A new geometrical framework describes the phenomenon of scale-and time-dependent dimensions observed in a great variety of multiscale systems and particularly in the field of turbulence. Based on the notions of scale entropy and scale diffusivity, it leads to a diffusion equation quantifying scale entropy and thus fractal dimension in scale space and in time. For a stationary case and a uniform sink of scale entropy flux, the fractal dimension depends linearly on the scale logarithm. Here, this is experimentally verified in the case of turbulent-flames geometry. Consequences for temporal evolution of scalar passive-turbulent interfaces are investigated and compared with experimental data. Finally, some aspects of dynamics exchange between spatial scales in a turbulent jet are also studied.
In this paper, exergy analysis is used to evaluate the performance of a combined cycle: organic Rankine cycle (ORC) and absorption cooling system (ACS) using LiBr-H 2 O, powered by a solar field with linear concentrators. The goal of this work is to design the cogeneration system able to supply electricity and ambient cooling of an academic building and to find solutions to improve the performance of the global system. Solar ACS is combined with the ORC system-its coefficient of performance depends on the inlet temperature of the generator which is imposed by the outlet of the ORC. Exergetic efficiency and exergy destruction ratio are calculated for the whole system according to the second law of thermodynamics. Exergy analysis of each sub-system leads to the choice of the optimum physical parameters for minimum local exergy destruction ratios. In this way, a different connection of the heat exchangers is proposed in order to assure a maximum heat recovery.
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