The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform

Yitung Chen - One of the best experts on this subject based on the ideXlab platform.

  • Optimal design of a concentric Heat Exchanger for High-Temperature systems using CFD simulations
    Applied Thermal Engineering, 2015
    Co-Authors: Tzu-chen Hung, Hung-chien Chen, Duen-sheng Lee, Yitung Chen
    Abstract:

    Abstract Computational fluid dynamics (CFD) has been successfully used to simulate a three-dimensional concentric high temperature Heat Exchanger. The concentric shell with staggered fin arrays connecting serve not only as a part of the shell structure, but also as a flow-disturbing mechanism in an attempt to enhance Heat transfer. This Heat Exchanger uses helium gas and molten salt as hot and cold streams respectively in a counter-flow mode. Flow fields and Heat transfer characteristics of the two concentric channels are examined extensively. A design with an optimal performance of the Heat Exchanger is achieved by maximizing the effectiveness of the Heat Exchanger (e-NTU method) using the following parameters as optimizing variables: the width of the flow channel, the length, pitch, thickness, and angle of the fins. The number of CFD simulation are substantially reduced by Taguchi method, and the optimal configurations of the concentric high temperature Heat Exchanger are found with a channel width of 1 mm, a fin length of 11 mm, an angle of fin of 2.6°, and a fin thickness of 1.125 mm.

  • Stress analysis of internally finned bayonet tube in a high temperature Heat Exchanger
    Applied Thermal Engineering, 2012
    Co-Authors: Yitung Chen, Min Zeng, Qiu Wang Wang
    Abstract:

    Abstract In this paper, the thermal stress and deformation of the internally finned bayonet tube used for high temperature Heat Exchangers are presented. The internally finned bayonet tube is developed from the traditional bayonet tube, where the longitudinal plain fins are proposed to be welded on the inner surface of outer tube to enhance the Heat transfer performance. However, significant temperature gradient is observed along both the axial and radial directions. The large stress is still generated in the joint of inner fin and inner tube, and the joint of inner fin and outer tube due to the discontinuous change of the structure, although the bayonet structure has a great potential to reduce the stress. Therefore, the inner fin and inner tube are proposed to not be welded together so that they can expand or contract freely and the expansion does not affect each other. The effect of gap between inner tube and inner fin on the stress and Heat transfer performances is compared. The result indicates that the gap between them should be less than 1 mm for considered bayonet tube with 6 mm annulus height according to the coupled consideration of Heat transfer and stress performances.

  • CFD modeling and experimental validation of sulfur trioxide decomposition in bayonet type Heat Exchanger and chemical decomposer for different packed bed designs
    International Journal of Hydrogen Energy, 2009
    Co-Authors: Vijaisri Nagarajan, Valery Ponyavin, Yitung Chen, Milton E. Vernon, Paul S. Pickard, Anthony Hechanova
    Abstract:

    Abstract The growth of global energy demand during the 21st century, combined with the necessity to master greenhouse gas emissions has lead to the introduction of a new and universal energy carrier: hydrogen. The Department of Energy (DOE) Nuclear Hydrogen Initiative was investigating thermochemical cycles for hydrogen production using High-Temperature Heat Exchangers. In this study a three-dimensional computational model of High-Temperature Heat Exchanger and decomposer for decomposition of sulfur trioxide by the sulfur–iodine thermochemical water-splitting cycle with different packed bed designs has been done. The decomposer region of the bayonet Heat Exchanger also called as silicon carbide integrated decomposer (SID) is designed as the packed bed region. Cylindrical, spherical, cubical and hollow cylindrical pellets have been arranged inside the packed bed. The engineering design of the packed bed was very much influenced by the structure of the packing matrix, which was governed by the shape, dimension and the loading of the constituent particles. Staggered and regular packing methods are used for packing the pellets in the packed bed region. The numerical model is created using GAMBIT and fluid, thermal and chemical analyses were performed using FLUENT. The decomposition percentage of sulfur trioxide is found for the packed bed region with different pellets and the numerical results obtained is compared with the experimental results. A comparison is made for the decomposition percentage of SO 3 for the packed bed approach and the porous media approach.

