Despite their limitations, the cross flow compact heat exchangers are generally modeled by the ε-NTU and LMTD methods and this mainly leads to the absence of effective consideration on the heat transfer geometry at the micro scale. At the same time, numerical analysis applied to compact cross flow heat exchangers, having different and complex finned surfaces respectively at the hot and cold sides, involves high computational costs. A powerful alternative design procedure is here proposed that takes advantage of both numerical and analytical approaches. Hot and cold sides are numerically modeled and predictor functions for heat transfer and fluid dynamic performance are obtained with regression technique, for both sides. The whole cross flow heat exchanger is divided into a set of control volumes, including the fins geometry 3D accurate description of both sides and their separation wall. An analytic iterative method is then used to find a wall temperature distribution throughout and to determine the mass flow rate distributions on both sides starting from the results of the numerical analysis at the micro scale. The multi-scale approach leads to a better accuracy level with respect to the full-scale one and allows to profitably investigate different fins influence on flow distributions, local heat transfer and pressure losses through both sides of the heat exchanger.

The thermal-hydraulic phenomena in a pebble bed modular reactor (PBMR) core have been simulated under steady-state and transient conditions. The PBMR core is basically a long right circular cylinder with a fuel effective height of 11 m and a diameter of 3.7 m. It contains approximately 452,000 fuel pebbles. A three-dimensional computational fluid dynamic (CFD) model of the PBMR core has been developed to study the influence of porosity on the core performance after reactor shutdown. The developed model was carried out on a personal computer using ANSYS fluent 14.5. Several important heat transfer and fluid flow parameters have been examined under steady-state and transient conditions, including the coolant temperature, effective thermal conductivity of the pebble bed, and the decay heat. Porosity was found to have a significant influence on the coolant temperature, on the effective thermal conductivity of the pebble bed, on the decay heat, and on the required time for heat removal.

Evaporative condensers operate at lower temperatures and with a higher efficiency compared to air condensers, as heat rejection is limited by air wet bulb temperature and mainly caused by water vaporization. This reduces the compressor pressure-lift and improves refrigeration cycle performance. Due to complex phenomena of heat and mass transfer on the tube bundles, modeling the evaporative condensers is a hard task and fine grids in numerical simulations are requested to reach acceptable results. A two-dimensional steady state numerical model at the single tube scale has been developed in Ansys-Fluent (release- 14.5), adopting the VOF multiphase model. Moist air has been treated as a mixture of air and water vapor species, while water vaporization and latent heat have been modeled with a C++ User Defined Function. The tube wall temperature has been assumed constant. The aim of this work is to describe the developed numerical model and to validate it by comparing results obtained at different operating conditions with empirical relationships found in the literature in terms of combined and overall heat transfer coefficients. Combined heat transfer coefficient variation along the tube surface has been analyzed, observing that the heat transfer coefficient is higher in the impingement zone, becomes approximately uniform and rises approaching the trailing edge. Moisture content distributions at different sections through the heat exchanger have been examined in detail as well. This study will be the basis to investigate the performance of the whole condenser taking into account the real evolution of the operating conditions of each single tube in the bundle, whatever its arrangement.

The results about the performance of a new DAR's thermodynamic model are compared with the predictions of Zohar et al. (2009). The main difference is due to an accurate modeling of the refrigerant composition, assumed there as pure ammonia. A sensitivity analysis shows that, as the generator temperature increases, the rich solution mass flowrate reduces more than that of the refrigerant one, and COP decreases. This happens as the absorption temperature increases as well, due to the lower absorption of ammonia in the weak solution. COP was found to increase when the ammonia concentration decreases. In addition, for lower heat fluxes supplied to the generator, the heat dissipation toward ambient dominates and COP becomes small; when the heat flux overtakes a threshold, the evaporator reaches its maximum heat transfer, that remains constant for any further increase of heat supplied. COP presents its highest values over a limited range of the generator's operating conditions.

