Showing papers in "Volume! in 2004"

State of the Art in Laser Surface Texturing

Abstract: Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components. Various techniques can be employed for surface texturing but Laser Surface Texturing (LST) is probably the most advanced so far. LST produces a very large number of micro-dimples on the surface and each of these micro- dimples can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a micro-reservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for wear debris in either lubricated or dry sliding. The paper reviews the current effort being made world wide on laser surface texturing in particular. It presents the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings, thrust bearings, magnetic recording etc. The paper also describes some fundamental on-going research around the world with LST.

Computations of Boiling Flows

Abstract: Numerical simulations of boiling flows are discussed. The change of phase from liquid to vapor and vice-versa usually takes place in a highly unsteady manner where the phase boundary is very convoluted. Direct numerical simulations therefore require the accurate solution of the Navier-Stokes equations and the energy equation in each phase and the correct incorporation of the unsteady phase boundary. Such simulations, where the motion of an unsteady phase boundary is followed for a sufficiently long time to allow computation of average heat transfer are very recent. Here, we will describe one method that has been used successfully to simulate boiling flows and show a few examples of studies using the method.Copyright © 2004 by ASME

A Survey on Condition Monitoring Systems in Industry

Abstract: Advances in networking technologies are opening integration opportunities for Condition Based Monitoring (CBM) systems, presenting further possibilities for increasing CBM system functionality. This paper presents the results of a CBM Survey designed to determine present applications of CBM system within industry. Understanding how industry applies practices such as CBM in the work place offers valuable research results for CBM system providers, consultants and business users alike. The survey acts as a CBM application indicator for 2004. It targets 6 key areas: 1) Respondents’ company information, 2) The type of CBM technique/s applied by the respondents’ company, 3) Incentives that led the respondents’ company to implement their CBM system, 4) Technological and integration issues associated with respondents’ application of CBM, 5) Implementation issues associated with the respondents’ CBM system, and 6) Reliability and consequential maintenance awareness issues following implementation. An international response shows CBM to be a globally accepted maintenance practice. In addition to the survey results, the paper discusses developments in remote CBM systems using the Internet, with particular regard for developing suitable user interface designs.Copyright © 2004 by ASME

Odyssey of the Enhanced Boiling Surface

Abstract: This paper traces the evolution of enhanced boiling surfaces. Early work was highly empirical and done in industrial research. The 1968 Milton patent described the first porous coated surface, and the 1971 Webb patent described a “structured” tube surface geometry. The first fundamental understanding of the “pore-and-tunnel” geometry was published by Nakayama in 1980. Webb and Chien’s flow visualization allowed observation of the evaporation in the sub-surface tunnels. They also performed an experimental parametric study that defines the effect of pore diameter and pitch on the boiling performance. The progression of work on analytical boiling models is also reviewed.Copyright © 2004 by ASME

Film Boiling Heat Transfer on a High Temperature Sphere in Nanofluid

Abstract: Quenching experiments of a high temperature sphere in Al2 O3 nanofluids are conducted to investigate the characteristics of film boiling and compared to those in pure water tests. One stainless steel sphere of 10 mm in diameter at the initial temperatures of 1000∼1400 K was tested in the nanofluids of the volume concentrations from 5 to 20% and the degrees of subcooling from 20 to 80 K. The test results show that film boiling heat fluxes and heat transfer rates in nanofluids were lower than those in pure water. The differences of the film boiling heat transfer rates between pure water and nanofluids become larger when the liquid subcooling decreases. Those results suggest that the presence of nanoparticles in liquid enhances vaporization process during the film boiling. The effects of nanoparticle concentrations of more than 5 vol. % on film boiling appear to be insignificant. However, the minimum heat fluxes tend to decrease when the concentration increases. Direct quenching without film boiling was repeatedly observed when an unwashed sphere was employed for quenching tests in nanofluids. It suggests that nanoparticle deposition on the sphere surface prevents the sphere from forming film around the sphere, which consequently promotes the rapid quenching of the hot sphere.Copyright © 2004 by ASME

Deux exemples de presse musicale jeune en France, de 1966 à 1969 : Salut Les Copains et Rock & Folk

