Thermal characterization of a multilayer coating for seismic and energy building renovation

Many buildings built in Italy in the 60s and 70s need an energy requalification and at the same time an improvement of the seismic behaviour. A non-invasive method for a joint requalification consists of an anti-seismic plaster layer and a thermal coating. In this work, a multi-layer package of 3 cm of SFRM coating and 8 cm of wood fiber placed on a 20 cm masonry wall is analyzed. Numerical and experimental analysis allowed to characterize the wall, and to determine the influence of the connecting elements

Analysis of the temperatures measured in very thick and insulating roofs in the vicinity of a chimney

Chimneys convey exhaust gas produced in domestic heat appliances to the external environment and to do this they have to pass through elements such as roofs and floors. If these elements are made up of flammable materials the fire hazard may occur. In some European countries the number of roof fire is very high and they affect also certified chimneys, that is, tested following the prescription of the related standards. The aim of this paper is to highlight that the certification procedure does not allow to test chimneys in the worst condition, therefore, chimney installed following the manufacturer prescriptions may in some cases cause the overheating and subsequent roof fire. To do this, experimental tests have been performed for measuring the temperature on roofs in the vicinity of a certified chimney. The results show that the certification procedure should be revised

Performance analysis of a large TES system connected to a district heating network in Northern Italy

The addition of storage capacity to district heating systems increases flexibility and expands the range of usable heat sources. Despite their apparently simple nature, thermal energy storage (TES) tanks display a wide range of performances due to different construction and operation choices, as proven by numerous literature studies. However, most of the investigations focus on domestic-size tanks of few cubic metres or, on the other hand, very large seasonal storages of hundreds of thousands of cubic metres. In this work, the performances of a 5000 m3 TES recently introduced in a district heating network in Brescia, Italy, are experimentally analysed using temperature and flow rate measurements acquired over two months in the heating season. First-law efficiencies, exergy, and stratification parameters are calculated and discussed. Energy and exergy efficiencies computed for all examined cycles are above 90%, in line with literature values for smaller and larger TESs. The thermocline profile is generally stable through the cycle unless anomalous events occur, and its average thickness is below 4% of the water height. The combined analysis of single-point indicators, thermocline profiles, and qualitative temperature heatmaps shows that short partial charge/discharge events followed by long stand-by periods negatively affect performances. Stratification efficiency and stratification number give further time-dependent information on the vertical distribution of temperatures in the TES. Heat losses towards the outside are also estimated and discussed in the light of integrative measurements performed on other TESs with similar characteristics, showing that particular care must be paid to the top, where dissipation could be increased by evaporation phenomena if the water surface is not protected

Design of a 5th Generation District Heating Substation Prototype for a Real Case Study

The evolution of district heating networks is moving toward low temperatures in heat distribution with so called 4th generation networks. However, the lowest heat transfer fluid temperatures in district heating are achieved through ultra-low temperature networks, referred to as 5th generation district heating networks (5GDHNs). Low temperatures in heat distribution results in an extremely different configuration of 5GDHN compared to traditional district heating network, especially in the grid substation due to the inability to directly couple the grid with the buildings. This paper presents a detailed design of a 5th generation substation prototype, which is carried out to verify the proper operation and monitor the performance of this type of substation in a real case study. The prototype is fed by low-temperature waste heat, currently dissipated through evaporative towers, and will be built in the city of Brescia, Italy. The layout of the substation prototype, consisting of a bidirectional pumping system, a reversible water-to-water heat pump, an inertial thermal energy storage and a heat exchanger, is presented. An analysis is performed to figure out which refrigerant offers the best performance of the heat pump. In addition, fixed the refrigerant, the performance of the grid connected heat pump is found to be increased from 29.5% to 55.5% for both heating and cooling compared with a stand-alone air-to-water heat pump solution. Finally, the process flow diagram and the piping and instrumentation diagram of the substation are presented and commented

Numerical and experimental study on metamaterials featuring acoustical and thermal properties

Metamaterials can be defined as materials which, for their peculiar composition or structure, exhibit characteristics that are not normally found in nature. "Multifunctional" metamaterials could be used to optimise different characteristics at the same time. In this paper the authors try to apply them for thermal and acoustic optimization of external building walls. Thermal optimization consists in obtaining a low transmittance, important in winter, and a low periodic thermal transmittance, important in summer. Acoustic optimization consists in obtaining high sound transmission loss, to respect the law prescriptions, and a good sound absorption coefficient, if possible. In this way should be possible enhance the comfort conditions in buildings and reduce the energy demand for winter heating and summer cooling. The proposed solution consists of several layers with different suitable characteristics: the sequence of the layers has been chosen with particular care. The thermal analysis has been performed by means of a self-developed code based on the ISO 13786 standard. The acoustic behaviour of the single layers has been determined following the procedure given by the ASTM E2611-09 standard using a four-microphone impedance tube and the transfer matrix method has been used for the complete assembly. This preliminary combined study showed encouraging results