A steady state description of the thermal pump driving the Diffusion Absorption Refrigerator was integrated in the model previously proposed by the same authors. The thermal pump allows the DAR cycle to be activated, moving the strong mixture and separating the refrigerant from the weak one. So, the design parameters play a primary role in the DAR cycle performance in terms of COP. The enhanced model results were validated on a prototype built coupling a domestic 750 W-magnetron on a small purposely modified commercial DAR to activate the thermal pump. A maximum mismatch of 2.32% in the weak mixture mass flow rate and lower than 5% in COP between the predicted and measured data were found. The microwaves activated thermal pump produced a distinct reduction in the starting transient time of the refrigerator and for this reason it can be proposed as a valid candidate to be used as a rapid cooler in small refrigeration applications.

Descrive i risultati di una campagna sperimentale di caratterizzazione di telai piani di produzione svolta a fini di bonifica di un capannone industriale e con tecnica intensimetrica.

Descrive la metodologia e i risultati della progettazione avanzata di una bonifica acustica di un capannone adibito ad uso tessile. Sfrutta ed elabora i risultati sperimentali raccolti sui telai di produzione con tecnica intensimetrica.

This work deals with the efficiency and the energy behavior of Ground Source Heat Pumps (GSHPs) used for heating and cooling of buildings. In particular horizontal type heat exchangers have been investigated for different configurations, in order to evaluate the characteristics of these systems in the most common layouts and in different working conditions. The main results pointed out the heat fluxes transferred to and from the ground and the efficiency of the system. The calculations were made with the CFD code Fluent and the simulations covered one year of system operation, both in summer and winter for typical climate conditions of the South of Italy. The most important parameter for the heat transfer performance of the system resulted the thermal conductivity of the ground around the heat exchanger and the optimal ground type was that with the highest thermal conductivity (3 W/m K in the cases analyzed in this work). The choice of the velocity of the heat transfer fluid inside the tubes was another key factor. The depth of installation of the horizontal ground heat exchangers did not play an important role on the system performance. The helical heat exchanger arrangement resulted as the best performing one.

Il processo di produzione di syngas (gas di sintesi) per pirolisi e gassificazione di cippato di legno presenta una complessità rilevante dal punto di vista impiantistico, in particolare per la sua gestione automatica. Questa, in tutte le sue fasi è influenzata da un elevato numero di fattori. Questo lavoro descrive le modalità e i risultati di quanto sviluppato in ambiente Labview 8.5 - National Instruments nell’applicazione di logiche e strumentazioni a un sistema di produzione di energia elettrica da biomassa (cippato di abete), basato su di un gassificatore a letto fisso (in configurazione downdraft) e su di un motore alternativo a combustione interna di 150kWel, realizzato presso la SOCOGES Srl di Monopoli (BA).

The defense mechanism of crops associated with the use of polymeric nets and fabrics is only physical and, hence, ineffective against the bacterial contaminations. The presence of an antibacterial agent associated with the use of conventional agro-textiles can represent a great advantage in the prevention of plant diseases and for food safety. The aim of this work was the development of antibacterial silver-coated HDPE nets for an innovative application such as agriculture. Antibacterial coatings on high-density polyethylene nets were obtained by a patented nanosilver deposition technique based on the in situ photo-reduction of a silver solution. The concentration of silver deposited was defined by testing different silver solutions from a biological point of view. Moreover, in order to improve the adhesion of the silver coating to the substrate, the nets underwent low-pressure plasma treatment before the silver deposition. The materials were characterized in terms of quality of the coating through scanning electron microscopy, and in terms of antibacterial capability on Gram positive and Gram negative bacteria through qualitative and quantitative microbiological tests. The most effective process parameters were defined and the importance of performing plasma pretreatment on this specific substrate was assessed.

In this work, the thermal behavior of a new Exhaust Gas Recirculation (EGR) valve, installed on a series Diesel engine, was examined to identify effective thermal loads on it, during its real operation. Both theoretical tools and experimental set-up were used to achieve feasible results. The two different theoretical approaches used were respectively at steady and unsteady operation. They were set-up to account for the complex thermal resistances network, due to different materials used and for the interaction of heat loads on components, due to their different thermal inertia and the characteristic operation of the valve, modelling both conduction and convection phenomena. Some tests on a engine bench have been carried out to validate theoretical models. An instrumented EGR valve was used, provided with thermocouples mounted on particular locations, inside and outside the valve. A good matching between theoretical and experimental results was found. Critical components were located in terms of reached thermal limits and a basis for improvement proposals was defined to reduce valve failure, due to thermal loads.

