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02382 Investigations on post-dryout heat transfer in bilaterally heated annular channels
14 Fuel science and technology (fundamental science, analysis, instrumentation) 06102375 Determination of boron in Zr-Nb alloys by glow discharge quadrupole mass spectrometry Shekhar, R. et al. Journal qfNuelear 3laterials, 2005, 340, (2 3), 284 290. Direct determination of boron in Zr-2.5%Nb, Zr-1%Nb alloys and zirconium metals which are extensively used as structural materials in nuclear reactors has been carried out by glow discharge quadrupole mass spectrometer (GD-QMS). Relative sensitive factor (RSF) values for boron were determined using different solid standard reference materials (Zircaloy and steel). A comparison of the GD-QMS results obtained using these RSF values, with DC-Arc-AES (direct current arc atomic emission spectrometry)/certified values showed reasonably good agreement in all the Zr-based materials analysed for boron in the range of 0.1-7 mg kg -~. Quantitation of boron in Zr matrix is possible even with a steel standard when certified for Zr and B. Internal precision (intra-sample precision) was found to be typically ±4% RSD (relative standard deviation) and the inter-sample precision was ±10% RSD for boron at 0.1 mg kg i levels. The overall accuracy of the procedure was found to be ±8% at ~0.5 mg kg i levels of boron using Zircaloy and steel standards. Under optimized experimental conditions the detection limit for boron was found to be ±13 pg kg i.
06/02376 Effects of void uncertainties on the void reactivity coefficient and pin power distributions for a 10 × 10 BWR assembly Jatuff, F. et al. Annals of Nuclear Energy, 2006, 33, (2), 119 125. An important source of uncertainty in boiling water reactor physics is associated with the precise characterization of the moderation properties of the coolant and by-pass regions, with significant impact on reactor physics parameters such as the lattice neutron multiplication, the neutron migration area and the pin-by-pin power distribution. In this paper, the effects of certain relevant void-fraction uncertainties on reactor physics parameters have been studied for a boiling water reactor (BWR) assembly of the type Westinghouse SVEA-96 using CASMO-4, HELIOS/PRESTO-2 and MCNP4C. The SVEA-96 geometry is characterized by the sub-division of the assembly into four different sub-bundles, by means of an inner by-pass with a cruciform shape. The study has covered: (a) the effects of different cross-section data libraries on the void coefficient of reactivity, for a wide range of void fractions; (b) the consideration of a water film inside the subbundle walls, and (c) the impact of partly inserted absorber blades producing very different void fractions in different sub-bundles.
06•02377 Exergy-based ecological optimization for a generalized irreversible Carnot refrigerator Zhu, X. et al. Journal of the Energy Institute, 2006, 79, (1), 42 46. The optimal exergy-based ecological performance of an irreversible Carnot refrigerator with the losses of heat-resistance, heat leak and internal irreversibility, in which heat transfer between the working fluid and the heat reservoirs obeys a generalized heat transfer law QA(Tn), is derived by considering an ecological optimization criterion as the objective function, which consists of maximizing a function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the refrigerator. Some special examples are discussed. Numerical examples are given to show the efl'ects of heat transfer law, heat leakage and internal irreversibility on the optimal performance of the generalized irreversible refrigerator. The results can provide some theoretical guidance for the design of practical refrigerators.
06/02378 Experimental and modelling study of the radiative curing of a polyester-based coating V6chot, L. et al. International Journal of Thernml Sciences, 2006, 45, (1), 86 93. This experimental investigation is structured to describe the thermal behaviour of a polyester + TGIC powder coating during infrared curing. The study hence correlates thermal modelling of the cure process and kinetics studies. First, the curing kinetics is determined using DSC experiments and modelling with the software Matlab. The results from this study are then used to study the infrared curing efficiency. Medium wave infrared leads to the fastest cure. Moreover, coupling the thermal modelling of the cure process and the kinetics has enabled us to develop a model predicting the evolution of the temperature and the degree of conversion, using the hypothesis that the paint film and the substrate are at the same temperature.