  • Numerical modeling of compact high temperature Heat Exchanger and chemical decomposer for hydrogen production
    Heat and Mass Transfer, 2008
    Co-Authors: Valery Ponyavin, Anthony E. Hechanova, Yitung Chen, Merrill Wilson
    Abstract:

    The present study addresses fluid flow and Heat transfer in a high temperature compact Heat Exchanger which will be used as a chemical decomposer in a hydrogen production plant. The Heat Exchanger is manufactured using fused ceramic layers that allow creation of channels with dimensions below 1 mm. The main purpose of this study is to increase the thermal performance of the Heat Exchanger, which can help to increase the sulfuric acid decomposition rate. Effects of various channel geometries of the Heat Exchanger on the pressure drop are studied as well. A three-dimensional computational model is developed for the investigation of fluid flow and Heat transfer in the Heat Exchanger. Several different geometries of the Heat Exchanger channels, such as straight channels, ribbed ground channels, hexagonal channels, and diamond-shaped channels are examined. Based on the results, methods on how to improve the design of the Heat Exchanger are recommended.

  • Calculation of Fluid Flow Distribution Inside a Compact Ceramic High Temperature Heat Exchanger and Chemical Decomposer
    Journal of Fluids Engineering, 2008
    Co-Authors: Valery Ponyavin, James Cutts, Merrill Wilson, Yitung Chen, Anthony Hechanova
    Abstract:

    Numerical analysis of flow distribution inside a compact ceramic high temperature Heat Exchanger and chemical decomposer (thereafter, Heat Exchanger), which will be used for hydrogen production, wherein the sulfur iodine thermochemical cycle is performed. To validate the numerical model, experimental investigation of the Heat Exchanger is accomplished. The study of the flow distribution in the base line design Heat Exchanger shows that the design has large-flow maldistribution and the reverse flow may occur at poor inlet and outlet manifold configurations. To enhance uniformity of the flow rate distribution among the Heat Exchanger internal channels, several improved designs of the Heat Exchanger manifolds and supply channels are proposed. The proposed designs have a sufficiently uniform flow rate distribution among the internal channels, with an appropriate pressure drop.

C.j. Bates - One of the best experts on this subject based on the ideXlab platform.

  • COHEX: a computer model for solving the thermal energy exchange in an ultra high temperature Heat Exchanger. Part B: validation and results
    Applied Thermal Engineering, 1999
    Co-Authors: A.j. Jolly, Timothy O'doherty, C.j. Bates
    Abstract:

    Abstract The paper reports the development of a computer program that solves the thermal energy exchange and pressure drop characteristics for bayonet-element Heat Exchangers. The prime motivation for the study was to aid the design of a Heat Exchanger for the externally-fired combined cycle (EFCC) energy generation process. The essential feature of this high-efficiency process is the CMC (ceramic matrix composite) bayonet-tube gas–gas Heat Exchanger for use with shell-side temperatures up to 1600°C. It is envisaged that similar Heat Exchangers can be designed for applications in the metallic extraction and production industries. The program, named COHEX (composite Heat Exchanger), solves the basic governing equations of the Exchanger. It makes use of a numerical iterative approach from an initial tube-side outlet temperature estimate to converge to a solution. For given inlet conditions, the program evaluates the Heat transfer between the shell-side and tube-side streams and arrives at the outlet conditions. This two-part paper presents a computational solution method using accepted techniques for conduction, convection and radiation in the high temperature Heat Exchanger. Part A addresses the technological background of the EFCC application and the theoretical content of COHEX in terms of accuracy and sophistication of the code. The second part of this paper reported here, part B, describes the experimental facilities used to gather data in order to validate the program output. A comparison of computed and experimental data is presented. The paper progresses to illustrate the effects of parameter variation on Heat Exchanger output.