In order to evaluate the influence of the texture characteristics of agricultural nets on the air flow passing through, a micro wind tunnel was built in the “Testing and Engineering Laboratory” at the Sachim SRL, an Italian HDPE technical textiles manufacturer. The wind tunnel allowed setting up the inclination of the net samples inside with respect to the air flow (90° perpendicular, 60°, 45°, 30°). First results in terms of coefficient of discharge of 4 flat woven round monofilament HDPE nets are reported in this paper. The net response to the air flow was based on the discharge coefficient approach based on BernoulliRSQUOs theory. Results confirmed the parabolic dependence of the pressure drop on the square of the velocity and on the porosity by means of the parameter (1-ε2)/ε2. Concerning the influence of inclination of the net on loss coefficient, a correlation with sen2θ was found, described by an exponential regression curve depending on the porosity of the net.

The evaporative condensers operate at lower condensing temperatures compared with dry heat transfer units when connected to the same refrigeration system, as well as involve less water and reduce the pumping power associated to cooling towers. These characteristics are strictly correlated with the evaporation process. For these reasons they are conveniently used for heat rejection in big industrial plants and recent technological developments have made it possible to exploit their higher efficiency even in smaller air conditioning systems. In this work a test rig for the evaporative condensers performance analysis and the relevant experimental activities are presented. The combined effect of the dry bulb temperature and relative humidity on the system performance has been investigated. The maximum reduction of the heat transfer rate, due to an increase of 6 % of the initial value of relative humidity, results of 30 % for the highest dry bulb temperature. The air processes plot in a psychrometric chart show that the latent to sensible heat transfer ratio decreases with relative humidity.

The evaporative cooling is an energy saving technology and for this reason is widely used both in industrial and civil fields. The heat and mass transfer phenomena occurring inside their tube banks are hard to study and even if many researchers have faced them, further activities need to be carried out. For this reason, this work aims at investigating with an experimental approach the evaporative condensers performance at the tube scale, focusing on the air side where more complex physical interactions occur. A test rig has been set up made of a rectangular transparent channel where electrical heaters simulate the refrigerant side and embedded Pt100 Resistance Temperature Detectors controlled by a PID set and keep constant a given outer surface temperature. Water and air operating conditions are controlled as well, and this allows to carry out a sensitivity analysis depending on all the parameters influencing those thermo-fluid dynamic phenomena. The results show that the cooling rate decreases with the air relative humidity and dry bulb temperature, while increases with water flow rate and temperature. For the testing cases the maximum improvements deriving from increasing water flow rate and temperature are of 37 % and 14 % respectively.

Nanofluids belong to a new generation of heat transfer fluids. Their thermal properties make them suitable to be employed in high-performance energy systems. In this paper a new setup for investigating the interactions between microwaves and nanofluids is presented. This is a new issue in this field and only one other experimental campaign has been carried out in the scientific world so far. The design of this experimental setup together with the preliminary results on two different water-based nanofluids (Al2O3 and CuO nanofluids) opens a new frontier in the field of heat transfer in nanofluids.

Basi della termodinamica - Cicli termodinamici - Aria umida - Trasmissione del calore

Greenhouse farming, where energy con- sumptions are mainly related to the greenhouses heating, is one of the sectors consuming the most energy in the agricultural industry. High costs and the uncertain availability of fossil fuels constrain the use of heating applications. Among possible solutions, the utilization of renewable heating systems such as geothermal energy through ground-source heat pump systems (GSHPs) at competitive prices has to be taken in consideration. The competitiveness of these systems depends mainly on the characteristics of the end-users, i.e., the annual heating loads. Few studies focusing on the potential of using these systems start with an analysis of the thermal re- quirements and end with a cost evaluation in tune with local assets, geo-climatic conditions, and landscape pro- tection. This paper analyzes the greenhouse crop indus- try in the Apulia region in southern Italy, as a potential end-user of GSHP systems. Data collected from an area mainly devoted to greenhouse crop production have been used to (a) describe greenhouse farms, (b) define the heating requirements of a greenhouse model repre- sentative of the most used typology in the investigated area, and (c) examine the economic viability of green- house heating with GSHP systems. Both vertical and horizontal ground heat exchanger (GHE) configurations are compared with conventional fossil-fuel heating sys- tems. In all scenarios considered, the observed payback periods appear reasonable and worthy of consideration. The results suggest that these technologies can fully satisfy the winter heating requirements in a cost- effective way and they can support the planning of measures aimed to improve the sector competitiveness.

