Fabio Fantozzi

On the optimization of building envelope thermal performance

The optimal sequence of resistive and capacitive layers within building envelope is determined, in order to minimize the air-conditioning plant intervention to keep the indoor air temperature constant against sinusoidal and impulsive external temperature variations. In the case of sinusoidal variations with angular frequency ω, the optimal structure of the building envelope is determined by the value of the dimensionless parameter σ = ωrc only, where rc is the wall thermal time constant. For σ < 18 the interventions of the air-conditioning plant are minimized if the whole heat capacity is lumped between two plane slabs with the same value of the thermal resistance (symmetrical three-layered wall); for σ > 18 symmetrical walls are still preferable, but with a number of layers increasing with σ (walls with more than three layers); for σ → ∞ the optimal structure is the one of a homogeneous wall. In the case of impulsive stresses, the wall which facilitates the plant intervention, is a symmetrical three-layered one, as the previous case for low values of σ.

Thermal analysis of the building envelope of lightweight temporary housing

In the last few years, to meet the need of build efficient homes in a short time and with maximum constructive simplification, lightweight prefabricated building systems have proved to be particularly suitable, especially in geographical areas which must deal with emergency situations (i.e., temporary housing). In this paper the winter and summer thermal performance of a building prototype, realised with modular steel framed elements, have been studied, in both winter and summer conditions. Special attention has been paid to the optimisation of the dynamic thermal performance of the multi-layered envelope structures. The dynamic thermal behaviour of the outer wall, analysed and discussed in details in the paper, shows that it is possible to improve the performance of lightweight walls by using an optimised stratigraphy characterised by an opportune sequence of resistive and capacitive layers. The influence of inner structures (partitions, floor and roof) on the building thermal behaviour has also analyzed trough the introduction of room performance indices appropriately defined. The results of the study have been discussed with special reference to the requirements fixed by the Energy Performance Buildings European Directive (EPBDs) and the resulting implementation in Italian Legislation.

Pulsated two-phase thermosyphons for electronic equipment thermal control

This work proposes some heat transfer pulsating devices as interesting alternative solution to the LHP (Loop Heat Pipe) and CPL (Capillary Pumped Loop). These devices, named pulsated two-phase thermosyphon (PTPT) by the authors, have been studied, classified and experimentally observed in previous works. In this paper the operating principles of the PTPT devices in comparison with LHPs or CPLs for thermal control applications are illustrated. Although the LHP and CPL operate in a steady state regime of heat transfer and PTPT operates in a stabilized periodic regime, some important comparisons are presented. In conclusion the application of a PTPT could become a possible cheap choice in future in case of the thermal management of electronic devices.

Recognition of wall materials through active thermography coupled with numerical simulations

In the framework of historical buildings, wall thickness as well as wall constituents are not often known a priori, and active IR thermography can be exploited as a nonintrusive method for detecting what kind of material lies beneath the external plaster layer. In the present work, the wall of a historical building is subjected to a heating stimulus, and the surface temperature temporal trend is recorded by an IR camera. A hybrid numerical model is developed in order to simulate the transient thermal response of a wall made of different known materials underneath the plaster layer. When the numerical thermal contrast and the appearance time match with the experimental thermal images, the material underneath the plaster can be qualitatively identified.

Analysis and clustering of natural gas consumption data for thermal energy use forecasting

In this paper, after a brief analysis of the connections between the uses of natural gas and thermal energy use, the natural gas consumption data related to Italian market are analyzed and opportunely clustered in order to compute the typical consumption profile in different days of the week in different seasons and for the different class of users: residential, tertiary and industrial. The analysis of the data shows that natural gas consumption profile is mainly related to seasonality pattern and to the weather conditions (outside temperature, humidity and wind chiller). There is also an important daily pattern related to industrial and civil sector that, at a lower degree than the previous one, does affect the consumption profile and have to be taken into account for defining an effective short and mid term thermal energy forecasting method. A possible mathematical structure of the natural gas consumption profile is provided. Due to the strong link between thermal energy use and natural gas consumption, this analysis could be considered the first step for the development of a model for thermal energy forecasting.

Opportunities for energy savings with interventions on the lighting systems of historical buildings: The case of “Palazzo Medici” in Pisa, Italy

The energy audit for a building is a procedure designed mainly to obtain adequate knowledge of the energy consumption profile, identify and quantify opportunities for energy savings by a cost-benefit analysis and report, clearly and comprehensively, about the obtained results. If the audit is referred to a building with a significant historical and artistic value should be also developed a compatibility evaluation of the energy saving interventions with the architectural features. In this paper, discussing the energy audit carried out for the historical building named “Palazzo Medici” in Pisa (Italy), the Authors analyses, from a techno-economic standpoint, different possible interventions on the lighting systems aimed to obtain significant energy saving. The total of six interventions on indoor and outdoor lighting systems, analyzed in the paper, allow a reduction of about 35% of the electrical energy demands for the artificial lighting of indoor and outdoor spaces, with a very short payback times. From the results obtained by the Authors, it is possible to show that, for historical buildings used for public functions, interventions to improve energy efficiency of lighting systems may allow significant reductions in the electrical energy consumption, which, in some cases, may reach or exceed the 20% of the overall electrical energy consumption.

Risk assessment arising from exposure to artificial optical radiation: Results of an extensive evaluation campaign in the hospitals of Tuscany (Italy)

In this paper the Authors describe and discuss the results of an extensive evaluation campaign of optical radiation emitted by equipment provided with incoherent sources, commonly used in the hospitals of the Tuscany Region (Italy). The results of the evaluation campaign can be a useful database of technical information for the personnel involved in the risk assessment.