Abstract: a l’heure ou la mode hippie explose en France, en 1966, s’affrontent dans la presse musicale dediee aux jeunes deux points de vue opposes. D’un cote, la legitimite historique de Salut Les Copains, journal cree en 1962 par deux anciens de l’emission d’Europe 1 « Pour ceux qui aiment le jazz », Daniel Filipacchi et Frank Tenot. De l’autre, Rock & Folk cree en 1966 par des jeunes journalistes autant engages politiquement que musicalement, vers les nouveautes anglo-saxonnes.Le premier s’evertue a encadrer les revendications, et les explosions artistiques d’une classe d’âge qui est maintenant totalement soumise a un marketing cree pour elle. Salut Les Copains ne cherche que le cote federateur d’une musique rock qui commence a devenir encombrante par son refus d’etre un pur divertissement. Le second est un journal cree par des jeunes, un espace enfin ouvert de communication entre membres d’une meme tranche d’âge, qui ont les memes references culturelles et les memes besoins de sortir des carcans imposes par les adultes.

Micro Fluidic Jets for Thermal Management of Electronics

Abstract: Micro fluidics devices are conventionally used for boundary layer control in many aerospace applications. Synthetic Jets are intense small scale turbulent jets formed from entrainment and expulsion of the fluid in which they are embedded. The idea of using synthetic jets in confined electronic cooling applications started in late 1990s. These micro fluidic devices offer very efficient, high magnitude direct air-cooling on the heated surface. A proprietary synthetic jet designed in General Electric Company was able to provide a maximum air velocity of 90 m/s from a 1.2 mm hydraulic diameter rectangular orifice. An experimental study for determining the thermal performance of a meso scale synthetic jet was carried out. The synthetic jets are driven by a time harmonic signal. During the experiments, the operating frequency for jets was set between 3 and 4.5 kHz. The resonance frequency for a particular jet was determined through the effect on the exit velocity magnitude. An infrared thermal imaging technique was used to acquire fine scale temperature measurements. A square heater with a surface area of 156 mm2 was used to mimic the hot component and extensive temperature maps were obtained. The parameters varied during the experiments were jet location, driving jet voltage, driving jet frequency and heater power. The output parameters were point wise temperatures (pixel size = 30 μm), and heat transfer enhancement over natural convection. A maximum of approximately 8 times enhancement over natural convection heat transfer was measured. The maximum coefficient of cooling performance obtained was approximately 6.6 due to the low power consumption of the synthetic jets.Copyright © 2004 by ASME

Experimental investigation of the flow field of a ceiling FAN

Abstract: A ceiling fan is the predominating comfort provider in tropical regions worldwide. It consists of an assembly of an electric motor with 3–4 blades suspended from the ceiling of a room. Despite its simplicity and widespread use, the flow induced by a ceiling fan in a closed room has not been investigated, and sub-optimal designs are in wide use. There is vast potential for energy conservation and improved comfort by developing optimized fan designs. This work develops a fundamental understanding of the flow characteristics of a ceiling operating inside a closed room. Using smoke from thick incense sticks, the flow field created by the ceiling fan is visualized. In most regions, the flow is periodic and three-dimensional. Vortices are seen to be attached to the blade tip and hub, which reduces downward flow and increases energy consumption. Only the middle 75% of blade actually pushes the air downwards, and the comfort region is limited to a cylinder directly under the blades; velocities in this region were measured with a vane anemometer. Winglets and spikes attached to the blade tip disrupted the tip vortex, and increased downflow by about 13% without any increase in power consumption.Copyright © 2004 by ASME

Combined Deterministic-Stochastic Frequency-Domain Subspace Identification for Experimental and Operational Modal Analysis

Abstract: Until recently frequency-domain subspace algorithms were limited to identify deterministic models from input/output measurements. In this paper, a combined deterministic-stochastic frequency-domain subspace algorithm is presented to estimate models from input/output spectra, frequency response functions or power spectra for application as experimental and operational modal analysis. The relation with time-domain subspace identification is elaborated. It is shown by both simulations and real-life test examples that the presented method outperforms traditional frequency-domain subspace methods.Copyright © 2004 by ASME

