IMECE2005-80469 A COMPARATIVE STUDY OF CROSS-FLOW INDUCED VIBRATIONS IN HEAT EXCHANGER TUBE BUNDLES USING BOND GRAPH APPROACH

ABSTRACT Flow-induced vibration (FIV) has been a major concern in the nuclear and process industries involving steam generator and heat exchanger tube bundle design. Various techniques and models have been developed and used for the analysis of crossflow induced vibration of tube bundles. Bond Graph approach has been applied to existing FIV excitation models, followed by a comparative study. Results have been obtained using 20-SIM software. It is expected that the current approach will give a new dimension to the FIV analysis of tube bundles

Efficiency of Virgin's Mantle (Fagonia cretica L.) as an Antibacterial and Antifungal Agent

Background: For medicinal purposes, biological activities are carried out on plant secondary metabolites in which common but very significant antimicrobial activities are focused. To evaluate the antimicrobial potential of Fagonia cretica L., different pathogenic microbial strains were obtained from KP, hospitals (already identified) to resolve the objectives of the current study.Methods: In the agar, well diffusion method, a total of eight strains (4 bacterial 4 fungal) Streptococcus mutans, MRSA (Methicillin resistance staphylococcus aureus), Serratia marcescens, and Staphylococcus aureus are the bacterial strains while the fungal strains are Alternaria alternate,  Aspergillus flavus, Fusarium oxysporum, and Polysphondylium pallidum pre-identified and isolated in hospitals, were used respectively to evaluate the potentiality of n-hexane, ethyl acetate, chloroform, aqueous, and crude methanolic fractions against these strains.Keywords: Virgin’s mantle; Fagonia cretica; Antibacterial; AntifungalResults: The highest significant (46-57% & 39-60%) antibacterial and antifungal activities were shown by the methanolic fraction while the lowest (28-35% & 25-35%) antibacterial and antifungal was shown by aqueous fraction against the selected microbial strains. Other fractions were also exhibited reasonable antimicrobial activities.Conclusion: The current study concluded that different fractions of F. cretica have significant antimicrobial potential and might be a source of antibiotics in future studies of that plant.Keywords: Virgin’s mantle; Fagonia cretica; Antibacterial; Antifungal

Competence of Benzoil Tree (Moringa Oleifera L.) as Antibacterial and Antifungal Agent

Background: A plant’s activity towards biological properties is the first step to consider it for medicinal and therapeutic purposes. To evaluate the medicinal properties, we have determined the anti-bacterial and anti-fungal potential of Moringa oleifera L. (Benzoil tree). The focus was to obtain and isolate certain chemical substances that can neutralize the effect of common and pathogenic selected bacterial and fungal species collected from local hospitals of Khyber Pakhtunkhwa.Methods: A total of five fractions were selected i.e. crude methanolic extracts, n-hexane, chloroform, ethyl acetate and aqueous extracts were prepared and their activity checked against four bacterial strains including Streptococcus mutans, Staphylococcus aurous, MRSA (methicillin resistance Staphylococcus aurous) and Serratia marcescens; and four fungal strains i.e. Fusarium oxysporum, Aspergillus flavus, Polysphondylium pallidum and Alternaria alternata.Results: The highest anti-bacterial activity shown by crude methanolic extract fraction i.e. (48-38%) and the lowest activity was exhibited by aqueous extract (15-0%) against all the selected bacterial strains. Similarly, the highest anti-fungal activity indicated by crude methanolic extracts (60-45%) against the four selected fungal species and lowest activity shown by the aqueous fractions (26-0%). Reasonable activity was also exhibited by others fractions as well.Conclusion: The outcomes of our experiment strongly supports that Moringa oleifera has significant antibacterial and antifungal activities, so the plant is effective antibacterial and antifungal agent.Keywords: Benzoil tree; Moringa oleifera; Antibacterial; Antifungal; Drum stick Tre

Experimental investigation of PCM based round pin-fin heat sinks for thermal management of electronics: effect of pin-fin diameter

This experimental study presents the parametric analysis for the round pin-finned heat sinks subjected to steady heat densities for effective and reliable cooling of mobile electronic devices. Phase change material (PCM) namely paraffin wax is adopted as energy storage material and aluminum made round pin-fins are selected as thermal conductivity enhancers (TCEs). A constant volume fraction of 9% of round pin-fins is selected with pin diameter of