  • COHEX: a computer model for solving the thermal energy exchange in an ultra high temperature Heat Exchanger. Part A: computational theory
    Applied Thermal Engineering, 1998
    Co-Authors: A.j. Jolly, Timothy O'doherty, C.j. Bates
    Abstract:

    Abstract The paper reports the development of a computer program that solves the thermal energy exchange and pressure drop characteristics for bayonet-element Heat Exchangers. The prime motivation for the study was to aid the design of a Heat Exchanger for the externally-fired combined cycle (EFCC) energy generation process. The essential feature of this high-efficiency process is the ceramic bayonet-tube gas–gas Heat Exchanger for use with shell-side temperatures up to 1600°C. It is envisaged that similar Heat Exchangers can be designed for applications in the metallic extraction and production industries. The program, named COHEX ( C omposite H eat E xchanger), solves the basic governing equations of the Exchanger. It makes use of a numerical iterative approach from an initial tube-side outlet temperature estimate to converge to a solution. For given inlet conditions, the program evaluates the Heat transfer between the shell-side and tube-side streams and arrives at the outlet conditions. This two-part paper presents a computational solution method using accepted techniques for conduction, convection and radiation in the ceramic Heat Exchanger. Part A addresses the technological background of the EFCC application and the theoretical content of COHEX in terms of accuracy and sophistication of the code. The second part of this paper, part B, describes the experimental facilities used to gather data in order to validate the program output. A comparison of computed and experimental data is presented. The paper progresses to illustrate the effects of parameter variation on Heat Exchanger output.

Anthony Hechanova - One of the best experts on this subject based on the ideXlab platform.

  • CFD modeling and experimental validation of sulfur trioxide decomposition in bayonet type Heat Exchanger and chemical decomposer for different packed bed designs
    International Journal of Hydrogen Energy, 2009
    Co-Authors: Vijaisri Nagarajan, Valery Ponyavin, Yitung Chen, Milton E. Vernon, Paul S. Pickard, Anthony Hechanova
    Abstract:

    Abstract The growth of global energy demand during the 21st century, combined with the necessity to master greenhouse gas emissions has lead to the introduction of a new and universal energy carrier: hydrogen. The Department of Energy (DOE) Nuclear Hydrogen Initiative was investigating thermochemical cycles for hydrogen production using High-Temperature Heat Exchangers. In this study a three-dimensional computational model of High-Temperature Heat Exchanger and decomposer for decomposition of sulfur trioxide by the sulfur–iodine thermochemical water-splitting cycle with different packed bed designs has been done. The decomposer region of the bayonet Heat Exchanger also called as silicon carbide integrated decomposer (SID) is designed as the packed bed region. Cylindrical, spherical, cubical and hollow cylindrical pellets have been arranged inside the packed bed. The engineering design of the packed bed was very much influenced by the structure of the packing matrix, which was governed by the shape, dimension and the loading of the constituent particles. Staggered and regular packing methods are used for packing the pellets in the packed bed region. The numerical model is created using GAMBIT and fluid, thermal and chemical analyses were performed using FLUENT. The decomposition percentage of sulfur trioxide is found for the packed bed region with different pellets and the numerical results obtained is compared with the experimental results. A comparison is made for the decomposition percentage of SO 3 for the packed bed approach and the porous media approach.

