Publications

This paper describes a new water-quality model that allows incomplete mixing at pipe junctions in water distribution networks. The bulk advective mixing (BAM) model honors momentum transfer and separation of impinging fluid streams within a cross junction. The solution is predicated on observed flow patterns in computational fluid dynamics simulations, which were confirmed by experiments, and a mass balance that ensures solute mass is conserved. This paper focuses on the implementation of this new model in EPANET, software that models hydraulics and water quality in water distribution networks. In the new version, EPANET-BAM, a mixing parameter, s, is implemented that allows the user to select the bulk advective mixing model (s = 0), the existing complete mixing model (s = 1), or a result that is linearly scaled between the results of the two models. Aside from the mixing parameter, which has been added to the junction property field within EPANET, all other functions of the BAM model are transparent to users of EPANET-BAM. This paper presents an example of the use of EPANET-BAM and the potential impact of the new model on water quality predictions and risk assessments. ©ASCE 2009.

Solid particle receivers have the potential to provide high-temperature heat for advanced power cycles, thermochemical processes, and thermal storage via direct particle absorption of concentrated solar energy. This paper presents two different models to evaluate the performance of these systems. One model is a detailed computational fluid dynamics model using FLUENT that includes irradiation from the concentrated solar flux, two-band re-radiation and emission within the cavity, discrete-phase particle transport and heat transfer, gas-phase convection, wall conduction, and radiative and convective heat losses. The second model is an easy-to-use and fast simulation code using Matlab that includes solar and thermal radiation exchange between the particle curtain, cavity walls, and aperture, but neglects convection. Both models were compared to unheated particle flow tests and to on-sun heating tests. Comparisons between measured and simulated particle velocities, opacity, particle volume fractions, particle temperatures, and thermal efficiencies were found to be in good agreement. Sensitivity studies were also performed with the models to identify parameters and modifications to improve the performance of the solid particle receiver.

A model has been developed to simulate the performance of a prototype solid particle receiver that was recently tested at Sandia National Laboratories. The model includes irradiation from the concentrated solar flux, two-band re-radiation and emission with the cavity, discrete-phase particle transport and heat transfer, gas-phase convection, wall conduction, and radiative and convective heat losses. Simulated temperatures of the particles and cavity walls were compared to measured values for nine on-sun tests. Results showed that the simulated temperature distributions and receiver efficiencies matched closely with trends in experimental data as a function of input power and particle mass flow rate. The average relative error between the simulated and measured efficiencies and increases in particle temperature was less than 10%. Simulations of particle velocities and concentrations as a function of position beneath the release point were also evaluated and compared to measured values collected during unheated tests with average relative errors of 6% and 8%, respectively. The calibrated model is being used in parametric analyses to better understand the impact and interactions of multiple parameters with a goal of optimizing the performance and efficiency of the solid particle receiver.

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