase with slip but decrease with permeability. Trapping phenomenon is more significant for lower values of slip parameter, higher permeability and almost disappears for higher values of magnetic parameter. Further, the heat transfer coefficient increases with slip but decreases with permeability.

Seismic analysis of t shape rigid Bridge with high piers

Qingxiang Zheng and Wenhua Liu

Abstract:

Combined with seismic resistance of T shape rigid bridge with high piers in Dina 2 gas-field of China, comparative analysis on double thin-wall piers and hollow thin wall pillar is carried out. Focusing on seismic performance of their dynamic properties and structure under the condition of one-way incentive and three-dimensional space incentive, we conclude that the seismic performance of double thin-wall piers is superior to hollow thin wall pillar, on the basis of the fact that double thin-wall piers contains more than hollow thin wall pillar low-frequency vibration frequency in sectional characteristic and pier under the condition of high basic agreement, which is easily causing to frequency dispersion.