  • High Temperature Heat Exchanger Project
    2008
    Co-Authors: Anthony Hechanova
    Abstract:

    The UNLV Research Foundation assembled a research consortium for high temperature Heat Exchanger design and materials compatibility and performance comprised of university and private industry partners under the auspices of the US DOE-NE Nuclear Hydrogen Initiative in October 2003. The objectives of the consortium were to conduct investigations of candidate materials for high temperature Heat Exchanger componets in hydrogen production processes and design and perform prototypical testing of Heat Exchangers. The initial research of the consortium focused on the intermediate Heat Exchanger (located between the nuclear reactor and hydrogen production plan) and the components for the hydrogen iodine decomposition process and sulfuric acid decomposition process. These Heat Exchanger components were deemed the most challenging from a materials performance and compatibility perspective

  • Calculation of Fluid Flow Distribution Inside a Compact Ceramic High Temperature Heat Exchanger and Chemical Decomposer
    Journal of Fluids Engineering, 2008
    Co-Authors: Valery Ponyavin, James Cutts, Merrill Wilson, Yitung Chen, Anthony Hechanova
    Abstract:

    Numerical analysis of flow distribution inside a compact ceramic high temperature Heat Exchanger and chemical decomposer (thereafter, Heat Exchanger), which will be used for hydrogen production, wherein the sulfur iodine thermochemical cycle is performed. To validate the numerical model, experimental investigation of the Heat Exchanger is accomplished. The study of the flow distribution in the base line design Heat Exchanger shows that the design has large-flow maldistribution and the reverse flow may occur at poor inlet and outlet manifold configurations. To enhance uniformity of the flow rate distribution among the Heat Exchanger internal channels, several improved designs of the Heat Exchanger manifolds and supply channels are proposed. The proposed designs have a sufficiently uniform flow rate distribution among the internal channels, with an appropriate pressure drop.

  • Fluid/Thermal Analysis of High Temperature Heat Exchanger and Chemical Decomposer for Hydrogen Production
    ASME JSME 2007 Thermal Engineering Heat Transfer Summer Conference Volume 2, 2007
    Co-Authors: Valery Ponyavin, Yitung Chen, Anthony Hechanova, Merrill Anderson Wilson
    Abstract:

    This paper presents fluid flow and Heat transfer study of a high temperature Heat Exchanger and chemical decomposer. The decomposer will be used as a part of the plant for hydrogen production. The decomposer is manufactured using fused ceramic layers that allow creation of channels with dimensions below one millimeter. The main purpose for this study is to increase thermal performance of the decomposer which can help to intensify sulfuric acid decomposition rate. Effects of using various channel geometries of the decomposer on the pressure drop are studied as well. A three-dimensional computational model is developed for the investigation of fluid flow and Heat transfer in the decomposer. Several different geometries of the decomposer channels such as straight channels, ribbed ground channels, hexagonal channels, and diamond-shaped channels are examined. Based on results of the calculation, the recommendations for the improved design of the decomposer are obtained.Copyright © 2007 by ASME

  • Transient Analysis of a Ceramic High Temperature Heat Exchanger and Chemical Decomposer
    Volume 3: Design and Manufacturing, 2007
    Co-Authors: Valery Ponyavin, Mohamed B Trabia, Yitung Chen, Taha Mohamed, Anthony Hechanova
    Abstract:

    Ceramics are suitable for use in high temperature applications as well as corrosive environment. These characteristics were the reason behind selection silicone carbide for a high temperature Heat Exchanger and chemical decomposer, which is a part of the Sulphur-Iodine (SI) thermo-chemical cycle. The Heat Exchanger is expected to operate in the range of 950°C. The proposed design is manufactured using fused ceramic layers that allow creation of micro-channels with dimensions below one millimeter. A proper design of the Heat exchanges requires considering possibilities of failure due to stresses under both steady state and transient conditions. Temperature gradients within the Heat Exchanger ceramic components induce thermal stresses that dominate other stresses. A three-dimensional computational model is developed to investigate the fluid flow, Heat transfer and stresses in the decomposer. Temperature distribution in the solid is imported to finite element software and used with pressure loads for stress analysis. The stress results are used to calculate probability of failure based on Weibull failure criteria. Earlier analysis showed that stress results at steady state operating conditions are satisfactory. The focus of this paper is to consider stresses that are induced during transient scenarios. In particular, the cases of startup and shutdown of the Heat Exchanger are considered. The paper presents an evaluation of the stresses in these two cases.

