16 Fuel science and technology (fundamental science, analysis, instrumentation)

04103138 Residential end-use energy simulation at city scale Shimoda, Y. et al. Building and Environment, 2004, 39, (8), 959 967. This paper describes a simulation model for predicting end-use energy consumption in residential sectors of a city or region. In this model, the annual energy consumption of a dwelling is simulated from the occupants' schedule of living activities, weather data and energy efficiencies of appliances and dwellings. By summing up the simulation results for various household categories, total energy consumption for the residential sector in a region can be estimated. In this paper, energy consumption for Osaka City is simulated. The result is compared with statistical data. The effects of energy efficiency standards and urban heat island phenomena are examined.

04/03139 Second-law based thermodynamic analysis of Brayton/Rankiine combined power cycle with reheat Khaliq, A. and Kaushik, S. C. Applied Energy, 2004, 78, (2), 179 197. The aim of the present paper is to use the second-law approach for the thermodynamic analysis of the reheat combined Brayton/Rankine power cycle. Expressions involving the variables for specific power- output, thermal efficiency, exergy destruction in components of the combined cycle, second-law efficiency of each process of the gas- turbine cycle, and second-law efficiency of the steam power cycle have been derived. The standard approximation for air with constant properties is used for simplicity. The effects of pressure ratio, cycle temperature- rallio, number of reheats and cycle pressure-drop on the combined cycle performance parameters have been investigated. It is found that the exergy destruction in the combustion chamber represents over 50% of the total exergy destruction in the overall cycle. The combined cycle efficiency and it s power output were maximized at an intermediate pressure-ratio, and increased sharply up to two reheat-stages and more slowly thereafter.

04/03140 Sensitivity analysis for a 14 MeV neutron benchmark using Monte Carlo and deterministic computational methods Fischer, U. et al Fusion Engineering and Design, 2004, 70, (3), 221-232. A sensitivity analysis has been performed for a 14 MeV neutron benchmark on an iron assembly, typical for a fusion neutronic integral experiment. Probabilistic and deterministic computational methods have been used in the sensitivity calculations with the main objective to check and validate the novel Monte Carlo technique for calculating point detector sensitivities. Good agreement has been achieved between the Monte Carlo and the deterministic approaches for the individual calculated sensitivity profiles, the uncertainties and the neutron flux spectra. It is thus concluded that the Monte Carlo technique for calculating point detector sensitivities and related uncertainties as being implemented in MCSEN, a local version of the MCNP4A code: with the capability to calculate point detector sensitivities, is well qualified for sensitivity and uncertainty analyses of integral experiments.

04/03141 Simulation of hydrogen-based hybrid systems using Hybrid2 Mills, A. and A1-Hallaj, S. International Journal of Hydrogen Energy, 2004, 29, (10), 991-999. A hydrogen-based hybrid system was designed and simulated using the renewable resources available in Chicago, IL. The simulation was based on the probabilistic model developed for the Hybrid2 simulation software. The system integrates a 6.5 kWp solar array and a 12 kW wind turbine with a 2 kW fuel cell, 8 kW electrolyser, and 3 kW hydrogen gas compressor to meet a varying load with a mean of 1 kW. The hydrogen generated by the electrolyser is stored in a large, high-pressure tank

3 (22m volume). The stored hydrogen provides energy for the fuel cell to meet the load when the renewable energy is insufficient. The performance of the system is described in detail along with the probabilistic models needed to simulate the hydrogen-based com- ponents. Over a period of 1 year the energy produced by the renewable power generators exceeded the load by 160%, and the system did not require additional hydrogen or fossil fuel to consistently meet the load using a very small battery bank.

04•03142 Simulations of low energy cascades in fcc Pu metal at 300 K and constant volume Valone, S. M. et al. Journal of Nuclear Materials, 2004, 324, (1), 41-51. Recently progress has been achieved with a modified embedded atom method (MEAM) potential for pure Pu. The MEAM potential is able to capture the most salient features of atomic volume and enthalpy of solid and liquid Pu metal as a function of temperature at zero pressure. The atomic volume difference between monoclinic (c~-phase) and fcc (~-phase) was captured nearly quantitatively. From molecular dynamics (MD) simulations, it was found that Pu, under these conditions, has an approximately 10 eV minimum displacement threshold energy, very low compared to most other fcc metals, and shows less crystallographic anisotropy in this minimum. At 0 K, the constant volume cell relaxes to

a rhombohedrally distorted structure, which is connected to the tow minimum displacement threshold energy. Split interstitials orient themselves in a <1 0 0> direction and migrate over a 0.056 eV barrier. Mono-vacancies migrate over a 0.84-1.00 eV barrier.

