Search

Search Results

• 11. [Article] An experimental investigation of natural convection heat transfer from an array of uniformly heated vertical cylinders to mercury

  An experimental investigation was conducted for natural convection heat transfer in an array of uniformly heated vertical cylinders in mercury. The test section consisted of seven electrically heated cylinders ...

  Citation × Citation Citation Abstract Copy Title: An experimental investigation of natural convection heat transfer from an array of uniformly heated vertical cylinders to mercury Author: Dutton, Jonathan Craig, 1951- An experimental investigation was conducted for natural convection heat transfer in an array of uniformly heated vertical cylinders in mercury. The test section consisted of seven electrically heated cylinders of 1.365 inch diameter and 3.825 inch heated length arranged in an equilateral triangular pattern. In order to preclude side flow effects, each seven pin bundle was surrounded by an enclosure tube with unheated half cylinders attached to the tube. Temperatures were measured with a stretched wire thermocouple probe which was designed to minimize flow disturbance effects. Four geometries were studied: the single vertical cylinder (P/D = ∞), and three bundle spacings, P/D = 1.5, 1.3, and 1.1, where P/D is the pitch-to-diameter ratio. The heat transfer results are presented in terms of the local Nusselt number and local modified Grashof number with the range on the Grashof number being 10⁵ < Gr[superscript *][subscript x] < 10¹⁰. The stretched wire probe results for the single cylinder are in agreement with those taken with an L-shaped probe and with previous experimental work. The bundle results were found to depend parametrically on both the heat flux and cylinder spacing. For the range investigated, the spacing effect was found to be much more significant than that of heat flux. The heat transfer results were found to depend significantly on circumferential position for P/D = 1.1, however circumferential dependence for the wider bundles was negligible. Rod-average correlations for the four geometries are also presented. The characteristics of the fluid temperature field were also studied. The trends observed in the mean temperature profiles for the various conditions are in agreement with those expected for this confined flow situation. In addition, fluctuations in the fluid temperatures were encountered and recorded. The trends shown by these disturbances are similar to those found for the previously studied vertical channel. The fluctuations were of largest amplitude for P/D = 1. 5, while those for P/D = 1.3 were slightly less severe, and those for the single cylinder and P/D = 1. 1 were negligible. The flow regimes thought to be encountered were the unstable laminar regime for P/D = 1.5 and 1.3, and the stable laminar one for the single cylinder and P/D = 1.1. Title: An experimental investigation of natural convection heat transfer from an array of uniformly heated vertical cylinders to mercury Author: Dutton, Jonathan Craig, 1951- An experimental investigation was conducted for natural convection heat transfer in an array of uniformly heated vertical cylinders in mercury. The test section consisted of seven electrically heated cylinders of 1.365 inch diameter and 3.825 inch heated length arranged in an equilateral triangular pattern. In order to preclude side flow effects, each seven pin bundle was surrounded by an enclosure tube with unheated half cylinders attached to the tube. Temperatures were measured with a stretched wire thermocouple probe which was designed to minimize flow disturbance effects. Four geometries were studied: the single vertical cylinder (P/D = ∞), and three bundle spacings, P/D = 1.5, 1.3, and 1.1, where P/D is the pitch-to-diameter ratio. The heat transfer results are presented in terms of the local Nusselt number and local modified Grashof number with the range on the Grashof number being 10⁵ < Gr[superscript *][subscript x] < 10¹⁰. The stretched wire probe results for the single cylinder are in agreement with those taken with an L-shaped probe and with previous experimental work. The bundle results were found to depend parametrically on both the heat flux and cylinder spacing. For the range investigated, the spacing effect was found to be much more significant than that of heat flux. The heat transfer results were found to depend significantly on circumferential position for P/D = 1.1, however circumferential dependence for the wider bundles was negligible. Rod-average correlations for the four geometries are also presented. The characteristics of the fluid temperature field were also studied. The trends observed in the mean temperature profiles for the various conditions are in agreement with those expected for this confined flow situation. In addition, fluctuations in the fluid temperatures were encountered and recorded. The trends shown by these disturbances are similar to those found for the previously studied vertical channel. The fluctuations were of largest amplitude for P/D = 1. 5, while those for P/D = 1.3 were slightly less severe, and those for the single cylinder and P/D = 1. 1 were negligible. The flow regimes thought to be encountered were the unstable laminar regime for P/D = 1.5 and 1.3, and the stable laminar one for the single cylinder and P/D = 1.1. Close

• 12. [Article] The effect of excess air on furnace wall temperature and heat transfer for natural gas combustion in a tubular heat exchanger