Qiu Wang Wang - One of the best experts on this subject based on the ideXlab platform.

  • Design and optimization of a novel high temperature Heat Exchanger for waste Heat cascade recovery from exhaust flue gases
    Energy, 2018
    Co-Authors: Pan Zhang, Guang Yu Ma, Wei-dong Li, Ting Ma, Qiu Wang Wang
    Abstract:

    The waste Heat of high temperature exhaust flue gases is widely distributed in many industrial processes. Recovery of waste Heat is of great significance to energy saving and sustainability. In this paper, a novel high temperature Heat Exchanger with hybrid enhancement technologies is proposed to improve waste Heat recovery efficiency based on the cascade recovery and utilization method. Algorithm for HTHE structural design and optimization is developed and verified according to the experimental results. Heat transfer and pressure drop performance of the proposed HTHE are estimated by using the algorithm. The results show that the effectiveness of the proposed HTHE increases as the gas temperature increases and mass flow rate decreases. Average effectiveness of the proposed HTHE and temperature of preHeated air are 12.5% and 85.8 °C higher than those of traditional HTHE with additional 70.0% and 22.0% pressure drop on air and gas sides, respectively. The structural optimization of the proposed HTHE is carried out and it shows that the optimized HTHE has better Heat transfer capacity and comprehensive performance under identical pressure drop, increasing effectiveness by 12.6% without enlarging pressure drop compared with the non-optimized HTHE.

  • improvements on maldistribution of a high temperature multi channel compact Heat Exchanger by different inlet baffles
    Energy, 2014
    Co-Authors: Wenxiao Chu, Min Zeng, Liangbi Wang, Qiu Wang Wang
    Abstract:

    Abstract The multi-channels plate Heat Exchangers are recommended to be used in the high-efficiency power and propulsion systems. The present study analyzes the large fluid flow maldistribution occurring at the inlet manifold configurations of a high temperature Heat Exchanger with CFD (computational fluid dynamics) method. Four modified inlet manifolds are proposed, including inclined baffle, segmental baffle, helical baffle and improved helical baffle. It turns out that all the proposed designs have more or less improvement of uniform flow distribution among each channel. By comparing the flow nonuniformity, the Nusselt number and the friction factor, the inlet manifold with equidifferent helical baffles is the best, whose flow nonuniformity can be decreased by 52% averagely. Comparing with the baseline design, meanwhile, the optimal modified design which inducts the spiral fluid flow has effect on the comprehensive performance. The Nusselt number can be increased by 24% averagely due to the produced spiral fluid flow while the pressure drop is in an acceptable range. Furthermore, the corresponding correlation of Nu and f are obtained according to CFD results.

  • effect of lateral fin profiles on stress performance of internally finned tubes in a high temperature Heat Exchanger
    Applied Thermal Engineering, 2013
    Co-Authors: Min Zeng, Mohamed B Trabia, Bengt Sunden, Qiu Wang Wang
    Abstract:

    The thermal stress of the internally finned bayonet tube used for high temperature Heat Exchangers is numerically investigated by ANSYS software. Three kinds of lateral fin profiles, namely Z-shape, S-shape and V-shape are studied and compared. The significant temperature gradient and largest Von Mises stress are acquired. The largest stress is still generated in the joint of inner fin and outer tube due to the discontinuous change of the structure. The inner fin and inner tube are proposed to not be welded together to meet the reliability. The Z-shape has the best performance in both Heat transfer and reliability, and is recommended for engineering application in high temperature Heat Exchangers. (C) 2012 Elsevier Ltd. All rights reserved.

