The goal of next generation reactors is to increase energy efficiency in the production of electr... more The goal of next generation reactors is to increase energy efficiency in the production of electricity and provide high-temperature heat for industrial processes. The efficient transfer of energy for industrial applications depends on the ability to incorporate effective heat exchangers between the nuclear heat transport system and the industrial process. The need for efficiency, compactness, and safety challenge the boundaries of existing heat exchanger technology. Various studies have been performed in attempts to update the secondary heat exchanger that is downstream of the primary heat exchanger, mostly because its performance is strongly tied to the ability to employ more efficient industrial processes. Modern compact heat exchangers can provide high compactness, a measure of the ratio of surface area-to-volume of a heat exchange. The microchannel heat exchanger studied here is a plate-type, robust heat exchanger that combines compact-ness, low pressure drop, high effectiveness, and the ability to operate with a very large pressure differential between hot and cold sides. The plates are etched and thereafter joined by diffusion welding, resulting in extremely strong all-metal heat exchanger cores. After bonding, any number of core blocks can be welded together to provide the required flow capacity. This study explores the microchannel heat exchanger and draws conclusions about diffusion welding/bonding for joining heat exchanger plates, with both experimental and computational modeling, along with existing challenges and gaps. Also, presented is a thermal design method for determining overall design specifications for a microchannel printed circuit heat exchanger for both supercritical (24 MPa) and subcritical (17 MPa) Rankine power cycles.
A general asymmetric yield function is proposed with dependence on the stress invariants for pres... more A general asymmetric yield function is proposed with dependence on the stress invariants for pressure sensitive metals. The pressure sensitivity of the proposed yield function is consistent with the experimental result of Spitzig and Richmond (1984) for steel and aluminum alloys while the asymmetry of the third invariant is preserved to model strength differential (SD) effect of pressure insensitive materials. The proposed yield function is transformed in the space of the stress triaxaility, the von Mises stress and the normalized invariant to theoretically investigate the possible reason of the SD effect. The proposed plasticity model is further extended to characterize the anisotropic behavior of metals both in tension and compression. The extension of the yield function is realized by introducing two distinct fourth-order linear transformation tensors of the stress tensor for the second and third invariants, respectively. The extended yield function reasonably models the evolution of yield surfaces for a zirconium clock-rolled plate during in-plane and through-thickness compression reported by Plunkett et al. (2007). The extended yield function is also applied to describe the orthotropic behavior of a face-centered cubic metal of AA 2008-T4 and two hexagonal close-packed metals of high-purity a-titanium and AZ31 magnesium alloy. The orthotropic behavior predicted by the generalized model is compared with experimental results of these metals. The comparison validates that the proposed yield function provides sufficient predictability on SD effect and anisotropic behavior both in tension and compression. When it is necessary to consider r-value anisotropy, the proposed function is efficient to be used with non-associated flow plasticity by introducing a separate plastic potential for the consideration of r-values as shown in Stoughton and Yoon (2004, 2009).
The present invention consists of an Al-Ni-Mn based alloy for die casting, squeeze casting, perma... more The present invention consists of an Al-Ni-Mn based alloy for die casting, squeeze casting, permanent mold casting, sand casting and/or semi-solid metal forming. Preferred embodiments of this alloy include the following compositional additions, all in weight percent: about 0.5-6% Ni, about 1-3% Mn, less than about 1% Fe, less than about 1% Si, less than about 0.3% Ti, and less than about 0.06% B, the balance Al, incidental elements and impurities. On a more preferred basis, this alloy composition consists essentially of about 3.5-4.5% Ni, about 1.5-2.5% Mn, less than about 0.1% Fe, less than about 0.1% Si, less than about 0.15% Ti, and less than about 0.03% B, the balance A1 and incidentals.
