A. Vázquez-Rodríguez

Sensitivity analysis of a green roof

ABSTRACT The aim of this article is to perform a sensitivity analysis in a building with a green roof system (GRS). The Monte Carlo method was applied to construct a distribution of the temperature inside the building (TIB) as a variable predictor with random samples of solar radiation, ambient temperature, evapotranspiration rate, and wind speed, as input contributions. The numerical model used in this study considers a macroscopic dynamic description of the heat transfer process in the GRS. The sensitivity of the GRS reveals that the TIB is linear with respect to input contributions, and the major changes are: ambient temperature, followed by radiation, evapotranspiration, and wind speed.

Natural Circulation Cooling Scram Transient Analysis in Advanced BWRs: Buoyancy Effects

In this study, the transient characteristics of a two-phase natural circulation core cooling in advanced boiling water reactors is investigated during a scram scenario. The natural circulation is controlled by the mean density difference between the coolant inside and outside of the core. The Boussinesq approximation was applied in the momentum equations for two-phase flow analysis that considers the buoyancy force, which is related with thermal effects. The results obtained in transient with the buoyancy force in the core were compared with the standard approximation. The found results for scram transient indicate that, for time–scale, a small trend is practically the same between Boussinesq and standard approximation, where the difference between them is small. However, for higher simulation time (8 to 12 s) the consequences of the drive force effects are appreciable.

The Transient Heat Transfer of a Pebble Fuel Considering Anomalous Diffusion

In this article, the transient behavior of the heat transfer in the fuel element of a pebble bed modular reactor is presented. The pebble fuel is a heterogeneous system that is made up of microsphere constitutes by UO2, pyrolytic carbon, and silicon carbide mixed with graphite. To describe the anomalous thermal diffusion in this complex system, a fractional constitutive law of non-Fourier type is applied. The numerical results of the temperature distribution with fractional model were compared with the classical heat transfer model. The numerical simulations during transient behavior of the anomalous thermal diffusion process are presented in the heterogeneous pebble fuel for different anomalous diffusion exponents.