The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Hari B. Vuthaluru - One of the best experts on this subject based on the ideXlab platform.

  • Novel predictive tools for design of radiant and convective sections of direct fired heaters
    Applied Energy, 2010
    Co-Authors: Alireza Bahadori, Hari B. Vuthaluru
    Abstract:

    Direct fired heaters are used considerably in the energy related industries and petroleum industries for heating crude oil in the petroleum refining and petrochemical sectors. The aim of the current study is to formulate simple-to-use correlations to design the radiant and convective sections of direct fired heaters. The developed tools are easier than currently available models and involves a fewer number of parameters, requiring less complicated and shorter computations. Firstly, a simple correlation is developed to provide an accurate and rapid prediction of the absorbed heat in the radiant section of a fired heater, expressed as a fraction of the total net heat liberation, in terms of the average heat flux to the tubes, the arrangement of the tubes (circumferential), and the air to fuel mass ratio. Secondly, another simple correlation is developed to approximate external heat transfer coefficients for 75, 100, and 150Â mm Nominal Pipe Size (NPS) steel Pipes arranged in staggered rows and surrounded by combustion gases. Finally, a simple correlation is presented to predict the gross thermal efficiency as a function of percent excess air and stack gas temperature. This study shows that the proposed method has a good agreement with the available reliable data in the literature. The average absolute deviations between reported data and the proposed correlations are found to be around 1.5% demonstrating the excellent performance of proposed predictive tool. The proposed simple-to-use method can be of significant practical value for the engineers and scientists to have a quick check on the design of radiant and convective sections of direct fired heater. In particular, mechanical and process engineers would find the proposed approach to be user-friendly involving no complex expressions with transparent and easy to understand calculations.

  • Predictive tool for estimation of convection heat transfer coefficients and efficiencies for finned tubular sections
    International Journal of Thermal Sciences, 2010
    Co-Authors: Alireza Bahadori, Hari B. Vuthaluru
    Abstract:

    Abstract Fins or extended surfaces are widely used to increase the air side heat transfer rate in various heat exchange applications. In this paper, firstly, an attempt has been made to formulate a novel and simple-to-use correlation for the prediction of efficiencies for uniform thickness finned tubular sections as well as fin tip temperature for wide range of conditions (covering finned Pipe diameter to Pipe diameter ratios of up to 3). Secondly, another simple correlation is developed to approximate external convection heat transfer coefficients for Nominal Pipe Size (NPS) steel Pipes of 75, 100, and 150 mm arranged in staggered rows surrounded by combustion gases for temperature up to 600 °C and gas mass flow rates of up to 3 kg/(m2 s). A simple interpolation formula generalizes this correlation for wide range of steel Pipes. Average absolute deviations between the reported data and the proposed correlations are found to be around 1% demonstrating the excellent performance of proposed correlation. The tool developed in this study can be of immense practical value for engineers and scientists to have a quick check on the efficiencies for uniform thickness finned tubular sections as well as external convection heat transfer coefficients for various steel Pipes arranged in staggered rows and surrounded by combustion gases flowing externally to heat a liquid in a Pipe at various conditions without opting for any experimental measurements. In particular, practice engineers would find the predictive tool to be user-friendly with transparent calculations involving no complex expressions.

Alireza Bahadori - One of the best experts on this subject based on the ideXlab platform.

  • Novel predictive tools for design of radiant and convective sections of direct fired heaters
    Applied Energy, 2010
    Co-Authors: Alireza Bahadori, Hari B. Vuthaluru
    Abstract:

    Direct fired heaters are used considerably in the energy related industries and petroleum industries for heating crude oil in the petroleum refining and petrochemical sectors. The aim of the current study is to formulate simple-to-use correlations to design the radiant and convective sections of direct fired heaters. The developed tools are easier than currently available models and involves a fewer number of parameters, requiring less complicated and shorter computations. Firstly, a simple correlation is developed to provide an accurate and rapid prediction of the absorbed heat in the radiant section of a fired heater, expressed as a fraction of the total net heat liberation, in terms of the average heat flux to the tubes, the arrangement of the tubes (circumferential), and the air to fuel mass ratio. Secondly, another simple correlation is developed to approximate external heat transfer coefficients for 75, 100, and 150Â mm Nominal Pipe Size (NPS) steel Pipes arranged in staggered rows and surrounded by combustion gases. Finally, a simple correlation is presented to predict the gross thermal efficiency as a function of percent excess air and stack gas temperature. This study shows that the proposed method has a good agreement with the available reliable data in the literature. The average absolute deviations between reported data and the proposed correlations are found to be around 1.5% demonstrating the excellent performance of proposed predictive tool. The proposed simple-to-use method can be of significant practical value for the engineers and scientists to have a quick check on the design of radiant and convective sections of direct fired heater. In particular, mechanical and process engineers would find the proposed approach to be user-friendly involving no complex expressions with transparent and easy to understand calculations.

