- Email: [email protected]
01891 Transmissive diamond photocathodes
14 Fuel science and technology (fundamental science, analysis, instrumentation) considered. The system reliability maximization subject to performance and cost constraints is well known as reliability optimization problem. In reality, the system has a range of performance levels, in this case a multi-state system (MSS) reliability is defined as the ability to maintain a specified performance level. A procedure, which determines the maximal reliability of series-parallel electrical power system topology is proposed. In this procedure, electrical system devices are chosen among a list of available devices on the market. Electrical devices are characterized by their reliability, performance and cost. To evaluate the systems reliability, a universal moment generating function (UMGF) approach is used by the ant colony algorithm (ACA) to determine the optimal electrical power network topology. A computer program has been developed to implement the UMGF technique combined with the ACA. An illustrative example is treated at the end of this work.
06/01884 Reliable datasets for lighting programs validation - benchmark results Maamari, F. et al. Solar Energy, 2005, 79, (2), 213-215. A set of simple test cases have been defined, within the activities of the CIE technical committee 3.33 and Subtask C of the IEA S H e Task 31, based on analytical or experimental references, with the objective of assessing lighting computer programs. The present paper aims to show the applicability and the usefulness of these test cases through the analyses of a conducted set of benchmarks. It is shown that the use of the CIE test cases allows the verification of the level of accuracy of the tested programs with respect to the lighting physical laws that are highlighted separately within the different test cases. The comparison of the results of the different tested programs shows also that a program with a high accuracy in respect to a given aspect of lighting simulation is not necessarily accurate in simulating other aspects, which proves the usefulness of the CIE test cases in identifying the domain of applicability of a tested program.
06/01885 Single thermal zone balance solved by Transfer Function Method Beccali, G. et al. Energy and Buildings, 2005, 37, (12), 1268-1277. The authors present an algorithm that uses the Z-transform operator to face the problem of heat transmission in a single thermal zone composed by multi-layered walls. The method is very flexible and could be adopted to calculate the transfer function coefficients able to simulate the thermal behaviour of a room in free floating. Knowing the transfer function coefficients, it is possible to simulate the dynamic profile of each inner surfaces temperature and furthermore of the inner air temperature. The proposed algorithm is fully described granting maximum clarity. The explicitness of all steps of the calculus make possible the definition of a method that is able to vary all of the calculus parameters such as sampling g period, number of roots, number of poles or number of coefficients. To assess the reliability of the algorithm, a comparison was carried out between simulation data obtained from the method, from Fourier steady-state algorithm and those obtained from TRNSYS.
06/01886 Spectrogram analysis of the time-frequency characteristics of ocean wind waves Guedes Soares, C. and Cherneva, Z. Ocean Engineering, 2005, 32, (1415), 1643-1663. The spectrogram based on the short-time Fourier transform is proposed as a tool to study the time frequency evolution of the properties of ocean wind waves. After defining the method to determine the spectrogram of wind waves an example of application is given by analysing the time series from three sea states concerning a swell, a wind sea and a mixed sea situation. It is shown how the power spectral density function changes with time and its nature when a wave group exists. The result suggests that the energy transfer from high to low frequencies does not occur continuously but in localized periods, exactly when the wave groups occur.
06/01887 Studies on simultaneous energy and water minimisation - Part I: systems with no water re-use Savulescu, L. et al. Chemical Engineering Science, 2005, 60, (12), 32793290. This paper addresses the simultaneous management of energy and water. A new systematic methodology has been developed for targeting and design that simultaneously minimizes the requirements of energy and water. Using this new approach, the design of a water system for maximum energy recovery can be achieved, taking into account the mixing opportunities offered by water networks, while maintaining the water quality to processes in terms of contamination. Direct and indirect energy recovery are analysed and a strategy developed to decrease the number of heat transfer units based on the generation of separate systems and non-isothermal stream mixing. Initially, the analysis is restricted to no water re-use.
06/01888 Studies on simultaneous energy and water minimisation - Part Ih systems with maximum re-use of water Savulescu, L. et al. Chemical Engineering Science, 2005, 60, (12), 3291 3308. A new systematic design methodology has been developed for the simultaneous management of energy and water systems that also feature maximum re-use of water. A two-dimensional grid diagram is proposed to exploit different options within water systems and also enable reduced complexity of the energy and water network. Isothermal and non-isothermal stream mixing between water streams are introduced to create separate systems between hot and cold water streams in the energy composite curves and provide a design basis for a better structure with fewer units for the heat exchanger network. In addition to allowing re-use of water, issues about heat losses inside unit operations have also been incorporated in the simultaneous management of water and energy.