Thermally stable transitional alumina retaining high specific surface area after calcination at 1... more Thermally stable transitional alumina retaining high specific surface area after calcination at 1000 C, suitable for the use as catalysts or catalytic supports are produced by treating an aqueous solution containing Al+3 and optionally a doping amount of La+3 (e.g., 0.3 mol.%) with an anion exchange rasin to give a stable hydroxide sol followed by freeze drying of the sol and further thermal dehydration. The resultant stabilized transitional alumina retains high specific surface area at 1000 C, and additionally stabilization is achieved with a very low level of added La.
This technical evaluation (TEV) has been prepared to evaluate the possibility of the formation of... more This technical evaluation (TEV) has been prepared to evaluate the possibility of the formation of explosive and/or highly toxic substances during molten salt pyrolysis of oil residue. It particular, it addresses the possibility of a self-sustained chemical reaction developing in the reactor due to the potential formation of the sodium vapor, highly energetic nitrogen-bearing compounds (e.g., azides), and the influence of the trace amounts of heavy metals (inevitably present in any oil residue) upon these chemical reactions. For chemistry evaluation, standard thermodynamic calculations were conducted using the software ThermoCalc Software AB (Stockholm, Sweden) along with the commercial thermodynamic databases from ThermoCalc Software AB and the ThermoTech Inc. (University of Cambridge, UK). These calculations were validated by comparing the computed values of the Gibbs thermodynamic potentials to the existing reliable experimental data for a number of chemical processes in different...
The goal of next generation reactors is to increase energy efficiency in the production of electr... more The goal of next generation reactors is to increase energy efficiency in the production of electricity and provide high-temperature heat for industrial processes. The efficient transfer of energy for industrial applications depends on the ability to incorporate effective heat exchangers between the nuclear heat transport system and the industrial process. The need for efficiency, compactness, and safety challenge the boundaries of existing heat exchanger technology. Various studies have been performed in attempts to update the secondary heat exchanger that is downstream of the primary heat exchanger, mostly because its performance is strongly tied to the ability to employ more efficient industrial processes. Modern compact heat exchangers can provide high compactness, a measure of the ratio of surface area-to-volume of a heat exchange. The microchannel heat exchanger studied here is a plate-type, robust heat exchanger that combines compact-ness, low pressure drop, high effectiveness, and the ability to operate with a very large pressure differential between hot and cold sides. The plates are etched and thereafter joined by diffusion welding, resulting in extremely strong all-metal heat exchanger cores. After bonding, any number of core blocks can be welded together to provide the required flow capacity. This study explores the microchannel heat exchanger and draws conclusions about diffusion welding/bonding for joining heat exchanger plates, with both experimental and computational modeling, along with existing challenges and gaps. Also, presented is a thermal design method for determining overall design specifications for a microchannel printed circuit heat exchanger for both supercritical (24 MPa) and subcritical (17 MPa) Rankine power cycles.
A general asymmetric yield function is proposed with dependence on the stress invariants for pres... more A general asymmetric yield function is proposed with dependence on the stress invariants for pressure sensitive metals. The pressure sensitivity of the proposed yield function is consistent with the experimental result of Spitzig and Richmond (1984) for steel and aluminum alloys while the asymmetry of the third invariant is preserved to model strength differential (SD) effect of pressure insensitive materials. The proposed yield function is transformed in the space of the stress triaxaility, the von Mises stress and the normalized invariant to theoretically investigate the possible reason of the SD effect. The proposed plasticity model is further extended to characterize the anisotropic behavior of metals both in tension and compression. The extension of the yield function is realized by introducing two distinct fourth-order linear transformation tensors of the stress tensor for the second and third invariants, respectively. The extended yield function reasonably models the evolution of yield surfaces for a zirconium clock-rolled plate during in-plane and through-thickness compression reported by Plunkett et al. (2007). The extended yield function is also applied to describe the orthotropic behavior of a face-centered cubic metal of AA 2008-T4 and two hexagonal close-packed metals of high-purity a-titanium and AZ31 magnesium alloy. The orthotropic behavior predicted by the generalized model is compared with experimental results of these metals. The comparison validates that the proposed yield function provides sufficient predictability on SD effect and anisotropic behavior both in tension and compression. When it is necessary to consider r-value anisotropy, the proposed function is efficient to be used with non-associated flow plasticity by introducing a separate plastic potential for the consideration of r-values as shown in Stoughton and Yoon (2004, 2009).