Design for Patient Safety: A Review of the Effectiveness of Design in the UK Health Service

Abstract: The health service is a highly pressured complex system where the potential for error and accidents is ever present. Ensuring the safety of people who come into contact with health services is one of the most important challenges facing healthcare today, not just in the UK but worldwide. Medical error in hospitals is now believed to be the seventh most common cause of death in America [Kohn et al. 1999] and perhaps as much as a half of these adverse events are judged to be avoidable. In the UK, it has been estimated that 850,000 medical errors occur every year – equating to some 10% of hospital admissions, the cost of which is suffering for patients, families and NHS staff involved and £2billion in additional hospital stays alone [Yeates et al. 2001]. Design is a structured process for identifying problems and developing, testing and evaluating user focussed solutions. It has been successfully used to transform products, services systems and even entire organisations. When applied to healthcare, effective design thinking can deliver products, services, processes and environments that are intuitive, simple to understand, simple to use, convenient, comfortable and consequently less likely to lead to accidental misuse, error and accidents. By contrast, confusing, complex and unwieldy designs – which are all too often present in healthcare are at best less effective than they could be, at worst they are potentially dangerous to either medical staff or the patient or both [Bates et al. 1997]. The remainder of this paper describes a study commissioned by the Department of Health, in conjunction with the Design Council, the lessons learned and the key findings presented.

Gas Turbine Power Augmentation Using Fog Inlet Air-Cooling System

Abstract: Gas turbines are almost constant volume machines at a specific rotating speed, i.e., air intake is limited to a nearly fixed volume of air regardless of ambient air conditions. As air temperature rises, its density falls. Thus, although the volumetric flow rate remains constant, the mass flow rate is reduced as air temperature rises. Power output is also reduced as air temperature rises because power output is proportional to mass flow rate. This power output reduction is from 0.5% to 0.9% of the ISO output power for every 1°C rise in the ambient temperature. The solution of this problem is very important because the peak demand season also happens in the summer. One of the useful methods to overcome this problem is to apply the fog inlet air cooling system for the gas turbines. In this paper the Rey Power Plant site climate conditions in the summer have been studied. The design conditions regarding the dry bulb temperature and relative humidity have been selected. The different inlet air cooling systems have been studied and the Fog system has been chosen. The economical study has shown that this system is very cheap in comparison with the installation of the new gas turbines. The capital cost is estimated to be 40 $/KW. The pay back period is around 1.5 year. The testing of this system has shown that the average power capacity of the power plant is increased by 19 MW and prevented the installation of a new gas turbine.Copyright © 2004 by ASME

Effect of Spray Angle in Spray Cooling Thermal Management of Electronics

Abstract: The paper presents an experimental and numerical study of the effect of spray angle on spray cooling when applied in the thermal management of electronics. A thermal test chip provided the heated target, and was cooled by a single pressure swirl atomizer. A perfluorocarbon (PF5060) was employed as the coolant. The coolant was subcooled to a fixed level of 26° C, and was sprayed directly onto the heated target at a fixed flow rate of 22 ml/min. The spray angle was varied between 0 and 60 degrees, and the outlet of the atomizer was located at a fixed radius of 1.4 cm from the heated target. The model of Mudawar and Estes (1996) was also modified to account for the effect of spray angle, then used to assist in interpretation of the experimental data. In an effort to estimate the heat transfer characteristics, an inverse heat transfer algorithm is developed. A direct finite element model is applied with estimated heat flux distributions to simulate the thermal field in the test microchip for various cooling conditions. Experimental results are presented for a number of cases and compared with the model’s predictions. The experimental data and model both showed that cooling capability dropped off when spray angle exceeded 50 degrees.Copyright © 2004 by ASME

