Parametric study on the thermal gradient of a small stratified domestic oil storage tank
A simplified one dimensional model for a small stratified domestic oil storage tank is used for a parametric study on the thermal gradient in the storage tank. The model is validated with experimental results and reasonably good agreement between experiment and simulation is obtained. The effects of measurable and physically adjustable parameters of the average charging flow-rate, the inlet charging temperature and the heat loss factor on the thermal gradient are investigated with the model.
Simulation of thermocline storage for solar thermal power plants: From dimensionless results to prototypes and real-size tanks
Abstract A single-phase one-dimensional model called CIEMAT1D1SF has been developed for characterizing the behaviour of thermocline tanks with an effective storage medium formed by either a liquid or a liquid and a packed-bed. Despite its simplicity, this model has been validated with experimental data and the results of tank performance are similar to those obtained by other authors using more complex simulation models. In order to obtain general results the thermal equation has been nondimensionalized and the resulting expression only depends on the parameter called dimensionless velocity, v ∗ . It has been observed that thermocline thickness decreases as v ∗ increases attaining a minimum value when v ∗  ⩾ 2350 while tank efficiency increases with v ∗ up to a maximum of about 87% also for v ∗  ⩾ 2350. From these results the design equation for building thermocline storage tanks with maximum theoretical efficiency has been established. Since this design equation depends on tank dimensions and thermal power, small thermocline tanks and hence prototypes are not expected to behave in the same way as large or real-size tanks. Therefore maximum efficiency guideline plots for thermocline tanks with different storage media have been presented for various temperature intervals. In these plots thermal power has proven to be the critical design parameter because the larger the power the higher the degree of freedom for choosing tank dimensions and hence storage capacity and charging/discharging time. Therefore, we strongly recommend the use of these guideline plots in the design process of thermocline prototypes.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.