Facendo uso dell’ambiente di programmazione TRNSYS, si è condotta un’analisi sulle prestazioni di impianti integrati solare-geotermico utilizzati per la produzione di acqua sanitaria e per la climatizzazione invernale. Il caso di studio di partenza è quello di un’abitazione mono-familiare sita a Brindisi. Creati e testati, dapprima in maniera separata, i modelli di impianti solare e geotermico sono, poi, stati integrati nell’ottica di utilizzare l’acqua calda proveniente dal collettore solare termico nel circuito idronico di scambio a terreno della pompa di calore per mantenerne alta la temperatura di evaporazione. Per questa applicazione, i miglioramenti in termini di consumi e di efficienza dell’impianto prodotti con l’approccio integrato si sono rivelati più ridotti delle attese. Gli studi hanno, in seguito, riguardato le prestazioni dell’impianto integrato in diverse configurazioni caratterizzate da differenti proporzioni tra la superficie dei collettori solari e l’accumulo termico. Lo stesso modello è stato poi applicato a utenze del tipo ufficio con risultati più incoraggianti.

Rising energy costs, increasing requirements in terms of home energy efficiency and greater environmental awareness have brought about great interest in gas absorption heat pumps (GAHP). These systems provide high thermal comfort combined with high energy efficiency and CO2 reductions when compared to state of the art condensing boilers. The gas absorption heat pump uses primary energy (natural gas) directly, which means that it does not require highly exergetic electricity as driving energy for the heat pump process. The gas absorption heat pump subject of this paper uses outside air as renewable heat source. Modeling and simulation is applied in order to gain insight into the main characteristics of the GAHP thermodynamic cycle. The paper presents a modular, steady-state model for the simulation of an air sourced gas absorption heat pump operating with an ammonia-water mixture. The GAHP refrigerant circuit is designed as a GAX cycle (Generator Absorber heat eXchanger) which boosts the efficiency of the unit by recovering the heat that is released from the absorption process. Modeling is based on heat and mass balances for each component. Investigation the cycle performance requires calculation of the thermodynamic properties of the ammonia-water solution. The model uses the equations presented by Ziegler and Trepp (1984), based on the equations of state provided by Schultz (1971). The bubble point temperature and the dew point temperature are computed from the explicit relationship developed by El-Sayed and Tribus (1985). The model was implemented in MODELICA/DYMOLA. It calculates the heat pump heating power as a function of the water temperature at the inlet and outlet at different outdoor air temperatures. The results are compared with some manufacturer data reported in the open literature. In general a very good agreement between the simulation results and the experimental data is found. The model is then used to investigate the influence of important design and operating parameters on the performance of the gas absorption heat pump.

È oggetto di questo studio l’elaborazione di un modello matematico sviluppato in ambiente Mathcad in grado di simulare il funzionamento di scrubber verticali ad acqua in controcorrente (torri di lavaggio) per la pulizia di syngas da gassificazione di biomasse lignocellulosiche, ai fini del suo utilizzo in un motore a combustione interna. Il modello calcola il numero di stadi necessario a soddisfare le specifiche prestazionali dello scrubber in termini di efficienza di abbattimento del particolato e di raffreddamento della corrente gassosa e fornisce indicazioni progettuali sulla scelta dei parametri geometrici e funzionali. La variazione imposta dei parametri funzionali consente, poi, di condurre un’analisi dell’output progettuale, in particolare al variare del rapporto tra portata d’acqua immessa e polverizzata e portata di syngas, della dimensione media dei contaminanti da rimuovere e della temperatura di ingresso nello scrubber.

The heat rejection of industrial plants is often made with evaporative condensers as their choice meets energy efficiency requirements. In this work some numerical simulations of the evaporative condenser heat and mass transfer processes were carried out at the tube scale: 2D and 3D approaches were performed using the Ansys Fluent R.16.2 (VOF model). The time resolved characteristics of the film flow process were studied and two different types of flow (stable film and drops mode) were investigated, by varying the water-to-air mass flow ratio. The decrease of the water-to-air mass flow ratio was found that led to the film break-up into droplets. An experimental test rig was designed and built up for future validation works and to give designers new relations to quantify heat transfer performance depending on real working conditions.