Heat Exchanger Design for the Process Industries

Abstract: The design process for heat exchangers in the process industries and for similar applications in the power and large-scale environmental control industries is described. Because of the variety of substances (frequently multicomponent, of variable and uncertain composition, and changing phase) to be processed under wide ranges of temperatures, pressures, flow rates, chemical compatibility, and fouling propensity, these exchangers are almost always custom-designed and constructed. Many different exchanger configurations are commercially available to meet special conditions, with design procedures of varying degrees of reliability. A general design logic can be applied, with detailed procedures specific to the type of exchanger. The basis of the design process is first a careful and comprehensive specification of the range of conditions to be satisfied, and second, organized use of a fundamentally valid and extrapolatable rating method. The emphasis in choosing a design method is upon rational representation of the physical processes, rather than upon high accuracy. Finally, the resultant design must be vetted in detail by the designer and the process engineer for operability, flexibility, maintainability, and safety.Copyright © 2004 by ASME

Microscale Ion-Driven Air Flow Over a Flat Plate

Abstract: A microscale air pump concept that uses ionized air molecules under the influence of an electric field is studied. The method employed is an extension of the corona wind concept and is referred to here as microscale ion-driven air flow. The two major differences are that the ions are created in a distinct generation region, and are then put in motion by a traveling electric field in the pumping region. The ions create bulk motion of the air because of ion drag. One application of this technology involves generation of air flow through microchannels or other micro-featured surfaces to create compact, high flux heat sinks for electronics cooling. This work focuses on the ion pumping aspect of the technology. A device was constructed and tested with an array of micro-fabricated electrodes that generate strong electric fields in the air. The electrode potentials were cycled to impart a unidirectional force to the ions over meso-scale distances. The microscale ion-driven air flow concept was demonstrated by electrical means, through the measurement of the ion current produced. A set of designed experiments were conducted that showed the electrode potential to be the most significant factor for sustaining an ion current. A two-dimensional numerical model of the ion motion has been developed and validated against the experimental results. The model describes the time-dependent ion flow induced over an array of evenly spaced microscale electrodes that are used to generate a translating electric field.Copyright © 2004 by ASME

Analytical Study of Natural Convection in a Cavity With Volumetric Heat Generation

Abstract: A semi-analytical method for natural convection in a two dimensional rectangular enclosure, with uniform volumetric heat generation, having insulated horizontal boundaries, and isothermal vertical boundaries, has been studied here. In this method, the governing equations for natural convection, have been solved under the assumption that for a cavity with small aspect ratio, the flow in the central region of the cavity is only in the vertical direction. It is found that for the cavities with small aspect ratio, the temperature in central region of the cavity is nearly constant along the horizontal direction. However, there is a uniform temperature gradient in the vertical direction, which can be related to the maximum temperature in conduction. The velocity profiles and temperature profiles obtained in the present work, are compared with the numerical simulations by Fluent and a fair agreement is found between these results.Copyright © 2004 by ASME

Visualisation of two-phase gas-liquid pipe flows using electrical capacitance tomography

Abstract: Electrical Capacitance Tomography (ECT) has been used over a number of years to measure concentration distribution, and more recently velocity distribution, in two-phase flows ECT is non-intrusive, and the reconstruction of the concentration and velocity distribution can be undertaken in real time and over an arbitrary number of zones in the flow cross-section In this paper the concept of a ‘virtual instrument’ is introduced where zones of the image can be structured for comparison with other measurements Numerical agreement with gamma-ray density measurements is shown to be excellent in slug and stratified flows We present a series of measurements undertaken in complex oil/gas slug flows in a large flow loop We present a variety of 2-D cross-sectional images, time series velocity and concentration graphs and 3-D contour plots The good temporal and spatial resolution of ECT throws an extensive new light on these otherwise difficult to measure dynamic flow structures In particular with bubbly-slug structures known as ‘ghosts’ ECT shows clearly that they are in fact bubbly waves which have extended ‘wings’ up and around the pipeCopyright © 2004 by ASME

An industrial robot and a laser scanner as a flexible solution towards an automatic system for reverse engineering of unknown objects

Abstract: Reverse Engineering(RE) is concerned with the problem of creating CAD-models of real objects by measuring point data from their surfaces. Current solutions either require manual interaction or expe ...