Conversion of end-of-life household materials into building insulating low-cost solutions for the development of vulnerable contexts: Review and outlook towards a circular and sustainable economy

In a world increasingly aware of the environmental cost of the current production/ consumption model, the use of sustainable practices to reduce our environmental impact as a society becomes imperative. One way to reduce this impact is to increase the reuse of materials that are considered, by current definitions of ”waste”, at their end of life. End-of-Life Household Materials (EoLHM) can be defined as household waste materials that still possess exploitable properties, thus making them suitable for reuse. There are several studies in the literature that address the recycling of these materials. When it comes to their reuse, unfortunately, only a limited number of studies are available. This paper aims to fill this gap by investigating the possibility to convert EoLHM, such as clothes or packaging, into low-cost thermal insulating materials for the improvement of the indoor thermal comfort in buildings, especially for households at risk of suffering from energy poverty. For this purpose, a comprehensive literature review and a qualitative analysis of both commercial and EoLHM are proposed. Commercial thermal insulating materials analysis is used as a reference to measure the performance of EoLHM. Important aspects to be considered when choosing suitable EoLHM for a smart conversion and reuse are also investigated. The most important outcome of this investigation is the comprehension that the conversion of EoLHM into insulating material is possible, and it implies a direct reduction in waste production, with environmental benefits and positive social implications. However, some aspects such as adaptability, life expectancy, collection and storage are, at present, in need of further thinking and development to make the EoLHM reuse and re-conversion processes viable on a large (neighborhood/city) scale

Sustainable and low-cost solutions for thermal and acoustic refurbishment of old buildings

This paper investigates the possibility to realize solutions for buildings thermal and acoustic refurbishment by using end-of-life household materials, such as cardboard, clothes, and egg-boxes. These solutions can be installed to improve the indoor quality in neighborhoods populated by people below the poverty threshold. The considered end-of-life household materials and their combination have been analyzed from the acoustic and thermal points of view. First of all, the sound insulation and the sound absorption properties have been determined by means of an impedance tube. Then, the summer and the winter thermal performances, when coupled to different wall systems, have been investigated analitically. The results suggest that good thermal and acoustic characteristics can be achieved in a contained thickness by coupling end-of-life household materials

Proposta di metodi non invasivi per la misura delle proprietà termiche delle pareti di un edificio

In questa memoria vengono proposti alcuni metodi per determinare le proprietà termiche di una parete, adatti ad essere utilizzati su edifici esistenti ed eventualmente già abitati. Essi infatti richiedono di misurare unicamente la temperatura e il flusso termico specifico sulle due superfici della parete e la temperatura dell'aria all'interno e all'esterno dell'edificio, non danneggiando in alcun modo la parete stessa. Il modello sviluppato per la resistenza termica è valido in un transitorio qualsiasi, purché le temperature varino lentamente rispetto al tempo caratteristico della parete. Per la capacità termica vengono presentati due modelli, il primo valido in regime periodico, il secondo in un transitorio qualsiasi: entrambi richiedono la conoscenza della resistenza termica. La validità dei modelli è stata sottoposta ad una prima verifica che utilizza come dati in ingresso i risultati di alcune simulazioni numeriche eseguite con il codice Fluent su pareti aventi diversi tempi caratteristici. Sulla superficie esterna si è imposto un flusso termico con andamento sinusoidale, sulla superficie interna scambio termico convettivo con aria a temperatuta costante con coefficiente di scambio termico convettivo anch'esso costante. I modelli si sono dimostrati corretti, anche se presentano alcuni limiti e difficoltà di applicazione

Effect of test conditions on the experimental determination of thermal conductivity of walls by means of heat flow meters

The use of heat flow-meters to measure thermal conductivity of walls has a larger margin of error compared with other laboratory tests. The aim of this work is to investigate which variables can influence the measurement results. Computational simulations are elaborated, changing the heat transfer coefficients on surfaces, the thermal conductivity and the thickness of walls, the configuration of probes on the wall. The results of the simulations are collected in tables containing the errors on thermal conductivity values due to different factors. Moreover, experimental tests are done on a wall specimen following indications of simulations results. This work shows computational and experimental results