  • Predictive tool for estimation of convection heat transfer coefficients and efficiencies for finned tubular sections
    International Journal of Thermal Sciences, 2010
    Co-Authors: Alireza Bahadori, Hari B. Vuthaluru
    Abstract:

    Abstract Fins or extended surfaces are widely used to increase the air side heat transfer rate in various heat exchange applications. In this paper, firstly, an attempt has been made to formulate a novel and simple-to-use correlation for the prediction of efficiencies for uniform thickness finned tubular sections as well as fin tip temperature for wide range of conditions (covering finned Pipe diameter to Pipe diameter ratios of up to 3). Secondly, another simple correlation is developed to approximate external convection heat transfer coefficients for Nominal Pipe Size (NPS) steel Pipes of 75, 100, and 150 mm arranged in staggered rows surrounded by combustion gases for temperature up to 600 °C and gas mass flow rates of up to 3 kg/(m2 s). A simple interpolation formula generalizes this correlation for wide range of steel Pipes. Average absolute deviations between the reported data and the proposed correlations are found to be around 1% demonstrating the excellent performance of proposed correlation. The tool developed in this study can be of immense practical value for engineers and scientists to have a quick check on the efficiencies for uniform thickness finned tubular sections as well as external convection heat transfer coefficients for various steel Pipes arranged in staggered rows and surrounded by combustion gases flowing externally to heat a liquid in a Pipe at various conditions without opting for any experimental measurements. In particular, practice engineers would find the predictive tool to be user-friendly with transparent calculations involving no complex expressions.

Hany F. Abdalla - One of the best experts on this subject based on the ideXlab platform.

  • Shakedown Boundary and Limit Load Determination of a 90-Degree Back to Back Pipe Bend Subjected to Steady Internal Perssures and Cyclic In-Plane Bending Moments
    Volume 3: Design and Analysis, 2013
    Co-Authors: Hany F. Abdalla
    Abstract:

    Shakedown analysis of 90–degree back–to–back Pipe bends is scarce within open literature. According the author’s knowledge, no shakedown analysis exists for such structure based on experimental data. Ninety degree back–to–back Pipe bends are extensively utilized within piping networks of nuclear submarines and modern turbofan aero–engines where space limitation is considered a paramount concern. Additionally, on larger scales, 90–degree back–to–back Pipe bend configurations are also found within piping networks of huge liquefied natural gas tankers. The structure analyzed is formed by bending a straight Pipe to acquire the geometry of two 90–degree Pipe bends set back–to–back each having a Nominal Pipe Size (NPS) of 10 in. Schedule 40 Standard (STD). In the current research, the 90–degree back–to–back Pipe bend setup analyzed is subjected to a spectrum of steady internal pressures and cyclic in–plane bending moments. A previously developed simplified technique for determining elastic shakedown limit loads is utilized to generate the elastic shakedown boundary of the 90–degree back–to–back Pipe bend analyzed. In addition to determining the elastic shakedown boundary, elastic and post shakedown domains (Bree diagram), the maximum moment carrying capacities (limit moments) are also determined and imposed on the generated Bree diagram of the analyzed structure. The simplified technique outcomes showed excellent correlation with the results of full elastic–plastic cyclic loading finite element simulations.Copyright © 2013 by ASME

  • Shakedown Limit Loads for 90 Degree Scheduled Pipe Bends Subjected to Steady Internal Pressure and Cyclic Bending Moments
    Journal of Pressure Vessel Technology-transactions of The Asme, 2011
    Co-Authors: Hany F. Abdalla, Mohammad M. Megahed, Maher Y A Younan
    Abstract:

