Analysis of condensation and ventilation phenomena for double skin façade units

IF 1.8 4区工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Building Physics Pub Date : 2022-04-12 DOI:10.1177/17442591221084351

Francesco Squadroni, Giuseppe De Michele, E. Mazzucchelli, I. Demanega, S. Mangialardo, S. Avesani

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Abstract

This paper presents a study of the thermo-hygrometric behaviour of a Double Skin Façade (DSF) unit. The study aims (i) at comparing currently used calculation procedures according to European and American standards (UNI EN ISO 10077, UNI EN ISO 12631:2018, ISO 15099:2003, ANSI/NFRC 100 for the thermal performance and ISO 13788:2012 (2012) for the condensation risk), and (ii) at assessing the 2D hygrothermal performance of a double skin module through a Finite Element Method (FEM)-based model. According to the current standards, a detailed characterization of thermal and fluid dynamic phenomena in closed and ventilated cavities is neglected and a simplified approach is proposed, which tends to overestimate the overall U-value of the curtain wall (UCW) due to an incremental thermal resistance that depends on the thickness of the air gap layer and the level of ventilation. The potential risk of this simplification is that the DSF estimated design performance, whilst complying with regulatory requirements, present inconsistencies respect to the real behaviour, impacting energy, comfort, material degradation, etc. Accurate assessments could be done already during design through detailed FEM multi-physic analyses. Nevertheless, those require a specific knowledge, are cost and time-consuming. As a first step, this study focuses on comparing the normed calculation approach for the design, against a detailed FEM-based multi-physics methodology. Specifically, this couples CFD, hygrothermal and Ray Tracing physics in a tool for the calculation of thermal transmittance, g-value and relative humidity of a DSF with a customizable geometry. As a second step, given a real DSF unit that showed unforeseen phenomena of surface condensation inside the cavity during several hours in spring and autumn, the multi-physic tool has been used to evaluate the condensation risk with the current and modified DSF design, under static and time-dependent boundary conditions. Graphical abstract

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双层幕墙空调冷凝通风现象分析

本文介绍了一种双皮肤farade (DSF)装置的热湿特性的研究。该研究旨在(i)根据欧洲和美国标准(UNI EN ISO 10077、UNI EN ISO 12631:2018、ISO 15099:2003、ANSI/NFRC 100的热性能和ISO 13788:2012(2012)的冷凝风险)比较目前使用的计算程序，以及(ii)通过基于有限元法(FEM)的模型评估双蒙皮模块的二维湿热性能。根据目前的标准，忽略了封闭通风腔体中热和流体动力学现象的详细表征，并提出了一种简化的方法，该方法往往高估了幕墙(UCW)的总体u值，因为热阻增量取决于气隙层的厚度和通风水平。这种简化的潜在风险是，DSF估计的设计性能虽然符合法规要求，但与实际行为存在不一致，影响能源、舒适性、材料降解等。通过详细的有限元多物理场分析，在设计过程中就可以得到准确的评价。然而，这些需要特定的知识，成本高，耗时长。作为第一步，本研究的重点是比较设计的规范计算方法，与详细的基于有限元的多物理场方法。具体来说，它将CFD、湿热和光线追踪物理结合在一个工具中，用于计算具有可定制几何形状的DSF的热透射率、g值和相对湿度。第二步，给出了一个真实的DSF单元，该单元在春季和秋季的几个小时内显示了腔内不可预见的表面冷凝现象，在静态和时间相关的边界条件下，使用多物理场工具评估了当前和改进的DSF设计的冷凝风险。图形抽象

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Building Physics 工程技术-结构与建筑技术

CiteScore

5.10

自引率

15.00%

发文量

审稿时长

5.3 months

期刊介绍： Journal of Building Physics (J. Bldg. Phys) is an international, peer-reviewed journal that publishes a high quality research and state of the art “integrated” papers to promote scientifically thorough advancement of all the areas of non-structural performance of a building and particularly in heat, air, moisture transfer.