A Mathematical Model of a Solar Collector Augmented by a Flat Plate above Reflector: Optimum Inclination of Collector and Reflector

In this study a theoretical analysis of a collector augmented by a bottom booster reflector is presented. An analytical model has been developed and used to estimate the solar irradiation passing through the transparent cover of a flat collector, both with and without a bottom reflector. The analytical model is based on the anisotropic sky model and takes into account a finite length system with different angular configurations and reciprocal shading and reflections between reflector and collector. Computer simulations have been carried out in order to find the optimum angles of the reflector with respect to the plane of the collector. Optimal inclinations of the collector and reflector for each month at 39° N latitude have been identified

A novel model for uncertainty propagation analysis applied for human thermal comfort evaluation

The comfort sensation is mainly affected by six variables: air temperature, mean radiant temperature, air velocity, relative humidity, personal metabolism and clothing insulation. These are characterized by different mean values and distributions. To analyze the uncertainty propagation three numerical models are used: the Fully Monte Carlo Simulation MCSs, the Monte Carlo Simulation Trials MCSt, and a novel model named "Adaptive Derivative based High Dimensional Model Representation" (AD-HDMR). In the paper these three different methods are applied to the thermal comfort evaluation, through the PMV Index, they are analyzed and their efficiency was verified in terms of computational time. To allow a revision of this index, the effect of the different variables was then analyzed

Rheology of Conductive High Reactivity Carbonaceous Material (HRCM)-Based Ink Suspensions: Dependence on Concentration and Temperature

The present case study reports a shear rheological characterization in the temperature domain of inks and pastes loaded with conductive High Reactivity Carbonaceous Material (HRCM) consisting mainly of few-layers graphene sheets. The combined effect of filler concentration and applied shear rate is investigated in terms of the shear viscosity response as a function of testing temperature. The non-Newtonian features of shear flow ramps at constant temperature are reported to depend on both the HRCM load and the testing temperature. Moreover, temperature ramps at a constant shear rate reveal a different viscosity-temperature dependence from what is observed in shear flow ramps while maintaining the same filler concentration. An apparent departure from the well-known Vogel-Fulcher-Tamman relationship as a function of the applied shear rate is also reported

Computational Model For The Estimation Of Thermo-Energetic Properties In Dynamic Regime Of Existing Building Components

The guidelines of the European community towards a low-carbon economic society identify one of the most important scenarios in the energy efficiency of existing buildings. The discrepancy between the requirement and availability of free heat (endogenous heat, solar radiation) in certain hours of the day and operating conditions, makes the steady-state hypothesis generally inappropriate. In particular, the oscillating component of the transmitted flow, compared to the average temperature difference, is regressive in winter and dominant in summer. From this it follows the reliability of the stationary forecast models in winter and the need for dynamic forecast models in summer. The dominance of the continental climate in the EU, compared to the Mediterranean one, led to the actual delay in the development of dynamic models, especially at a regulatory level. In this paper, a methodology for assessing the dynamic properties of a building component is evaluated. The methodology, based on heat transmission equations implements a numerical model for existing building components whose input data can be obtained from experimental measurements. The developed model has been used to estimate the energetic and thermal behaviour of a building envelope subjected to energy efficiency measure

Uncertainty based optimal planning of residential building stocks retrofits

In this work the uncertainties related to the optimal planning/allocation of government subsidies for residential building stocks retrofits are considered and the uncertainty based planning problem is formulated and solved as a multi-objective, constrained problem. Different multi-objective algorithms are considered with the idea to determine the most effective and efficient approach that can be customized as planning tool to be used by the public administration personnel. The preliminary comparison between 2 multi-objective evolutionary algorithms and a deterministic one is presented and optimal/pareto results are analysed

Application of a Novel Method for a Simulation of Conductivity of a Building Material in a Climatic Chamber

This work proposes the application of a new simulation method based on fractal geometry for the calculation of the thermal conductivity for building materials. The results obtained are compared with the measurement, in a climatic chamber, of the heat flow through a material chosen as the sample. The test sample is made with “pietracantone”, a stone widely used as a building material and as an ornamental stone in the areas of Cagliari and Sassari in Sardinia. This material is characterized by a limestone matrix and a porosity which significantly influences the value of thermal conductivity. It is not known to the authors that this material had already been studied for its thermal propertie

Lezioni interattive nell’aula universitaria. Aumentare l’attenzione e la partecipazione usando i dispositivi degli studenti (BYOD)

Il contributo presenta una esperienza pilota svolta all’Università di Cagliari con gli studenti di “Fisica tecnica ambientale” del corso di laurea in Scienze dell’Architettura. Nel tentativo di rendere più produttiva e, allo stesso tempo, meno faticosa la frequenza delle lezioni teoriche durante l’anno accademico 2014/15 si è sperimentato l’uso di sequenze di domande e risposte gestite con e senza le tecnologie. Il lavoro, che proseguirà il prossimo anno, si è concentrato sull’accettabilità da parte degli studenti

Mechanization in harvesting saffron: an opportunity for economic development in Sardinia

In last decades it can be seen a strong growth of the biologic sector. In UE and USA in last years about 15-20 millions of Euro is the market value. The Sardinian Saffron spice DOP is certainty a biologic product. The saffron spice production is actually marginal because of high cost of the production phases, overall the harvesting phase of the flower on field, that is completely made by hand. The saffron harvesting mechanization is a winning chance also under a socio-economic point of view. A good answer to the too high harvesting and separating phases costs, is an integrated system to obtain the spice stigmas for successive drying and packaging phases of production. Main parts of the system are the harvesting device and the double cyclone separator plant. Two harvesting devices will be described, presenting the operating principle and describing the performances on field; in addition, the double flow cyclone separator will be described and the performances will be evaluated, presenting a statistical overview of the on field activity