06•02379 Experimental and numerical simulations of turbulent ventilation in aircraft cabins Bosbach, J. et al. Energy, 2006, 31, (5), 694 705. Airflow in a generic airplane cabin has been investigated numerically by means of Reynolds averaged Navier-Stokes computations and experimentally by particle image velocimetry (PIV). High and low Reynolds number as well as two layer turbulence models were tested for their ability to describe turbulent velocity fields. Special attention was given to the flow of the incoming air jet along the luggage
compartment. Comparison with PIV measurements reveals that for reliable prediction of isothermal cabin flow, low Reynolds number turbulence models have to be used.
06102380 Heat transfers and pressure drops for porousring turbulators in a circular pipe Akansu, S. O. Applied Energy, 2006, 83, (3), 280-298. A numerical heat-transfer and pressure-drop analysis is presented for porous rings inserted in a pipe at a distance L apart. A constant heatflux is applied to the outer surface of the pipe. Numerical calculations are conducted with the Fluent 6.1.22 code, using the shear-stress transport (SST) k-w model. Air is the fluid. The heat-transfer increase is analysed for Reynolds numbers from 3 × 103 to 45 × 103. The porous-ring height is taken as H = 1 or 2 mm. The distance between two porous rings is 0.5D, D or 2D where D is the inside diameter of the pipe. An increase in LID caused a decrease in heat-transfer. High Nusselt numbers were obtained when HID and L/D ratios were 0.4 and 0.5, respectively, for a Reynold number of 45,000. The maximum Nusselt number occurred when L/D = 1 if HID is selected as 0.2.
06/02381 Influence of regeneration on the performance of a Brayton refrigeration-cycle working with an ideal Bose-gas Yang, Y. et al. Applied Energy, 2006, 83, (2), 99-112. A general regenerative model of the Brayton refrigeration-cycle working with an ideal Bose-gas is used to discuss the influence of both the quantum degeneracy and regeneration on the performance of the cycle. Expressions for some important parameters, such as the refrigeration load, work input, coefficient of performance and minimum pressure-ratio, of the Brayton refrigeration-cycle are derived analytically and used to generate the refrigeration load, work input, coefficient of performance, and relative refrigeration-load versus pressure ratio curves. Moreover, several special cases are discussed in detail. The results obtained here will be helpful to reveal the performance characteristics of the Bose-Brayton refrigeration-cycle, further understand the difference and connection between the classical and quantum Brayton refrigeration-cycles, and theoretically expound the importance of the regeneration application for the Brayton refrigeration-cycle.
06•02382 Investigations on post-dryout heat transfer in bilaterally heated annular channels Tian, W. X. et al. Annals of Nuclear Energy, 2006, 33, (2), 189 197. Post-dryout heat transfer in bilaterally heated vertical narrow annular channels with 1.0, 1.5 and 2.0 mm gap size has been experimentally investigated with deionized water under the condition of pressure ranging from 1.38 to 5.9 MPa and low mass flow rate from 42.9 to 150.2 kg/m2s. The experimental data was compared with well-known empirical correlations including Groeneveld, Mattson, etc., and none of them gave an ideal prediction. Theoretical investigations were also carried out on post-dryout heat transfer in annular channels. Based on analysis of heat exchange processes arising among the droplets, the vapour and two tube walls of annular channel, a non-equilibrium mechanistic heat transfer model was developed. Comparison indicated that the present model prediction showed a good agreement with the experimental data. Theoretical calculation result showed that the forced convective heat transfer between the heated wall and vapour dominate the overall heat transfer. The heat transfer caused by the droplets direct contact to the wall and the interracial convection/ evaporation of droplets in superheated vapours also had an indispensable contribution. The radiation heat transfer would be neglected because of its small contribution (less than 0.11%) to the total heat transfer.