Cavitation detection of a centrifugal pump using instantaneous angular speed

Abstract: Cavitation is a common fault in centrifugal pumps. The detection and diagnosis of the onset and severity of the cavitation provide the means of preventing the cavitation from causing harmful effects such as deterioration of the hydraulic performance, damage to pump components and the pollution by vibration and noise. This paper presents a new approach to monitoring cavitation based on the measurement of instantaneous angular speed (IAS) of the pump. IAS is measured using a cheap shaft encoder and processed using order spectrum analysis. It has been found that the normalised amplitude at the third order of the rotational speed can be used as a primary monitoring feature to detect the onset of the cavitation and to quantify the severity of the cavitation. A secondary detection feature is also defined in the high frequency range. This makes the detection results more reliable.

A one-dimensional numerical model for calculating the efficiency of Pumps As Turbines for implementation in micro-hydro power plants

Abstract: Increasing interest in renewable energy sources makes attractive the exploitation of many small power hydraulic resources (micro-hydro – less than 100 kW). However, the high cost of hydraulic turbines hinders the actual realization of micro-hydro plants. An alternative cheaper solution could be to replace the turbine with a reverse-mode centrifugal pump, developing therefore a pump as turbine (PAT) system. Unfortunately, although a wide number of centrifugal pumps are commercially available for micro-hydro engineering plant, manufacturers do not provide information regarding the performance of centrifugal pumps in turbine mode. In this paper, a simple method based on a one-dimensional numerical code is presented for deriving the turbine efficiency of commercially available centrifugal pumps. The code estimates a sizing of the component using information such as impeller diameter, specific speed, head and flow rate at pump BEP, machine overall dimension which are provided in manufacturer catalogues, to deduce geometrical parameters of the machine, calculating the losses and thus determining PAT performances. The method was validated by a comparison of the predicted characteristic curves with some experimental measurements available on PATs working in a range of specific speed (Head in meters and flow rate in m3 /s) from 9 to 65. The numerical code calculations effectively predicted the measured efficiency of PATs. At BEP, the efficiency was estimated with a relative error of ±10% which is a value much lower than one obtained by using the available in literature correlations. A prediction within this error range is generally accepted for this kind of application.Copyright © 2004 by ASME

Mathematical Model and Surface Deviation of Cylindrical Gears With Curvilinear Shaped Teeth Cut by a Hob Cutter

Abstract: The generating motion of a cylindrical gear with curvilinear shaped teeth cut by a CNC hobbing machine is proposed. Based on the cutting mechanism and the gear theory, the surface equation of this kind of gear is developed as a function of hob cutter design parameters. Computer graphs of the curvilinear-tooth gear are presented based on the developed gear mathematical model, and the tooth surface deviations due to machine-tool setting with nominal radius of circular tooth trace are also investigated.Copyright © 2004 by ASME

Exhaust-Gas Reforming of Methane to Aid Natural Gas HCCI Combustion: Experimental Results of Open Loop Hydrogen Production and Basic Thermodynamic Analysis

Abstract: The Homogeneous Charge Compression Ignition (HCCI) combustion has potential to radically reduce emissions, especially NOx, but is inherently difficult to achieve and control, especially when natural gas is used as fuel. Hydrogen addition, particularly from fuel reforming was successfully used as an aid. Methane reforming with exhaust gas and air in a monolith catalytic reactor is presented here as a source of hydrogen. An open-loop fuel exhaust gas reforming system has been developed and tested; experimental results are compared with two different models of basic thermodynamic equilibria calculations. The experimental results have shown that for low temperature of engine exhaust gas, typical for HCCI conditions, additional air is needed to produce the quantities of H2 required to enhance the feasibility and range of HCCI combustion. At the low reactor inlet temperatures needed for the HCCI application the simplified three-reaction thermodynamic model is in broad agreement with experimental results, while the high hydrogen yields predicted from the multi-component equilibrium model for medium temperature reforming are difficult to achieve in a practical reformer.Copyright © 2004 by ASME