Techniques for Thermal Damping in Tube Bundles

Flow-induced vibration in heat exchangers has been a source of concern in the process, power generation and nuclear industry for several decades. Damping has a major influence on the flow induced vibrations and is dependant on a variety of factors such as mechanical properties of the tube material, geometry of intermediate supports, the physical properties of shell-side fluid, type of tube motion, number of supports, tube frequency, shell-side temperature etc. Various damping mechanisms have been identified and quantified. Generally the effects of the higher operating temperatures on the various damping mechanisms are neglected in the general design procedure. This paper focuses on the thermal aspects of damping mechanisms subjected to single phase cross-flow in shell and tube heat exchanger and a comparison is carried out safer design based on experimental and empirical formulations

FEDSM2006-98397 DYNAMIC ANALYSIS OF FLUID FLOWING THROUGH MICRO POROUS FILTERS USING BONDGRAPH APPROACH

ABSTRACT Delivery of optimized fuel injection pressure to combustion chamber of an engine assembly leads to optimum torque and horsepower. Contaminant free supply of fuel without compromising on volume flow rate is the most important design requirement. Incorporation of very fine fuel filters having less than 10 micron rating reduces volume flow rate at the injection nozzles whereas fuel filter with larger pore size stabilize the injection pressure but may result into failure of fuel injection pump assembly due to scuffing produced by the fuel contaminant between the plunger and sleeve of hydraulic head of fuel injection pump. The fuel flows from fuel tank through low-pressure injection line, primary and secondary fuel filters, fuel transfer pump, fuel injectioin pump, and high-pressure injection line and injector nozzles. Modeling and simulation of volume flow rate vis-à-vis fuel injection pressure together with micro-porous fuel filter poses a formidable challenge. Bondgraph method (BGM) is ideally suited for the modeling and simulation of such a multi-domain dynamic system. The aim of this research is to apply BGM to model and simulate the optimized fuel injection pressure and analysis of filters with different micro-porosity and their effect on volume flow rate. Fuel filter porosity, inlet and outlet pressures of transfer pump, fuel injection pump and low/high pressure injection line pressure have been determined experimentally. These experimentally determined parameters are then used as input in our Bondgraph model for the dynamic analysis of fuel injection pressure incorporating micro-porous filters

Fretting Wear Analysis of Different Tube Materials Used in Heat Exchanger Tube Bundle

Research on heat exchange is being carried out for more than five decades because of its importance in process industries and power generation plants. Heat exchanger experiencing cross flow are vulnerable to flow induced vibration. These vibration causes the interaction of tubes with the baffle resulting in a fretting wear of the tubes. Present study focuses on the fretting wear analysis of different tube materials. Fretting wear tests were performed on aluminum, copper and stainless steel instrumented central tubes against mild steel baffle. For each tube material the tests were performed for three different test durations i.e. 60 minutes, 120 minutes and 180 minutes at a cross flow velocity of 0.55 m/s. It was observed that vibrational amplitude of the flexible test tube is affected by its weight. A scanning electron microscope was used to analyze and measure the sizes of wear scar. The results indicated that wear loss in case of aluminum tube is the highest while that in case of stainless steel tube is the lowest

Prediction of non-propagating fretting fatigue cracks in Ti6Al4V sheet tested under pin-in-dovetail configuration: Experimentation and numerical simulation

International audienceThis paper presents the results of fretting fatigue tests carried out on Ti6Al4V sheet specimens in contact with carbide rod in a cylinder-on-flat contact configuration. A new methodology of carrying out fretting fatigue experiments is proposed and successfully implemented using a pin-in-dovetail and pin-in-hole configuration. The advantage of this configuration is the simplicity and ease of application. The tests are carried out on MTS 810 at different loads, constant frequency (30 Hz) and ambient conditions. These tests reveal that the crack initiation and propagation are dependent on the applied load and the configuration of the contact. At low loads, non-propagating cracks are observed in the pin-in-dovetail configuration using metallurgical microscope. At high loads these cracks become longer but are still non-propagating. Numerical simulation using elastic plastic material model is carried out to determine stress intensity factor and the mode of crack propagation. Maximum principal stress damage criteria approach is used to predict the crack initiation sites under different loads and a strong correlation with experimental results is observed. The crack propagation is simulated using XFEM, which successfully simulates the non-propagating crack length. (C) 2015 Elsevier Ltd. All rights reserved