06•02383 Kinetic analysis of non-isothermal thermogravimetric analyser results using a new method for the evaluation of the temperature integral and multi-heating rates Everson, R. C. et al. Fuel, 2006, 85, (3), 418-422. A technique using non-isothermal thermogravimetric analyser results was developed for the validation of reaction rate models together with associated parameters suitable for chemically controlled gas-solid reactions. The solution of the temperature integral which occurs in the calculation is achieved by numerical integration with respect to a dimensionless activation energy variable, y = E/RT, following a transformation of the temperature integral equation. The evaluation of the validity of the kinetic model and determination of all the constants is accomplished with a two-step regression procedure with experimental results from several thermogrammes with different linear heating rates. The technique was validated by comparing results obtained for the combustion of two coal-chars with corresponding isothermal results using a shrinking core model with a nth order surface reaction.
Fuel and Energy Abstracts September 2006
361
06/02376 Effects of void uncertainties on the void reactivity coefficient and pin power distributions for a 10 × 10 BWR assembly Jatuff, F. et al. Annals of Nuclear Energy, 2006, 33, (2), 119 125. An important source of uncertainty in boiling water reactor physics is associated with the precise characterization of the moderation properties of the coolant and by-pass regions, with significant impact on reactor physics parameters such as the lattice neutron multiplication, the neutron migration area and the pin-by-pin power distribution. In this paper, the effects of certain relevant void-fraction uncertainties on reactor physics parameters have been studied for a boiling water reactor (BWR) assembly of the type Westinghouse SVEA-96 using CASMO-4, HELIOS/PRESTO-2 and MCNP4C. The SVEA-96 geometry is characterized by the sub-division of the assembly into four different sub-bundles, by means of an inner by-pass with a cruciform shape. The study has covered: (a) the effects of different cross-section data libraries on the void coefficient of reactivity, for a wide range of void fractions; (b) the consideration of a water film inside the subbundle walls, and (c) the impact of partly inserted absorber blades producing very different void fractions in different sub-bundles.
06•02377 Exergy-based ecological optimization for a generalized irreversible Carnot refrigerator Zhu, X. et al. Journal of the Energy Institute, 2006, 79, (1), 42 46. The optimal exergy-based ecological performance of an irreversible Carnot refrigerator with the losses of heat-resistance, heat leak and internal irreversibility, in which heat transfer between the working fluid and the heat reservoirs obeys a generalized heat transfer law QA(Tn), is derived by considering an ecological optimization criterion as the objective function, which consists of maximizing a function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the refrigerator. Some special examples are discussed. Numerical examples are given to show the efl'ects of heat transfer law, heat leakage and internal irreversibility on the optimal performance of the generalized irreversible refrigerator. The results can provide some theoretical guidance for the design of practical refrigerators.
06/02378 Experimental and modelling study of the radiative curing of a polyester-based coating V6chot, L. et al. International Journal of Thernml Sciences, 2006, 45, (1), 86 93. This experimental investigation is structured to describe the thermal behaviour of a polyester + TGIC powder coating during infrared curing. The study hence correlates thermal modelling of the cure process and kinetics studies. First, the curing kinetics is determined using DSC experiments and modelling with the software Matlab. The results from this study are then used to study the infrared curing efficiency. Medium wave infrared leads to the fastest cure. Moreover, coupling the thermal modelling of the cure process and the kinetics has enabled us to develop a model predicting the evolution of the temperature and the degree of conversion, using the hypothesis that the paint film and the substrate are at the same temperature.
06•02379 Experimental and numerical simulations of turbulent ventilation in aircraft cabins Bosbach, J. et al. Energy, 2006, 31, (5), 694 705. Airflow in a generic airplane cabin has been investigated numerically by means of Reynolds averaged Navier-Stokes computations and experimentally by particle image velocimetry (PIV). High and low Reynolds number as well as two layer turbulence models were tested for their ability to describe turbulent velocity fields. Special attention was given to the flow of the incoming air jet along the luggage
compartment. Comparison with PIV measurements reveals that for reliable prediction of isothermal cabin flow, low Reynolds number turbulence models have to be used.