Falling film evaporation over horizontal tubes consists of simultaneous heat and mass transfer processes: in an evaporative condenser it improves the heat rejection from the condensing refrigerant to the air. The liquid flow is generally influenced by viscous, gravity, tension effects, liquid mass flow rate, tube diameter and spacing and distance from the feeding system. In this work, a two-dimensional numerical model of the falling film evaporation on horizontal tubes is presented. The temporal change characteristics of the film flow process were studied and different types of flow (stable film and drops mode) were investigated, by varying the ratio between the water-to-air mass flow ratio. The effect of the tubes arrangement on the flow mode was analyzed too: an increase of 73% of the longitudinal pitch corresponds to an increase of 66.7% of the minimum water mass flow rate that prevents the film break-up. The trade-off curve for a given geometry was obtained: at a specific air mass flow rate, a transition zone between the stable film to the drops mode conditions was individuated, with an uncertainty of 10% referring to a water mass flow rate variation of 10%.

Artificial drying, using industrial devices (dryers), helps to reduce the residual humidity content in biomass in a relatively short time. Convection is one of the most common mode of drying (referred to as direct drying). Heat is supplied by hot air/gas flowing over the surface of the solid. The heat for evaporation is supplied by convection to the exposed surface of the material; the evaporated humidity is carried away by the drying fluid. Indirect dryers (working by conduction) are more appropriate for particulate and granular materials or for very wet solids; while radiative dryers use various sources of electromagnetic radiation with wavelengths ranging from the infrared to microwaves. In this work, two mathematical models of cross flow and rotary dryers (both convective dryers) have been proposed. Both dryers treat wood chips. The two models allow to calculate the thermal efficiency and residence time of wet solid wood chips, as a function of the residual moisture content, as well as the analysis of the behaviour of the outlet wet solid and drying gas, in consideration of the dryer length and of the feeding material conditions in the dryer. The models have been developed in the Mathcad software environment.

Nel caso di impianti in cui si disponga di cascami termici o di energia termica a basso costo, in alcune situazioni, per esempio quando per i motivi più diversi non siano utilizzabili le macchine frigorifere tradizionali, la tecnologia ad assorbimento può giocare un ruolo decisivo nel soddisfare la richiesta di potenza frigorifera. La possibilità che le macchine ad assorbimento possano essere alimentate ad energia da fonte solare o con il calore di combustione della biomassa lascia intravedere anche la possibilità di applicazioni di grande interesse in termini di risparmio di combustibile fossile e quindi di riduzione delle emissioni inquinanti in atmosfera. Il testo, partendo da una descrizione dettagliata dei fondamenti teorici e dei modelli di calcolo analitico delle prestazioni dei componenti delle macchine e dei sistemi esistenti, si pone l'obiettivo di riassumere lo stato dell'arte del settore, passando dalle soluzioni più semplici e comuni a quelle con ancora sperimentate nella pratica impiantistica. Brevetti, schemi funzionali delle macchine prodotte dai vari costruttori mondiali, accorgimenti tecnici adottati, controlli del ciclo termodinamico, operazioni di gestione e manutenzione, approfondimenti sulle numerose applicazioni dei refrigeratori e così via vengono trattati in maniera sistematica. L'ultimo capitolo è dedicato alla refrigerazione per adsorbimento che, pur essendo dal punto di vista teorico simile a quella ad assorbimento, se ne differenzia per l'applicazione a livello impiantistico e realizzativo.

The evaporative condensers operate at lower condensing temperatures with respect to dry condensing units and involve reduced water consumption if compared with water cooled condensers. A test rig to investigate the evaporative condenser at small scale has been designed and built up. The condensing refrigerant has been simulated by electrical heaters and an air handling unit provides air with dry bulb temperature and relative humidity set by the user. All the c affecting the evaporative condenser performance can be monitored and adjusted, in order to carry out either an extensive experimental campaign or a sensitivity analysis. The results, as expected, clearly show that the heat released to air increases with the outer surface temperature of electrical heaters and decreases with relative humidity. An increase of 37.5% of the air flow rate (at constant sprayed water) leads to a maximum reduction of the heat transfer rate of 50%. Different tubes arrangements have been compared, showing as a decrease of the transversal pitch involves worse performance.