Multiple Frequency Analysis Methods for Blade Tip-Timing Data Analysis

Abstract: Blade Tip-Timing (BTT) is a method for the measurement of blade vibration in rotating bladed assemblies such as those found in turbomachinery. The system aims to replace strain gauge technology. However all current BTT analysis methods fail to recover the correct frequencies when two blade modes are excited simultaneously by a synchronous vibration. In this paper, five new methods that can recover simultaneous frequencies from BTT data are presented. The methods are based on the auto-regressive approach. The approached make use of data either from a single blade and single revolution or from multiple revolutions. Furthermore, some of the methods are designed to allow for the presence of measurement errors. The techniques are validated on three test cases in which simulated data was used. It is shown that most of the methods produce accurate estimates for the vibration frequency, even in the presence of significant noise levels, provided that a suitable amount of the response waveform is measured. The most consistent estimates are obtained from the methods that make use of data from multiple revolutions.Copyright © 2004 by ASME

Cross-Sectional Imaging of the Liquid Film in Horizontal Two-Phase Annular Flow

Abstract: Planar laser induced fluorescence (PLIF) was applied to horizontal air/water two-phase annular flow in order to clearly image the liquid film and interfacial wave behavior at the top, side and bottom of the tube. The visualization section was fabricated from FEP, which has nearly the same refractive index as water at room temperature. This index-matched test section was used to allow imaging of the water to within approximately 10 microns of the 15.1 mm I.D. tube wall. A small amount of dye was added to the water with a peak excitation wavelength near that of a pulsed Nd:YAG laser (532 nm). The laser system generated an approximately 5 ns pulsed light sheet at 30 Hz. Images of the liquid film were captured using a digital video camera with a macro lens for a resolution of about 8.2 microns/pixel. Cross-sectional data at 68 annular flow conditions were obtained. The observations of the liquid film between waves indicated that the film thickness was relatively insensitive to both gas and liquid flow in the annular regime, confirming film thickness measurements reported elsewhere. In addition, the structure of waves changes significantly from wavy-annular, where peaked or cresting waves dominate, to fully annular, where the waves are much more turbulent and unstructured. The wave height decreases with increased gas flow and is relatively insensitive to increased liquid flow in the annular regime. The entrainment of gas in the liquid by the waves is very apparent from these images. Although the precise entrainment mechanisms are not entirely clear, a viable folding action mechanism is proposed. The visualization results will be discussed in relation to both conceptual and computational annular flow modeling.© 2004 ASME

High heat flux cooling with water jet impingement

Abstract: Accelerator targets, both for radioisotope production and for neutron sources generate thermal energy at very high density due to the absorption of the particles beam in the target material. Total power is in the order of 10–50 kW. Average heat fluxes are about 1 kW/cm2 and maximum values can exceed 5 kW/cm2 . The design of these targets requires efficient heat removal techniques in order to preserve the integrity of the target. Experimental cooling loops based on water and liquid gallium jet impingement have been designed in order to evaluate the actual potential of jet impingement for high heat flux cooling. The water cooling system is already operational and initial results have demonstrated a cooling capacity of 5 kW with average heat flux of 0.5 kW/cm2 and a maximum of about 1 kW/cm2 with a total target area of 10 cm2 . In order to test the system at higher power level we build an electron gun heat source that is designed to provide up to 20 kW heating power.Copyright © 2004 by ASME

Cryogenic Two-Phase Flow During Chilldown

Abstract: This work describes an experimental investigation of the transient two-phase flow behavior of liquid nitrogen flowing through a pipeline during the chilldown process. The evaporation process and flow regime transitions were observed during chilldown. Initially pure vapor is observed in the visual test section. Then a moving film boiling front is observed to move through the test section. The length of the film boiling front appears to be very small compared with the length of the facility pipeline. After the film boiling front passes through the test section, a very high velocity stratified two-phase flow appears with a small liquid film thickness. As the pipeline is chilled, the film thickness grows. It appears that the high velocity two-phase flow suppresses nucleate boiling, and the dominant heat transfer mechanism is two-phase bulk turbulent convection. Evaporation occurs at the liquid/vapor interface. A high-speed video camera is used to observe the flow regime transitions during the transient chilldown process. Flow regime comparisons have been made with the Steiner [1], Kattan-Thome-Favrat [2], and Baker [3] flow regime maps.© 2004 ASME