  Citation × Citation Citation Abstract Copy Title: The effect of excess air on furnace wall temperature and heat transfer for natural gas combustion in a tubular heat exchanger Author: Yu, Chia-ping Title: The effect of excess air on furnace wall temperature and heat transfer for natural gas combustion in a tubular heat exchanger Author: Yu, Chia-ping Close

• 13. [Article] Heat transfer in the splash-zone of a high temperature fluidized bed

  Citation × Citation Citation Abstract Copy Title: Heat transfer in the splash-zone of a high temperature fluidized bed Author: Pidwerbecki, David Title: Heat transfer in the splash-zone of a high temperature fluidized bed Author: Pidwerbecki, David Close

• 14. [Article] An analytic approach to temperature distribution in a thin-walled combustion chamber

  Citation × Citation Citation Abstract Copy Title: An analytic approach to temperature distribution in a thin-walled combustion chamber Author: Gorski, Saul Bogdan Title: An analytic approach to temperature distribution in a thin-walled combustion chamber Author: Gorski, Saul Bogdan Close

• 15. [Article] An experimental study of natural convection in air between a vertical isothermal flat plate and a parallel insulted flat plate

  The free convective heat transfer phenomena in air between two vertical plates 24 by 38 inches spaced 15.895 mm apart, was investigated in this experimental study. One plate was isothermal and, the other ...

  Citation × Citation Citation Abstract Copy Title: An experimental study of natural convection in air between a vertical isothermal flat plate and a parallel insulted flat plate Author: Lee, Soon Mo The free convective heat transfer phenomena in air between two vertical plates 24 by 38 inches spaced 15.895 mm apart, was investigated in this experimental study. One plate was isothermal and, the other adiabatic. A quartz fiber anomometer was used for measuring local velocities in the air between the vertical plates. A very fine iron-constantan thermocouple was used for local temperature measurements. Velocity and temperature profiles were obtained at several vertical positions along the plates. With the data obtained, local and mean convective heat transfer coefficients were determined at each vertical position. Title: An experimental study of natural convection in air between a vertical isothermal flat plate and a parallel insulted flat plate Author: Lee, Soon Mo The free convective heat transfer phenomena in air between two vertical plates 24 by 38 inches spaced 15.895 mm apart, was investigated in this experimental study. One plate was isothermal and, the other adiabatic. A quartz fiber anomometer was used for measuring local velocities in the air between the vertical plates. A very fine iron-constantan thermocouple was used for local temperature measurements. Velocity and temperature profiles were obtained at several vertical positions along the plates. With the data obtained, local and mean convective heat transfer coefficients were determined at each vertical position. Close

• 16. [Article] Nucleation and Heat Transfer in Liquid Nitrogen

  With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. ...

  Citation × Citation Citation Abstract Copy Title: Nucleation and Heat Transfer in Liquid Nitrogen Author: Roth, Eric Year: 1993 With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film/boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. Results, gained by plotting the system’s trajectory in the heat flux-temperature plane, are that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented. Title: Nucleation and Heat Transfer in Liquid Nitrogen Author: Roth, Eric Year: 1993 With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film/boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. Results, gained by plotting the system’s trajectory in the heat flux-temperature plane, are that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented. Close

• 17. [Article] Scaling of the Chinese HTR-PM Reactor Design for Licensing and Testing at the Oregon State University High Temperature Test Facility

  The United States (US) Department of Energy (DOE) has identified the pebble-bed reactor as a high priority for US research with the end goal of licensing a pebble-bed reactor (PBR) for operation in the ...