    A simplified technique for determining the shakedown limit load for a long radius 90 deg Pipe bend was previously developed (Abdalla, H. F., et al., 2006, "Determination of Shakedown Limit Load for a 90 Degree Pipe Bend Using a Simplified Technique, "ASME J. Pressure Vessel Technol., 128, pp. 618-624; Abdalla, H. F., et al., 2007, "Shakedown Limits of a 90-Degree Pipe Bend Using Small and Large Displacement Formulations," ASME J. Pressure Vessel Technol., 129, pp. 287-295). The simplified technique utilizes the finite element (FE) method and employs the small displacement formulation to determine the shakedown limit load (moment) without performing lengthy time consuming full cyclic loading finite element simulations or utilizing conventional iterative elastic techniques. The shakedown limit load is determined through the calculation of residual stresses developed within the Pipe bend structure. In the current paper, a parametric study is conducted through applying the simplified technique on three scheduled Pipe bends, namely, Nominal Pipe Size (NPS) 10 in. Sch. 20, NPS 10 in. Sch. 40 STD, and NPS 10 in. Sch. 80. Two material models are assigned, namely, an elastic perfectly plastic (EPP) material and an idealized elastic-linear strain hardening material obeying Ziegler's linear kinematic hardening (KH) rule. This type of material model is termed in the current study as the KH-material. The Pipe bends are subjected to a spectrum of steady internal pressure magnitudes and cyclic bending moments. The cyclic bending includes three different loading patterns, namely, in-plane closing, in-plane opening, and out-of-plane bending moment loadings of the Pipe bends. The shakedown limit moments outputted by the simplified technique are used to generate shakedown diagrams of the scheduled Pipe bends for the spectrum of steady internal pressure magnitudes. A comparison between the generated shakedown diagrams for the Pipe bends employing the EPP- and the KH-materials is presented. Relatively higher shakedown limit moments were recorded for the Pipe bends employing the KH-material at the medium to high internal pressure magnitudes.

  • Shakedown Limit Loads for 90-Degree Scheduled Pipe Bends Subjected to Constant Internal Pressure and Cyclic Bending Moments
    Volume 3: Design and Analysis, 2008
    Co-Authors: Hany F. Abdalla, Mohammad M. Megahed, Maher Y A Younan
    Abstract:

    A simplified technique for determining the shakedown limit load for a long radius 90-degree Pipe bend was previously developed [1, 2]. The simplified technique utilizes the finite element method and employs the small displacement formulation to determine the shakedown limit load (moment) without performing lengthy time consuming full cyclic loading finite element simulations or utilizing conventional iterative elastic techniques. The shakedown limit load is determined through the calculation of residual stresses developed within the Pipe bend structure. In the current paper, a parametric study is conducted through applying the simplified technique on three scheduled Pipe bends namely: NPS (Nominal Pipe Size) 10" Sch. No. 20, NPS 10" Sch. No. 40 STD, and NPS 10" Sch. No. 80. Two material models are assigned namely; an elastic-perfectly-plastic (EPP) material and an idealized elastic-linear strain hardening material obeying Ziegler’s linear kinematic hardening (KH) rule. This type of material model is termed in the current study as the KH-material. The Pipe bends are subjected to a spectrum of constant internal pressure magnitudes and cyclic bending moments. The cyclic bending includes three different loading patterns namely: in-plane closing (IPC), in-plane opening (IPO), and out-of-plane (OP) bending moment loadings of the Pipe bends. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the scheduled Pipe bends for the spectrum of constant internal pressure magnitudes. A comparison between the generated shakedown diagrams for the Pipe bends employing the EPP- and the KH-materials is presented. Relatively higher shakedown limit moments were recorded for the Pipe bends employing the KH-material at the medium to high internal pressure magnitudes.© 2008 ASME

Maher Y A Younan - One of the best experts on this subject based on the ideXlab platform.

  • Shakedown Limit Loads for 90 Degree Scheduled Pipe Bends Subjected to Steady Internal Pressure and Cyclic Bending Moments
    Journal of Pressure Vessel Technology-transactions of The Asme, 2011
    Co-Authors: Hany F. Abdalla, Mohammad M. Megahed, Maher Y A Younan
    Abstract:

    A simplified technique for determining the shakedown limit load for a long radius 90 deg Pipe bend was previously developed (Abdalla, H. F., et al., 2006, "Determination of Shakedown Limit Load for a 90 Degree Pipe Bend Using a Simplified Technique, "ASME J. Pressure Vessel Technol., 128, pp. 618-624; Abdalla, H. F., et al., 2007, "Shakedown Limits of a 90-Degree Pipe Bend Using Small and Large Displacement Formulations," ASME J. Pressure Vessel Technol., 129, pp. 287-295). The simplified technique utilizes the finite element (FE) method and employs the small displacement formulation to determine the shakedown limit load (moment) without performing lengthy time consuming full cyclic loading finite element simulations or utilizing conventional iterative elastic techniques. The shakedown limit load is determined through the calculation of residual stresses developed within the Pipe bend structure. In the current paper, a parametric study is conducted through applying the simplified technique on three scheduled Pipe bends, namely, Nominal Pipe Size (NPS) 10 in. Sch. 20, NPS 10 in. Sch. 40 STD, and NPS 10 in. Sch. 80. Two material models are assigned, namely, an elastic perfectly plastic (EPP) material and an idealized elastic-linear strain hardening material obeying Ziegler's linear kinematic hardening (KH) rule. This type of material model is termed in the current study as the KH-material. The Pipe bends are subjected to a spectrum of steady internal pressure magnitudes and cyclic bending moments. The cyclic bending includes three different loading patterns, namely, in-plane closing, in-plane opening, and out-of-plane bending moment loadings of the Pipe bends. The shakedown limit moments outputted by the simplified technique are used to generate shakedown diagrams of the scheduled Pipe bends for the spectrum of steady internal pressure magnitudes. A comparison between the generated shakedown diagrams for the Pipe bends employing the EPP- and the KH-materials is presented. Relatively higher shakedown limit moments were recorded for the Pipe bends employing the KH-material at the medium to high internal pressure magnitudes.