The Effect of Conjugate Heat Transfer on Film Cooling Effectiveness

Abstract: We investigate the numerical prediction of film cooling effectiveness of a two-dimensional gas turbine endwall for the cases of conjugate and adiabatic heat transfer models. Further, the consequence of various turbulence models employed in the computation are investigated by considering various turbulence models: ‘RNG’ k-e model, Realizable k-e model, Standard k-ω model, ‘SST’ k-ω model, and ‘RSM’ model. The computed flow field and surface temperature profiles along with the film effectiveness for one and two cooling slots at different injection angles and blowing ratio of one are presented. The results show the strong effect of the conjugate heat transfer on the film effectiveness compared to the adiabatic and analytically derived formulae and show that turbulence model used significantly affects the film effectiveness prediction when separation occurs in the film hole and some level of jet lift-off is present.Copyright © 2004 by ASME

Fault Diagnosis of a Centrifugal Pump by Vibration Analysis

Abstract: This paper gives the final Solution for vibration reduction in a centrifugal pump. Vibration measurement in different conditions has been carried out in order to find the main reason for excessive vibration of the pumps. In the first stage several parameters including cavitation, not working in the pump design condition and mechanical and electrical faults assumed to be the reason for the pump vibration. By vibration analysis it is found that the major reason for the pump vibration is working in off design conditions. More over dissolved air in the suction fluid can possibly cause two-phase flow leading to the pump vibration. For solving both problems considering pump performance curves it has been suggested to use a speed controller to reduce pump speed.Copyright © 2004 by ASME

A Review of the Condition Monitoring of Mechanical Seals

Abstract: Mechanical seals are the most widely used types of dynamic seal. Although its reliability has been improved by employing advanced technologies in design and manufacture in the last 40 years, premature failures of mechanical seals are still very common. The review of the failure of mechanical seal shows that the failure follows early and random distribution. Condition monitoring is then needed to predict the failures at their early stage to prevent additional loses. Possible methods for condition monitoring of mechanical seal are surveyed which include operation parameter monitoring, acoustic emission, ultrasonic wave, dynamic behaviour measurement, and air-born acoustic noise.Copyright © 2004 by ASME

Non-Intrusive Measurement of Volume and Mass Using Electrical Capacitance Tomography

Abstract: Electrical capacitance tomography (ECT) has been used for some years to measure the concentration distribution within multiphase flows and processes. ECT is a relatively low resolution measurement, but it has many advantages, including being non-intrusive and fast. Recent developments of twin-plane systems have enabled measurements to be made of velocity as well as concentration. We have developed techniques to establish from these measurements the volume, mass and velocity of flow structures in two-component flows, and in particular the mass and velocity of large individual particles and groups of particles in solids/gas flow systems. Results are presented in the paper for simple gravity-drop flows of partly-filled plastic spheres, plastic beads, and also for the conveying of granular material in a pilot plant. We show that resolution of mass to within a few grams is possible on objects of individual mass of between 2g and 35g. We also show measurements of flow structure volumes in vertical solids conveying pipes of approximately 50mm diameter. General comparisons are made with high-speed video photography of some of the flows, and the in the case of gravity-drop flows the accuracy of the mass measurement is established using weighing.Copyright © 2004 by ASME

Models and experiments for laminar natural convection from heated bodies in enclosures

Abstract: A combined experimental and analytical study of natural convection heat transfer in the enclosure formed between a convex shaped, isothermal heated body and its concave shaped, surrounding isothermal enclosure is presented. An experimental test program is conducted at atmospheric and reduced pressure conditions using a transient measurement technique for various enclosure configurations, including concentric cubes, cube-in-sphere, sphere-in-cube, and other geometries. Measurements are reported for a wide range of Rayleigh number, including the diffusive limit. An analytical modeling procedure is developed based on a composite solution of three asymptotic relationships, the conduction limit, the laminar boundary layer and transition flow convective limits. The composite model is in excellent agreement with the data, with an average RMS difference of 2–7% for all enclosure configurations and test conditions.Copyright © 2004 by ASME