Search results for "thermal transmittance"

Long term energy efficiency study on different wall envelopes in Latvian climate conditions

2017

Abstract Five test stands have been built in Riga, Latvia equipped with sensors (temperature, solar radiation, humidity, etc.) to measure energy efficiency and thermal comfort conditions. Roof and floor constructions are made the same. For the walls building envelopes differ and typical materials used in Latvia (aerated concrete, ceramic building blocks, wooden log and plywood frame with rock wool insulation) are compared. Only rock wool is used for insulation to provide moisture transport through the construction. For study to be comparative thermal transmittance of all five test stands have been calculated equal (U=0.15…0.16 W/(m 2 ∙K)). The aim of research is to compare the integral calc…

Extraction of thermal characteristics of surrounding geological layers of a geothermal heat exchanger by 3D numerical simulations

2016

Ground thermal conductivity and borehole thermal resistance are key parameters for the design of closed Ground-Source Heat Pump (GSHP) systems. The standard method to determine these parameters is the Thermal Response Test (TRT). This test analyses the ground thermal response to a constant heat power injection or extraction by measuring inlet and outlet temperatures of the fluid at the top of the borehole heat exchanger. These data are commonly evaluated by models considering the ground being homogeneous and isotropic. This approach estimates an effective ground thermal conductivity representing an average of the thermal conductivity of the different layers crossed by perforation. In order …

Il miglioramento energetico nel recupero degli edifici storici. Applicazione al patrimonio architettonico palermitano

L'architettura storica può assumere un ruolo rilevante nel raggiungimento degli obiettivi europei di efficienza energetica per il settore edile, obiettivi che, tuttavia, devono essere compatibili con la conservazione del patrimonio storico e del suo valore culturale. A tal fine è necessario far riferimento ai caratteri specifici dell'architettura storica e alla sua dimensione locale. La presente tesi, sulla base di tale assunto, esamina le prestazioni energetiche degli edifici storici e il loro potenziale miglioramento, concentrandosi sul patrimonio architettonico di Palermo, caso di studio significativo per l'area mediterranea. La ricerca, condotta con riferimento sia alla scala urbana sia…

Wall assemblies U-value calculation in test buildings using constant power heating

2018

Abstract Building envelopes under various climates behave differently, in this paper the actual thermal transmittance or U-value of five different wall assemblies are evaluated and compared with values, calculated using standard EN ISO 6946. The experiment is carried out in five test buildings with equal spatial orientation, the same ceiling and floor assemblies as well as the same windows and doors mounted in each building. The thermal transmittances for these partitions are assumed to be well known and therefore, by knowing temperature difference and heat sources inside the building, the thermal transmittance of wall assembly can be calculated. It is shown that for small buildings the cor…

Thermal Parameters Measurements of High-Rise Building Envelope

2016

In buildings, to ensure the thermal comfort of the occupants and to keep the energy consumption as low as possible, a correct design of the thermal system is necessary. To do so, an appropriate determination of the thermo-physical properties of the wall materials is needed, particularly; new light-weight building technologies are widely used in the construction of the building envelope. One of these parameters, particularly important in Mediterranean climatic dynamic conditions is the heat capacity, due to the presence of the sun’s energy contribution in hot and cold seasons. The value of the heat capacity in such like materials is typically quite different from the declared parameter, obta…

The thermophysical characterization of technical elements in the historic architecture: experiences in Palermo

2014

Per contemperare il miglioramento delle prestazioni energetiche e ambientali dell'architettura storica con l'esigenza della sua conservazione, è necessario analizzare le caratteristiche termofisiche dei materiali e degli elementi tecnici che la connotano. Tuttavia la disponibilità di pochi dati in merito si somma alle disomogeneità tipiche della costruzione storica e alle difficoltà di analisi ad esse connesse. In particolare, per la trasmittanza termica delle murature storiche, la letteratura scientifica evidenzia scostamenti anche notevoli tra i valori desunti da misure in situ e quelli calcolati, in genere superiori ai primi. Il contributo espone gli obiettivi e la metodologia di un prog…

Contributo alla conoscenza delle proprietà termofisiche delle murature storiche palermitane

2014

This paper presents the preliminary findings of in situ measurements of thermal transmittance taken in a monumental complex in Palermo. The objective of energy efficiency, one of the main aspects of sustainable construction, is now relevant also for historic architecture. The research aims at analysing the energy performance of the stone walls of the complex, characterized by various thickness, age and construction features. Measurements are taken in accordance with the international standard ISO 9869:1994. The U-values so obtained are compared with tabular data from the Italian standard UNI/TS 11300-1:2008 and with values calculated following the UNI EN ISO 6946:2008. Nine preliminary meas…

The thermal performances of historic masonry: In-situ measurements of thermal conductance on calcarenite stone walls in Palermo

2018

Abstract Rich literature explores materials and construction techniques of historic buildings, but limited information is available about the thermal and hygrometric features of their envelope. Nevertheless, accurate hygrothermal data are essential for identifying effective energy upgrade measures, which must be compatible with the conservation of the architectural heritage. In order to fill this gap, it is necessary to refer to local contexts, where the variety of historic buildings is limited and their material and construction features are comparable. This paper focuses on historic masonry walls and discusses the results of twenty in-situ measurements of thermal conductance, performed al…