06102380 Heat transfers and pressure drops for porousring turbulators in a circular pipe Akansu, S. O. Applied Energy, 2006, 83, (3), 280-298. A numerical heat-transfer and pressure-drop analysis is presented for porous rings inserted in a pipe at a distance L apart. A constant heatflux is applied to the outer surface of the pipe. Numerical calculations are conducted with the Fluent 6.1.22 code, using the shear-stress transport (SST) k-w model. Air is the fluid. The heat-transfer increase is analysed for Reynolds numbers from 3 × 103 to 45 × 103. The porous-ring height is taken as H = 1 or 2 mm. The distance between two porous rings is 0.5D, D or 2D where D is the inside diameter of the pipe. An increase in LID caused a decrease in heat-transfer. High Nusselt numbers were obtained when HID and L/D ratios were 0.4 and 0.5, respectively, for a Reynold number of 45,000. The maximum Nusselt number occurred when L/D = 1 if HID is selected as 0.2.
06/02381 Influence of regeneration on the performance of a Brayton refrigeration-cycle working with an ideal Bose-gas Yang, Y. et al. Applied Energy, 2006, 83, (2), 99-112. A general regenerative model of the Brayton refrigeration-cycle working with an ideal Bose-gas is used to discuss the influence of both the quantum degeneracy and regeneration on the performance of the cycle. Expressions for some important parameters, such as the refrigeration load, work input, coefficient of performance and minimum pressure-ratio, of the Brayton refrigeration-cycle are derived analytically and used to generate the refrigeration load, work input, coefficient of performance, and relative refrigeration-load versus pressure ratio curves. Moreover, several special cases are discussed in detail. The results obtained here will be helpful to reveal the performance characteristics of the Bose-Brayton refrigeration-cycle, further understand the difference and connection between the classical and quantum Brayton refrigeration-cycles, and theoretically expound the importance of the regeneration application for the Brayton refrigeration-cycle.
06•02382 Investigations on post-dryout heat transfer in bilaterally heated annular channels Tian, W. X. et al. Annals of Nuclear Energy, 2006, 33, (2), 189 197. Post-dryout heat transfer in bilaterally heated vertical narrow annular channels with 1.0, 1.5 and 2.0 mm gap size has been experimentally investigated with deionized water under the condition of pressure ranging from 1.38 to 5.9 MPa and low mass flow rate from 42.9 to 150.2 kg/m2s. The experimental data was compared with well-known empirical correlations including Groeneveld, Mattson, etc., and none of them gave an ideal prediction. Theoretical investigations were also carried out on post-dryout heat transfer in annular channels. Based on analysis of heat exchange processes arising among the droplets, the vapour and two tube walls of annular channel, a non-equilibrium mechanistic heat transfer model was developed. Comparison indicated that the present model prediction showed a good agreement with the experimental data. Theoretical calculation result showed that the forced convective heat transfer between the heated wall and vapour dominate the overall heat transfer. The heat transfer caused by the droplets direct contact to the wall and the interracial convection/ evaporation of droplets in superheated vapours also had an indispensable contribution. The radiation heat transfer would be neglected because of its small contribution (less than 0.11%) to the total heat transfer.
06•02383 Kinetic analysis of non-isothermal thermogravimetric analyser results using a new method for the evaluation of the temperature integral and multi-heating rates Everson, R. C. et al. Fuel, 2006, 85, (3), 418-422. A technique using non-isothermal thermogravimetric analyser results was developed for the validation of reaction rate models together with associated parameters suitable for chemically controlled gas-solid reactions. The solution of the temperature integral which occurs in the calculation is achieved by numerical integration with respect to a dimensionless activation energy variable, y = E/RT, following a transformation of the temperature integral equation. The evaluation of the validity of the kinetic model and determination of all the constants is accomplished with a two-step regression procedure with experimental results from several thermogrammes with different linear heating rates. The technique was validated by comparing results obtained for the combustion of two coal-chars with corresponding isothermal results using a shrinking core model with a nth order surface reaction.
Fuel and Energy Abstracts September 2006
361