  Citation × Citation Citation Abstract Copy Title: Scaling of the Chinese HTR-PM Reactor Design for Licensing and Testing at the Oregon State University High Temperature Test Facility Author: Cox, Jordan (Jordan Tracy) The United States (US) Department of Energy (DOE) has identified the pebble-bed reactor as a high priority for US research with the end goal of licensing a pebble-bed reactor (PBR) for operation in the United States. Before this can be accomplished significant research must be done regarding the safety of the pebble-bed reactor. Of high interest is obtaining a better understanding of pebble-scale heat transfer and fluid flow within the PBR core. This thesis examines the ability of a hypothetical re-configured Oregon State University (OSU) High Temperature Test Facility (HTTF) to model the local phenomenon of the Chinese modular PBR (HTR-PM). Scaling analysis is used to quantify distortions that would occur between the HTR-PM and the scaled OSU HTTF. A one-fourth scaled test facility in height, core diameter, and pebble size is proposed. The scaling then demonstrates that this facility could model heat transfer, temperature profiles, and fluid forces found in the full scale HTR-PM with empirical correlations and non-dimensional ratios relating the HTR-PM and the scaled OSU HTTF. Computational fluid dynamics (CFD) are then used to produce computer simulations that show the scaling was satisfactorily performed. Title: Scaling of the Chinese HTR-PM Reactor Design for Licensing and Testing at the Oregon State University High Temperature Test Facility Author: Cox, Jordan (Jordan Tracy) The United States (US) Department of Energy (DOE) has identified the pebble-bed reactor as a high priority for US research with the end goal of licensing a pebble-bed reactor (PBR) for operation in the United States. Before this can be accomplished significant research must be done regarding the safety of the pebble-bed reactor. Of high interest is obtaining a better understanding of pebble-scale heat transfer and fluid flow within the PBR core. This thesis examines the ability of a hypothetical re-configured Oregon State University (OSU) High Temperature Test Facility (HTTF) to model the local phenomenon of the Chinese modular PBR (HTR-PM). Scaling analysis is used to quantify distortions that would occur between the HTR-PM and the scaled OSU HTTF. A one-fourth scaled test facility in height, core diameter, and pebble size is proposed. The scaling then demonstrates that this facility could model heat transfer, temperature profiles, and fluid forces found in the full scale HTR-PM with empirical correlations and non-dimensional ratios relating the HTR-PM and the scaled OSU HTTF. Computational fluid dynamics (CFD) are then used to produce computer simulations that show the scaling was satisfactorily performed. Close

• 18. [Article] Fully developed laminar natural convection in a vertical parallel-plate duct with constant wall heat flux

  The problem of heat transfer due to free convection in a channel formed by two parallel, isoflux, vertical plates is of considerable importance in electronic cooling applications, thermosiphons, the optimum ...

  Citation × Citation Citation Abstract Copy Title: Fully developed laminar natural convection in a vertical parallel-plate duct with constant wall heat flux Author: Aktan, Gülçin The problem of heat transfer due to free convection in a channel formed by two parallel, isoflux, vertical plates is of considerable importance in electronic cooling applications, thermosiphons, the optimum spacing of plates or components, industrial stacks, heat exchangers, nuclear power plants and combustion involving vertical walls. Although in each implementation other physical considerations are necessary, fully developed flow with symmetric isoflux boundary condition offers a fundamental heat transfer problem. Thus, here, the fully developed laminar natural convective flow of a viscous fluid in a channel formed by heated infinitely long vertical plates is investigated. Using boundary layer approximations, the basic governing equations of continuity, momentum and energy are combined into a single equation and solved analytically for a symmetric uniform heat flux boundary condition to find the velocity and temperature profiles and heat transfer coefficients for the flow. The closed-form solutions that are presented are strightforward and simple compared to previous solutions existing in the literature. For Rayleigh numbers sufficiently small to ensure a fully developed flow, it is found that the local Nusselt number based on local wall to bulk temperature difference is 4.118. Furthermore the pressure and mass flow rates for this particular geometry are also investigated. Title: Fully developed laminar natural convection in a vertical parallel-plate duct with constant wall heat flux Author: Aktan, Gülçin The problem of heat transfer due to free convection in a channel formed by two parallel, isoflux, vertical plates is of considerable importance in electronic cooling applications, thermosiphons, the optimum spacing of plates or components, industrial stacks, heat exchangers, nuclear power plants and combustion involving vertical walls. Although in each implementation other physical considerations are necessary, fully developed flow with symmetric isoflux boundary condition offers a fundamental heat transfer problem. Thus, here, the fully developed laminar natural convective flow of a viscous fluid in a channel formed by heated infinitely long vertical plates is investigated. Using boundary layer approximations, the basic governing equations of continuity, momentum and energy are combined into a single equation and solved analytically for a symmetric uniform heat flux boundary condition to find the velocity and temperature profiles and heat transfer coefficients for the flow. The closed-form solutions that are presented are strightforward and simple compared to previous solutions existing in the literature. For Rayleigh numbers sufficiently small to ensure a fully developed flow, it is found that the local Nusselt number based on local wall to bulk temperature difference is 4.118. Furthermore the pressure and mass flow rates for this particular geometry are also investigated. Close

• 19. [Article] An evaluation of finite difference methods for calculating heat transfer in fuel pins with eccentrically placed pellets

  In fuel pin fabrication, there is no assurance that a fuel pellet will be loaded concentrically. Therefore, azimuthal variations exist in the temperature field giving rise to asymmetry in the neutron flux ...