06/01889 Surface configuration relevance in the overall thermal resistance of a wall Pires, L. et al. Energy and Buildings, 2005, 37, (10), 1068-1074. In the present work studies of experimental nature were made to evaluate the importance of the wall surface configuration related to its overall thermal resistance. A parameter with major importance in the value of such resistance is the convection heat transfer coefficient. In this way, several different surfaces were built and the correspondent convection coefficient was determined for natural convection conditions. As a reference for the comparative study a smooth surface has also been constructed. The value of the convection coefficient for each surface was obtained with the help of an infrared thermography system. The obtained results show a reasonable reduction in the smooth surface convection coefficient, which leads to an increase in overall thermal resistance. Therefore, if the objective is to increase the heat transfer rate between a surface and its neighbours there should be used roughness surfaces.
06/01890 Thermoacoustic instabilities: should the Rayleigh criterion be extended to include entropy changes? Nicoud, F. and Poinsot, T. Combustion and Flame, 2005, 142, (1-2), 153-159. The Rayleigh criterion (which measures the correlation between pressure and heat release) is the standard tool used to investigate and predict combustion instabilities in both experimental and numerical studies. However, the Rayleigh term is just one of the terms appearing in the acoustic energy equation. The recent development of large eddy simulations for combustion chambers allows complete closure of the budget and analysis of all terms in this equation. This task leads to unexpected difficulties and requires some basic work, as multiple definitions of the energy of fluctuations in a reacting compressible flow can be derived. The objective of this article is to revisit the theoretical derivations of the fluctuation energy equations. Two forms of energy are defined: The first is the classic acoustic energy (AE) introduced by various authors. The second is the fluctuation energy (FE) presented in an earlier study by B.T. Chu. Both equations are rederived in a compact manner starting from full nonlinear forms. It is shown that the classic Rayleigh criterion naturally appears as the source term of the AE equation, while the FE form leads to a different criterion stating that temperature and heat release must be in phase for the instability to be fed by the flame/acoustics coupling. The FE form also integrates the fluctuations of three variables (pressure, velocity, entropy), while the AE form uses only pressure and velocity perturbations. It is shown that only the FE form should be used in flames, in contradiction to many current studies performed for combustion instabilities.
06/01891
Transmissive diamond photocathodes
Foord, J. S. et al. Carbon, 2005, 43, (9), 2106 2111. The first studies are reported on the characteristics of ultra-violet transmissive mode, chemical vapour deposition (CVD) diamond photocathodes, in which photoelectrons are emitted from a diamond membrane via the opposite interface from that of the incident radiation. For membranes in the thickness range 5-40 ~tm, the transmissive photoyield at threshold wavelengths is shown to be less but comparable to that measured for reflective, thick film diamond photocathodes. The characteristics are found to be insensitive to the phase purity of differing diamond membranes used, but are very dependent on whether the growth or substrate interfaces of the diamond membrane face the incident UV radiation. The factors influencing the characteristics observed are discussed.
06/01892 Two-dimensional C5G7 MOX fuel assembly benchmark calculations using the FEM-PN code EVENT Keller, S. E. and De Oliveira, C. R. E. Progress in Nuclear Energy, 2004, 45, (2-4), 255-263.
Fuel and Energy Abstracts
July 2006
285
06/01884 Reliable datasets for lighting programs validation - benchmark results Maamari, F. et al. Solar Energy, 2005, 79, (2), 213-215. A set of simple test cases have been defined, within the activities of the CIE technical committee 3.33 and Subtask C of the IEA S H e Task 31, based on analytical or experimental references, with the objective of assessing lighting computer programs. The present paper aims to show the applicability and the usefulness of these test cases through the analyses of a conducted set of benchmarks. It is shown that the use of the CIE test cases allows the verification of the level of accuracy of the tested programs with respect to the lighting physical laws that are highlighted separately within the different test cases. The comparison of the results of the different tested programs shows also that a program with a high accuracy in respect to a given aspect of lighting simulation is not necessarily accurate in simulating other aspects, which proves the usefulness of the CIE test cases in identifying the domain of applicability of a tested program.
06/01885 Single thermal zone balance solved by Transfer Function Method Beccali, G. et al. Energy and Buildings, 2005, 37, (12), 1268-1277. The authors present an algorithm that uses the Z-transform operator to face the problem of heat transmission in a single thermal zone composed by multi-layered walls. The method is very flexible and could be adopted to calculate the transfer function coefficients able to simulate the thermal behaviour of a room in free floating. Knowing the transfer function coefficients, it is possible to simulate the dynamic profile of each inner surfaces temperature and furthermore of the inner air temperature. The proposed algorithm is fully described granting maximum clarity. The explicitness of all steps of the calculus make possible the definition of a method that is able to vary all of the calculus parameters such as sampling g period, number of roots, number of poles or number of coefficients. To assess the reliability of the algorithm, a comparison was carried out between simulation data obtained from the method, from Fourier steady-state algorithm and those obtained from TRNSYS.
06/01886 Spectrogram analysis of the time-frequency characteristics of ocean wind waves Guedes Soares, C. and Cherneva, Z. Ocean Engineering, 2005, 32, (1415), 1643-1663. The spectrogram based on the short-time Fourier transform is proposed as a tool to study the time frequency evolution of the properties of ocean wind waves. After defining the method to determine the spectrogram of wind waves an example of application is given by analysing the time series from three sea states concerning a swell, a wind sea and a mixed sea situation. It is shown how the power spectral density function changes with time and its nature when a wave group exists. The result suggests that the energy transfer from high to low frequencies does not occur continuously but in localized periods, exactly when the wave groups occur.