The present invention consists of an Al-Ni-Mn based alloy for die casting, squeeze casting, perma... more The present invention consists of an Al-Ni-Mn based alloy for die casting, squeeze casting, permanent mold casting, sand casting and/or semi-solid metal forming. Preferred embodiments of this alloy include the following compositional additions, all in weight percent: about 0.5-6% Ni, about 1-3% Mn, less than about 1% Fe, less than about 1% Si, less than about 0.3% Ti, and less than about 0.06% B, the balance Al, incidental elements and impurities. On a more preferred basis, this alloy composition consists essentially of about 3.5-4.5% Ni, about 1.5-2.5% Mn, less than about 0.1% Fe, less than about 0.1% Si, less than about 0.15% Ti, and less than about 0.03% B, the balance A1 and incidentals.
Thermally stable transitional alumina retaining high specific surface area after calcination at 1... more Thermally stable transitional alumina retaining high specific surface area after calcination at 1000 C, suitable for the use as catalysts or catalytic supports are produced by treating an aqueous solution containing Al+3 and optionally a doping amount of La+3 (e.g., 0.3 mol.%) with an anion exchange rasin to give a stable hydroxide sol followed by freeze drying of the sol and further thermal dehydration. The resultant stabilized transitional alumina retains high specific surface area at 1000 C, and additionally stabilization is achieved with a very low level of added La.
This technical evaluation (TEV) has been prepared to evaluate the possibility of the formation of... more This technical evaluation (TEV) has been prepared to evaluate the possibility of the formation of explosive and/or highly toxic substances during molten salt pyrolysis of oil residue. It particular, it addresses the possibility of a self-sustained chemical reaction developing in the reactor due to the potential formation of the sodium vapor, highly energetic nitrogen-bearing compounds (e.g., azides), and the influence of the trace amounts of heavy metals (inevitably present in any oil residue) upon these chemical reactions. For chemistry evaluation, standard thermodynamic calculations were conducted using the software ThermoCalc Software AB (Stockholm, Sweden) along with the commercial thermodynamic databases from ThermoCalc Software AB and the ThermoTech Inc. (University of Cambridge, UK). These calculations were validated by comparing the computed values of the Gibbs thermodynamic potentials to the existing reliable experimental data for a number of chemical processes in different...
The goal of next generation reactors is to increase energy efficiency in the production of electr... more The goal of next generation reactors is to increase energy efficiency in the production of electricity and provide high-temperature heat for industrial processes. The efficient transfer of energy for industrial applications depends on the ability to incorporate effective heat exchangers between the nuclear heat transport system and the industrial process. The need for efficiency, compactness, and safety challenge the boundaries of existing heat exchanger technology. Various studies have been performed in attempts to update the secondary heat exchanger that is downstream of the primary heat exchanger, mostly because its performance is strongly tied to the ability to employ more efficient industrial processes. Modern compact heat exchangers can provide high compactness, a measure of the ratio of surface area-to-volume of a heat exchange. The microchannel heat exchanger studied here is a plate-type, robust heat exchanger that combines compact-ness, low pressure drop, high effectiveness, and the ability to operate with a very large pressure differential between hot and cold sides. The plates are etched and thereafter joined by diffusion welding, resulting in extremely strong all-metal heat exchanger cores. After bonding, any number of core blocks can be welded together to provide the required flow capacity. This study explores the microchannel heat exchanger and draws conclusions about diffusion welding/bonding for joining heat exchanger plates, with both experimental and computational modeling, along with existing challenges and gaps. Also, presented is a thermal design method for determining overall design specifications for a microchannel printed circuit heat exchanger for both supercritical (24 MPa) and subcritical (17 MPa) Rankine power cycles.
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Papers by Michael V Glazoff