The interest in the absorption refrigeration systems continuously grows in many applications as they can exploit either waste heat or both traditional fuels and renewables (natural gas, sun, geothermal, biomass) as primary energy. Among several configurations of absorption cycles the GAX (Generator/Absorber/heat eXchanger) one plays an important role and allows to achieve good energy efficiencies of energy utilization with no relevant increase in system complexity. Here the analytical models of both GAX and GAX Hybrid (GAX-H) absorption cycles using ammonia–water mixture as working fluid are presented. Developed in Matlab R2010a, they simulate mass and energy conservation laws in each system component. The thermodynamic properties of ammonia-water solution are calculated based on the equations by Ziegler and Trepp, on the equations of state by Schultz and on the explicit relations for the bubble point and the dew point temperatures by El-Sayed and Tribus. The developed models were run to investigate the influence on the overall cycles’ performance of the generator, the condenser and the evaporator temperatures, of the absorber pressure and of the heat exchanger effectiveness. Results show the general trends of the efficiency of the cycles and allow the comparison between GAX-H and GAX cycles. When a pressure ratio of 1.5 between the absorber and evaporator pressure is maintained, the GAX-H COP (Coefficient Of Performance) is 50% and 32% higher than the conventional GAX cycle one operating with a degassing range of 0.2, 0.3 respectively.

The heat and mass transfer in evaporative condensers are complex to model analytically and numerical simulations, when applied to multi-phase fluid dynamics in complex paths, often involve too high computational costs. Experimental campaigns at full scale of different heat transfer geometries and tube arrangements involve long lead times and high costs as well. The aim of the present work is to overcome the present limitations and to apply a new method to evaluate the overall performance of the countercurrent evaporative condensers, starting from the experimental, numerical or analytical data with a small scale approach. A test bench has been purposely designed and built up in order to reach and keep constant all the parameters determining the evaporative condenser heat transfer performance. In previous experimental contributions available in the literature, the air conditions were not controlled: here, an air handling unit placed before the evaporative condenser inlet allows to set up temperature and relative humidity of air in large ranges. An extended experimental campaign has been carried out to get affordable data to be used to find a relationship correlating the dry bulb temperature and relative humidity of air after its interaction with water and the condenser tubes surfaces, while all the parameters were set up and controlled. The regression function fits well the experimental data as the predicted values of temperature and relative humidity are characterized by a maximum percent deviation lower than 2.5% and 4% respectively. An iterative procedure was then implemented to determine the conditions of air going through the evaporative condenser in order to extend small scale results to full scale performance according to real geometries. The effect of the water flow rate on the cooling capacity was investigated and the results show that an increase of 50% of the sprayed water leads to an increase of 14% of the performance.

This chapter focuses on the Diffusion Absorption Refrigerator (DAR) cycle and describes a new advanced thermodynamic model which allows good predictions of the chiller performance in terms of efficiency and cooling capacity, starting from a precise evaluation of the thermo-physical properties of the working mixture at each point of the circuit. A steady state thermodynamic analytical model of the thermal pump driving the DAR is also included. In addition, the experimental validation of the model, performed on a prototype built coupling a domestic 750 W-magnetron with a small purposely modified commercial DAR to activate the thermal pump, is here included: a maximum mismatch of 2.32% in the weak mixture mass flow rate and lower than 5% in COP between the predicted and measured data were found.

A procedure for the design and rating of plate-finned tube evaporator is proposed, to overcome limitations of both numerical and experiment based available present methods. The hybrid method allows to achieve high accuracy without incurring excessive computational cost and provides overall performance predictions starting from local analyses. The domain is divided into control volumes, where heat transfer is modeled by means of predictor equations obtained by known data. An iterative analytical method is used to find at each control volume the convergence between the heat transfer rates on both sides, and to obtain the distribution of wall temperature in the heat exchanger and the spatial distribution of the air mass flow rate. A case study is shown where in the first row the refrigerant completely evaporates, while this doesn't happen for the last one where the vapor quality at the outlet is 28% lower.