06/01887 Studies on simultaneous energy and water minimisation - Part I: systems with no water re-use Savulescu, L. et al. Chemical Engineering Science, 2005, 60, (12), 32793290. This paper addresses the simultaneous management of energy and water. A new systematic methodology has been developed for targeting and design that simultaneously minimizes the requirements of energy and water. Using this new approach, the design of a water system for maximum energy recovery can be achieved, taking into account the mixing opportunities offered by water networks, while maintaining the water quality to processes in terms of contamination. Direct and indirect energy recovery are analysed and a strategy developed to decrease the number of heat transfer units based on the generation of separate systems and non-isothermal stream mixing. Initially, the analysis is restricted to no water re-use.
06/01888 Studies on simultaneous energy and water minimisation - Part Ih systems with maximum re-use of water Savulescu, L. et al. Chemical Engineering Science, 2005, 60, (12), 3291 3308. A new systematic design methodology has been developed for the simultaneous management of energy and water systems that also feature maximum re-use of water. A two-dimensional grid diagram is proposed to exploit different options within water systems and also enable reduced complexity of the energy and water network. Isothermal and non-isothermal stream mixing between water streams are introduced to create separate systems between hot and cold water streams in the energy composite curves and provide a design basis for a better structure with fewer units for the heat exchanger network. In addition to allowing re-use of water, issues about heat losses inside unit operations have also been incorporated in the simultaneous management of water and energy.
06/01889 Surface configuration relevance in the overall thermal resistance of a wall Pires, L. et al. Energy and Buildings, 2005, 37, (10), 1068-1074. In the present work studies of experimental nature were made to evaluate the importance of the wall surface configuration related to its overall thermal resistance. A parameter with major importance in the value of such resistance is the convection heat transfer coefficient. In this way, several different surfaces were built and the correspondent convection coefficient was determined for natural convection conditions. As a reference for the comparative study a smooth surface has also been constructed. The value of the convection coefficient for each surface was obtained with the help of an infrared thermography system. The obtained results show a reasonable reduction in the smooth surface convection coefficient, which leads to an increase in overall thermal resistance. Therefore, if the objective is to increase the heat transfer rate between a surface and its neighbours there should be used roughness surfaces.
06/01890 Thermoacoustic instabilities: should the Rayleigh criterion be extended to include entropy changes? Nicoud, F. and Poinsot, T. Combustion and Flame, 2005, 142, (1-2), 153-159. The Rayleigh criterion (which measures the correlation between pressure and heat release) is the standard tool used to investigate and predict combustion instabilities in both experimental and numerical studies. However, the Rayleigh term is just one of the terms appearing in the acoustic energy equation. The recent development of large eddy simulations for combustion chambers allows complete closure of the budget and analysis of all terms in this equation. This task leads to unexpected difficulties and requires some basic work, as multiple definitions of the energy of fluctuations in a reacting compressible flow can be derived. The objective of this article is to revisit the theoretical derivations of the fluctuation energy equations. Two forms of energy are defined: The first is the classic acoustic energy (AE) introduced by various authors. The second is the fluctuation energy (FE) presented in an earlier study by B.T. Chu. Both equations are rederived in a compact manner starting from full nonlinear forms. It is shown that the classic Rayleigh criterion naturally appears as the source term of the AE equation, while the FE form leads to a different criterion stating that temperature and heat release must be in phase for the instability to be fed by the flame/acoustics coupling. The FE form also integrates the fluctuations of three variables (pressure, velocity, entropy), while the AE form uses only pressure and velocity perturbations. It is shown that only the FE form should be used in flames, in contradiction to many current studies performed for combustion instabilities.
06/01891
Transmissive diamond photocathodes
Foord, J. S. et al. Carbon, 2005, 43, (9), 2106 2111. The first studies are reported on the characteristics of ultra-violet transmissive mode, chemical vapour deposition (CVD) diamond photocathodes, in which photoelectrons are emitted from a diamond membrane via the opposite interface from that of the incident radiation. For membranes in the thickness range 5-40 ~tm, the transmissive photoyield at threshold wavelengths is shown to be less but comparable to that measured for reflective, thick film diamond photocathodes. The characteristics are found to be insensitive to the phase purity of differing diamond membranes used, but are very dependent on whether the growth or substrate interfaces of the diamond membrane face the incident UV radiation. The factors influencing the characteristics observed are discussed.
06/01892 Two-dimensional C5G7 MOX fuel assembly benchmark calculations using the FEM-PN code EVENT Keller, S. E. and De Oliveira, C. R. E. Progress in Nuclear Energy, 2004, 45, (2-4), 255-263.
Fuel and Energy Abstracts
July 2006
285