  • Shakedown Limit Loads for 90-Degree Scheduled Pipe Bends Subjected to Constant Internal Pressure and Cyclic Bending Moments
    Volume 3: Design and Analysis, 2008
    Co-Authors: Hany F. Abdalla, Mohammad M. Megahed, Maher Y A Younan
    Abstract:

    A simplified technique for determining the shakedown limit load for a long radius 90-degree Pipe bend was previously developed [1, 2]. The simplified technique utilizes the finite element method and employs the small displacement formulation to determine the shakedown limit load (moment) without performing lengthy time consuming full cyclic loading finite element simulations or utilizing conventional iterative elastic techniques. The shakedown limit load is determined through the calculation of residual stresses developed within the Pipe bend structure. In the current paper, a parametric study is conducted through applying the simplified technique on three scheduled Pipe bends namely: NPS (Nominal Pipe Size) 10" Sch. No. 20, NPS 10" Sch. No. 40 STD, and NPS 10" Sch. No. 80. Two material models are assigned namely; an elastic-perfectly-plastic (EPP) material and an idealized elastic-linear strain hardening material obeying Ziegler’s linear kinematic hardening (KH) rule. This type of material model is termed in the current study as the KH-material. The Pipe bends are subjected to a spectrum of constant internal pressure magnitudes and cyclic bending moments. The cyclic bending includes three different loading patterns namely: in-plane closing (IPC), in-plane opening (IPO), and out-of-plane (OP) bending moment loadings of the Pipe bends. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the scheduled Pipe bends for the spectrum of constant internal pressure magnitudes. A comparison between the generated shakedown diagrams for the Pipe bends employing the EPP- and the KH-materials is presented. Relatively higher shakedown limit moments were recorded for the Pipe bends employing the KH-material at the medium to high internal pressure magnitudes.© 2008 ASME

Tommy Precht - One of the best experts on this subject based on the ideXlab platform.

  • Repair of High Pressure Pipe Fittings Using Composite Materials
    2010 8th International Pipeline Conference Volume 3, 2010
    Co-Authors: Julian Bedoya, Christopher L. Alexander, Tommy Precht
    Abstract:

    Pipelines and piping frequently suffer from metal loss that threatens their integrity and serviceability. Multiple repair options exist for straight sections of Pipe; however, repair options for Pipe fittings such as elbows and tees are typically limited to composite repair systems, or section replacement. The latter method can be costly as it often requires at least a partial shut down of the Pipeline while the section is replaced. A composite repair system however, can be performed in place during operations at a greatly reduced cost. The main challenge with the composite repair system is the required demonstrated ability to restore integrity and serviceability to the same level as the original metal system. Over the past 10 years, Stress Engineering Services, Inc. has been greatly involved in evaluating the ability of many composite repair systems to restore the original Pipeline structural integrity by testing methods and analysis methods. The current paper investigated the ability of the Armor Plate Pipe Wrap (APPW) system to restore the burst pressure of tee and elbow Pipe fittings with 60% metal loss to that of a Nominal thickness system. In this program four full scale burst tests were conducted: on 12-inch Nominal Pipe Size (NPS) Y52 tee and elbow Pipe fittings. All four fittings had 60% metal loss; two were repaired with APPW, and the other two were not repaired. Prior to burst testing, elastic plastic finite element analyses (FEA) were performed to adequately Size the repair thickness. The results of the FEA calculations predicted the restoration of the burst pressures of the repaired fittings up to a 1.6% agreement with the actual burst pressure results. Furthermore, the burst pressure of the 60% metal loss tee was increased from 3,059 psi (unrepaired) to 4,617 psi, or a 51% improvement. The burst pressure of the 60% metal loss elbow was increased from 2,610 psi to 4,625 psi, or a 77% improvement. Both the analysis and testing results demonstrated that composite materials can restore the pressure integrity of corroded tee and elbow Pipe fittings.Copyright © 2010 by ASME