04/03143 SP=-A= elementary solutions in general geometry Montagnini, B. and Ravetto, P. Annals of Nuclear Energy, 2004, 31, (6), 619 646. For a restricted, but not trivial, class of neutron diffusing systems, namely those in which the total cross-section is constant everywhere ('constant sigma', or Cc~ systems), the one-velocity, isotropic scattering transport equation in general 3D geometry can he transformed without any approximations into a second-order integrodifferential equation that is formally identical to an energy-dependent diffusion equation. The latter equation, which can also be considered as the limit of the SP2N-] (or AN) system of equations as N--*eo, allows for a further transformation into a boundary integral form. If the Ccr system is made of homogeneous regions (each one with its own value of the scattering cross section), the Green function, or fundamental solution, to be used in each region can be worked out explicitly and is shown to involve a bilinear expansion in terms of the Case eigenfunctions. Such a structure is mirrored by the structure of the solution of the transport problem, which can also be given the form of a (regionwise) superposition of these eigenfunctions.

04/03144 The function estimation in predicting heat flux of pin fins with variable heat transfer coefficients Lee, H.-L. et al. Energy Conversion and Management, 2004, 45, (11 12), 1749-1758. This article solves the two-dimensional inverse problem of estimating the unknown heat flux at a pin fin base by the conjugate gradient method. In the estimating processes, no prior information on the functional form of the unknown quantity is required. The accuracy of the inverse analysis is examined by simulated exact and inexact measurements of temperature at interior locations of the pin fin. The numerical results show that good estimations on the heat flux can be obtained for all the test cases considered in this study. Furthermore such a technique can be applied to determine the heat flux acting on an internal surface, where a direct measurement is not feasible.

04/03145 The NRTL equation as a predictive tool for vapor- liquid equilibria Vetere, A. Fluid Phase Equilibria, 2004, 218, (1), 33-39. A simple modification of the NRTL equation proposed in a previous work is the basis for a new predictive method to calculate vapour- liquid equilibria (VLE) of binary liquid systems. The only analytical modification of the NRTL consists in inserting the ratio of the molar volumes of the pure compounds as a multiplying factor of the binary parameters G U and Gji. Further, the modified NRTL equation is applied in the one parameter form according to the method proposed by Tassios. The proposed procedure entails in some cases the following steps: (i) Energy parameters Gii and @j for the ~ I and j - j interaction are calculated from the enthalpy of vaporization of pure compounds. (ii) A modified form of the geometric mean is assumed for the cross- interaction parameters G U and Gil, namely G~i = G/~=Kij(GiiGi/) °5. (iii)/(,.-i is calculated for each class of compounds by simple rules related to well-known properties of pure compounds. (iv) Systems are grouped in the following classes according their non-ideality: nearly ideal systems, alcohols/polar compounds, polar/polar compounds, alcohols/ non-polar compounds, polar/non-polar compounds, miscible aqueous systems and alcohols/non-polar systems with a miscibility gap. The results show that the simple and general proposed method can be used as a rule of the thumb for a large number of binary systems.

04/03146 The optimum interior area thermal resistance model to analyze the heat transfer characteristics of an insulated container with arbitrary shape Wong, K.-L. et al. Energy Conversion and Management, 2004, 45, (7-8), 963-982. The heat transfer characteristics for an insulated regular polyhedron (or sphere) are investigated by using a regular polygon top solid wedge thermal resistance (RPSWT) model as well as the interior area thermal resistance model Rth = t/Ks/l(1 o~)A2 + c~A3] with a surface area weighting factor c~. The errors of the results generated by an interior area thermal resistance model can be obtained by comparing the exact results generated by an RPSWT model. The accurate solution can be obtained without error at the optimum O~op t with their relative t/R2. The relation between ~opt and t/R2 is C~op t = 1/(2 + t/R2). The value of O~op t is between 0-0.5 and is independent of container size Rz/Rcr but strongly dependent on the insulated thickness t/R2 (for example, t/R2 = 0.5, C~op~ = 0.4). The interior area thermal resistance model with the optimum value opt should also be applied to an insulated container with arbitrary shape within a small amount of error. The parameter R2 can be evaluated by measuring the container surface area A2 and letting A2 = 4~R22. It is also found that the conventional constant surface

Fuel and Energy Abstracts November 2004 441