  Citation × Citation Citation Abstract Copy Title: An evaluation of finite difference methods for calculating heat transfer in fuel pins with eccentrically placed pellets Author: McNair, Gary W. In fuel pin fabrication, there is no assurance that a fuel pellet will be loaded concentrically. Therefore, azimuthal variations exist in the temperature field giving rise to asymmetry in the neutron flux distribution and pin stresses. Calculations must be made to determine the two dimensional temperature profile which may then be used to evaluate the resulting fuel pellet and cladding stresses and deformations. It is most convenient, in these type calculations, to utilize an existing general purpose finite difference code. However, these codes can only treat concentric regions. Two general approaches have been used to treat the problem. The first is to approximate the outer boundary by a ratchet. This results in an increase in the number of radial node regions required and a subsequent loss of economy. The second approach utilizes concentric regions and defines a variable conductivity within the gas gap to account for the eccentric condition. This reduces the number of radial node regions and results in savings in both computation time and core space. The purpose of this paper is to evaluate these two approaches for power reactor fuel pin calculations and extend the methodology to general eccentric calculations. Title: An evaluation of finite difference methods for calculating heat transfer in fuel pins with eccentrically placed pellets Author: McNair, Gary W. In fuel pin fabrication, there is no assurance that a fuel pellet will be loaded concentrically. Therefore, azimuthal variations exist in the temperature field giving rise to asymmetry in the neutron flux distribution and pin stresses. Calculations must be made to determine the two dimensional temperature profile which may then be used to evaluate the resulting fuel pellet and cladding stresses and deformations. It is most convenient, in these type calculations, to utilize an existing general purpose finite difference code. However, these codes can only treat concentric regions. Two general approaches have been used to treat the problem. The first is to approximate the outer boundary by a ratchet. This results in an increase in the number of radial node regions required and a subsequent loss of economy. The second approach utilizes concentric regions and defines a variable conductivity within the gas gap to account for the eccentric condition. This reduces the number of radial node regions and results in savings in both computation time and core space. The purpose of this paper is to evaluate these two approaches for power reactor fuel pin calculations and extend the methodology to general eccentric calculations. Close

• 20. [Article] An experimental investigation of natural convection heat transfer from vertical flat plates in mercury

  Heat transfer from a vertical flat plate in an infinite pool of mercury was investigated. Velocity profiles were measured with a hot-film anemometer and simultaneous temperature profiles measured with ...

  Citation × Citation Citation Abstract Copy Title: An experimental investigation of natural convection heat transfer from vertical flat plates in mercury Author: White, Donald Henry Heat transfer from a vertical flat plate in an infinite pool of mercury was investigated. Velocity profiles were measured with a hot-film anemometer and simultaneous temperature profiles measured with thermocouples in this low Prandtl number liquid metal. Constant heat flux plates at Grashof numbers of 9 x 10⁸ and 4 x 10⁷ were investigated. Pseudo-constant temperature plates at Grashof numbers of 8 x 10⁷ and 2 x 10⁷ were investigated. The velocity profiles, the first known natural convection experimental profiles reported for liquid metals, were found to be a function of both plate position and Grashof number. This relationship was predicted by available perturbation solutions for the flat plate in an infinite, low Prandtl number fluid, but not by the similarity or integral solutions. Indications are that the best analytical solutions do a poor job of predicting profiles and that natural convection heat transfer rates in liquid metals are higher than originally believed. The use of a hot-film anemometer to measure low velocities in mercury is possible, but the existence of a thermo-barrier film causes serious experimental problems which have been only partially solved. Title: An experimental investigation of natural convection heat transfer from vertical flat plates in mercury Author: White, Donald Henry Heat transfer from a vertical flat plate in an infinite pool of mercury was investigated. Velocity profiles were measured with a hot-film anemometer and simultaneous temperature profiles measured with thermocouples in this low Prandtl number liquid metal. Constant heat flux plates at Grashof numbers of 9 x 10⁸ and 4 x 10⁷ were investigated. Pseudo-constant temperature plates at Grashof numbers of 8 x 10⁷ and 2 x 10⁷ were investigated. The velocity profiles, the first known natural convection experimental profiles reported for liquid metals, were found to be a function of both plate position and Grashof number. This relationship was predicted by available perturbation solutions for the flat plate in an infinite, low Prandtl number fluid, but not by the similarity or integral solutions. Indications are that the best analytical solutions do a poor job of predicting profiles and that natural convection heat transfer rates in liquid metals are higher than originally believed. The use of a hot-film anemometer to measure low velocities in mercury is possible, but the existence of a thermo-barrier film causes serious experimental problems which have been only partially solved. Close