Impact of external longwave radiation on optimum insulation thickness in Tunisian building roofs based on a dynamic analytical model
Impact of external longwave radiation on optimum insulation thickness in Tunisian building roofs based on a dynamic analytical model
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DOI：
10.1016/j.apenergy.2016.05.079
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发表时间：
2016-09
期刊：
影响因子：
11.2
通讯作者：
N. Daouas
中科院分区：
文献类型：
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作者：
N. Daouas
在突尼斯，建筑部门被视为能源消耗的一个主要问题。应特别注意提高建筑围护结构的热质量，并真实的考虑突尼斯的气候特点。最有效的措施之一是屋顶隔热。因此，本研究关注的是两种典型的屋顶结构和两种类型的绝缘材料的最佳绝缘厚度和由此产生的节能和投资回收期的确定。针对大气长波辐射与天空的非线性交换问题，提出了一种基于复有限傅立叶变换（CFFT）的解析动力学模型。该模型提供了一个计算时间短的解决方案，通过多层屋顶的瞬态传热，这可能是一个很好的替代一些数值方法。采暖和制冷年度负荷都经过严格估算，并用作生命周期成本分析的输入。在所研究的案例中，最经济的是中空的陶土基屋顶与岩棉绝缘，其中最佳的绝缘厚度估计为7.9厘米，投资回收期为6.06年，节能高达58.06%的能源消耗的成本没有绝缘。轻水堆交换组件的影响进行了量化，结果表明其重要的影响，每年的传输负载，因此，最佳绝缘厚度。敏感性分析表明，在突尼斯的气候背景下，冷却能源成本效益超过冬季处罚的冷屋顶的效率。CFFT的结果与那些sol-air度小时（DH）的比较表明，最佳的绝缘厚度和节能被高估，投资回收期被低估，使用后一种模式。建议CFFT模型可以是一个有效的工具，在不同的气候条件下的建筑围护结构构件的设计和能量分析。
In Tunisia, the building sector is considered as a major issue of energy consumption. A special attention should be drawn to improve the thermal quality of the building envelope with real consideration of the Tunisian climate specificity. One of the most effective measures is the roof insulation. Therefore, the present study is concerned with the determination of the optimum insulation thickness and the resulting energy savings and payback period for two typical roof structures and two types of insulation materials. An efficient analytical dynamic model based on the Complex Finite Fourier Transform (CFFT) is proposed and validated in order to handle the nonlinear longwave radiation (LWR) exchange with the sky. This model provides a short computational time solution of the transient heat transfer through multilayer roofs, which could be a good alternative to some numerical methods. Both heating and cooling annual loads are rigorously estimated and used as inputs to a life-cycle cost analysis. Among the studied cases, the most economical one is the hollow terracotta-based roof insulated with rock wool, where the optimum insulation thickness is estimated to be 7.9 cm, with a payback period of 6.06 years and energy savings up to 58.06% of the cost of energy consumed without insulation. The impact of the LWR exchange component is quantified and the results show its important effect on the annual transmission loads and, consequently, on optimum insulation thickness. A sensitivity analysis shows the efficiency of cool roofs in the Tunisian climate context, where the cooling energy cost benefits outweigh the wintertime penalty. Comparison of CFFT results with those of sol–air Degree-Hours (DH) shows that optimum insulation thickness and energy savings are overestimated and payback period is underestimated using the latter model. The proposed CFFT model could be an efficient tool for the design and the energy analysis of building envelope components in various climatic locations.