Assessing sustainability of manufacturing processes through LCA tools is a common approach today, but it suffers some limitations, mainly due to the use of standard databases. Deepening the assessment of sustainability is, instead, a new field of interest. This paper shows how LCA can be optimized, based on the results of a thermographic analysis supplying detailed information to a traditional LCA tool. The aim is to test this this approach observing a real industrial case of an Italian company producing High Density PolyEthylene (HDPE) nets for agriculture. A thermographic analysis of the critical processes helps in assessing the in-progress eco-profile of the process under investigation. The approach is intended as an iterative procedure to make both LCA analysis much more pertinent to the specific application and decisions on process sustainability more adherent to real practice. The improved LCA allowed to balance the specific energy savings intervention (recognized by the grace of thermographic analysis) by benchmarking the potential process quality improvements with standard reference processes. These balanced design choices and improvements can avoid useless over-dimensioning of the devices. In turn this can help to reach sustainable quality of both products and processes

LCA (Life Cycle Assessment) is nowadays a commonly implemented approach for evaluating resource consumptions and for benchmarking purposes. It suffers some limitations, mainly related to its assumptions on linear resource -consumption behaviour as well as on the non-context specific data. On the other hand, it is an extremely powerful tool for decision-making support in the sustainability assessment of manufacturing processes, providing its well-structured approach and widely accepted procedure. Deepening the assessment capabilities of such a tool is thus an important opportunity

Obiettivo del lavoro è l’analisi del fenomeno della sedimentazione dei nanofluidi all’interno di pannelli solari piani, finalizzata ad adottare gli accorgimenti necessari alla sua attenuazione o alla sua completa eliminazione. Lo studio è condotto su pannelli a tubi trasparenti attraverso analisi ottica. In una fase iniziale si è realizzato un pannello solare piano a tubi trasparenti, con le dimensioni di un classico pannello disponibile in commercio, all’interno del quale si è fatto fluire un nanofluido a base di acqua e ossido di alluminio (Al2O3). Le zone interessate dalla sedimentazione della fase solida erano il tubo collettore di ingresso, quello collettore di uscita e i tubi traversi La quantità di fase solida depositata è risultata essere dipendente dalla velocità del nanofluido nei tubi di ingresso e di uscita. Nella fase successiva si è realizzato un pannello solare piano, delle stesse dimensioni del precedente, con una modifica sui tubi di ingresso e di uscita, volta a eliminare il fenomeno della sedimentazione per effetto di una opportuna variazione di velocità del nanofluido. La forma era tale da garantire una velocità costante lungo tutta la loro lunghezza. Essa è stata ottenuta agendo sulla sezione di passaggio all’interno dei tubi attraverso l’introduzione di un solido opportunamente sagomato. Il nanofluido utilizzato era a base di acqua e Al2O3 ed era alimentato nelle stesse condizioni adottate per il pannello della prima fase. Per effetto delle modifiche apportate il fenomeno di sedimentazione si è ridotto a livelli trascurabili e, in certi punti, è stato completamente eliminato. Il pannello solare modificato, dotato di tubi a sezione variabile, è stato oggetto di domanda di brevetto per invenzione industriale depositata all’Ufficio Italiano Brevetti e Marchi (N° LE2010A000006) e successivamente è stata depositata anche la domanda di brevetto internazionale (Application number: PCT/IB2011/051988).

Le pompe di calore geotermiche hanno avuto in Italia nell’ultimo decennio sviluppo e diffusione grazie soprattutto al fatto che consentono consistenti risparmi energetici quando utilizzate per soddisfare il fabbisogno di climatizzazione estiva e invernale degli edifici. In questo lavoro vengono analizzati i diversi modelli matematici presenti in letteratura per il calcolo delle prestazioni delle pompe di calore dotate di scambiatori orizzontali e verticali e per le relative metodologie di dimensionamento semplificate. A seguito dei risultati di questa analisi è stato concepito e implementato un modello matematico in ambiente Matlab-Simulink che integra le metodologie per la progettazione dei sistemi geotermici verticali e orizzontali e valuta le potenze termiche scambiate con il terreno correggendo i valori tabellari di riferimento e largamente in uso nella progettazione semplificata degli impianti di piccola taglia, in funzione delle particolari condizioni operative. Il modello è tarato con il riferimento a risultati sperimentali e ai valori in uscita dalle procedure di calcolo del software RETScreen.