  • Stress analysis of internally finned bayonet tube in a high temperature Heat Exchanger
    Applied Thermal Engineering, 2012
    Co-Authors: Yitung Chen, Min Zeng, Qiu Wang Wang
    Abstract:

    Abstract In this paper, the thermal stress and deformation of the internally finned bayonet tube used for high temperature Heat Exchangers are presented. The internally finned bayonet tube is developed from the traditional bayonet tube, where the longitudinal plain fins are proposed to be welded on the inner surface of outer tube to enhance the Heat transfer performance. However, significant temperature gradient is observed along both the axial and radial directions. The large stress is still generated in the joint of inner fin and inner tube, and the joint of inner fin and outer tube due to the discontinuous change of the structure, although the bayonet structure has a great potential to reduce the stress. Therefore, the inner fin and inner tube are proposed to not be welded together so that they can expand or contract freely and the expansion does not affect each other. The effect of gap between inner tube and inner fin on the stress and Heat transfer performances is compared. The result indicates that the gap between them should be less than 1 mm for considered bayonet tube with 6 mm annulus height according to the coupled consideration of Heat transfer and stress performances.

A.j. Jolly - One of the best experts on this subject based on the ideXlab platform.

  • COHEX: a computer model for solving the thermal energy exchange in an ultra high temperature Heat Exchanger. Part B: validation and results
    Applied Thermal Engineering, 1999
    Co-Authors: A.j. Jolly, Timothy O'doherty, C.j. Bates
    Abstract:

    Abstract The paper reports the development of a computer program that solves the thermal energy exchange and pressure drop characteristics for bayonet-element Heat Exchangers. The prime motivation for the study was to aid the design of a Heat Exchanger for the externally-fired combined cycle (EFCC) energy generation process. The essential feature of this high-efficiency process is the CMC (ceramic matrix composite) bayonet-tube gas–gas Heat Exchanger for use with shell-side temperatures up to 1600°C. It is envisaged that similar Heat Exchangers can be designed for applications in the metallic extraction and production industries. The program, named COHEX (composite Heat Exchanger), solves the basic governing equations of the Exchanger. It makes use of a numerical iterative approach from an initial tube-side outlet temperature estimate to converge to a solution. For given inlet conditions, the program evaluates the Heat transfer between the shell-side and tube-side streams and arrives at the outlet conditions. This two-part paper presents a computational solution method using accepted techniques for conduction, convection and radiation in the high temperature Heat Exchanger. Part A addresses the technological background of the EFCC application and the theoretical content of COHEX in terms of accuracy and sophistication of the code. The second part of this paper reported here, part B, describes the experimental facilities used to gather data in order to validate the program output. A comparison of computed and experimental data is presented. The paper progresses to illustrate the effects of parameter variation on Heat Exchanger output.

  • COHEX: a computer model for solving the thermal energy exchange in an ultra high temperature Heat Exchanger. Part A: computational theory
    Applied Thermal Engineering, 1998
    Co-Authors: A.j. Jolly, Timothy O'doherty, C.j. Bates
    Abstract:

    Abstract The paper reports the development of a computer program that solves the thermal energy exchange and pressure drop characteristics for bayonet-element Heat Exchangers. The prime motivation for the study was to aid the design of a Heat Exchanger for the externally-fired combined cycle (EFCC) energy generation process. The essential feature of this high-efficiency process is the ceramic bayonet-tube gas–gas Heat Exchanger for use with shell-side temperatures up to 1600°C. It is envisaged that similar Heat Exchangers can be designed for applications in the metallic extraction and production industries. The program, named COHEX ( C omposite H eat E xchanger), solves the basic governing equations of the Exchanger. It makes use of a numerical iterative approach from an initial tube-side outlet temperature estimate to converge to a solution. For given inlet conditions, the program evaluates the Heat transfer between the shell-side and tube-side streams and arrives at the outlet conditions. This two-part paper presents a computational solution method using accepted techniques for conduction, convection and radiation in the ceramic Heat Exchanger. Part A addresses the technological background of the EFCC application and the theoretical content of COHEX in terms of accuracy and sophistication of the code. The second part of this paper, part B, describes the experimental facilities used to gather data in order to validate the program output. A comparison of computed and experimental data is presented. The paper progresses to illustrate the effects of parameter variation on Heat Exchanger output.