Browsing by Keyword "Thermal bridge"
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Item Calibration procedures for multidimensional heat transfer models based on on-site experimental data(2015-11-01) Garay, Roberto; Uriarte, Amaia; Apraiz, Inés; Martinez, Roberto Garay; Arrien, Amaia Uriarte; Egaña, Ines Apraiz; Tecnalia Research & Innovation; EDIFICACIÓN DE ENERGÍA POSITIVAAn experimental and numerical approach to the characterization of thermal bridges is presented, based on on-site taken measurements. Commonly on-site applied numerical thermal assessments perform one-dimensional heat transfer analysis over planar elements such as facades. However, it is well known that within thermal bridges in a building one-dimensional heat transfer analysis cannot be applied. A procedure is proposed, based on the creation of a numerical 2D thermal model which is calibrated against experimental data from several temperature and heat flux sensors which are located at specific points in the thermal bridge elements. Results of one particular implementation of this method are discussed.Item Disaggregation process for dynamic multidimensional heat flux in building simulation(2017-08-01) Garay, Roberto; Riverola, Alberto; Chemisana, Daniel; Martinez, Roberto Garay; Tecnalia Research & InnovationHeat transfer across envelopes (façade, roof, glazed areas) represents a big share of the energy flow within the heat balance of buildings. This paper focuses on areas of the envelope where multi-dimensional heat transfer occurs. These areas are commonly defined as thermal bridges, due to a localized reduction of thermal resistance of constructions in these places. This paper reviews common standardized methods to assess heat transfer in buildings, under various modelling assumptions: one-dimensional, multi-dimensional, steady state and dynamic. Within presently developed modelling and assessment methods, a need for improvement has been identified over existing methods for the thermal assessment of multi-dimensional heat transfer under dynamic conditions. A phasorial approach to differential heat transfer in thermal bridges has been developed, which serves as the dynamic extension of steady-state thermal bridge coefficients. This formulation is applied to the junction of a masonry wall with a concrete slab.Item Hybrid numerical and experimental performance assessment of structural thermal bridge retrofits(2018) Garay, Roberto; Garay Martinez, Roberto; Tecnalia Research & InnovationA methodological approach to the multi-dimensional heat transfer assessment of building envelopes is performed. The proposed method is particularly focused on thermally weak points in envelope-structure junctions and the assessment of envelope retrofit alternatives. Thermal performance in these spots is seldom assessed in energy audit processes, although it is one of the main heat loss paths in many insulated façade solutions. An envelope-slab junction case is presented, where multi-dimensional heat transfer occurs. The present paper proposes a methodology which allows for a hybrid experimental and numerical performance assessment in such circumstances. A numerical model is calibrated against experimental data, which is then modified to reflect various envelope retrofit solutions. Several possible analysis procedures are proposed, based on the capacities of transient thermal models.Item Performance assessment of thermal bridge elements into a full scale experimental study of a building façade(2014-12) Garay, Roberto; Uriarte, Amaia; Apraiz, Inés; Tecnalia Research & Innovation; EDIFICACIÓN DE ENERGÍA POSITIVAIn this paper, an experimental and numerical approach to the characterization of thermal bridges is presented. The need for this characterization was found within an experimental study in a 2 floor high facade. This facade was constructed with 3 concrete elements which were placed in it to produce a similar thermal bridge effect to the one created by floor slabs traditional building construction in Spain. Commonly applied thermal assessments perform one-dimensional heat transfer analysis over planar elements such as the facades studied in this experiment. However, it is well known that thermal bridges are locations in buildings where one-dimensional heat transfer analysis cannot be applied. This problem was approached by creating a numerical 2D thermal model which was calibrated against experimental data from several temperature and heat flux sensors which were located at specific points in the thermal bridge elements.