اثر شاخص های ناپایدار حرارتی جداره های ساختمانی بر میزان مصرف انرژی؛ بررسی موردی: خانه مسکونی در اقلیم گرم و خشک بیرجند (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
انتقال حرارت ازطریق جداره های ساختمان ها سهم زیادی در میزان مصرف انرژی دارند و عملکرد حرارتی آن ها در برقراری آسایش حرارتی فضاها مؤثر است. انتقال حرارت جداره ها به طور مستقیم بر میزان بار حرارتی ساختمان تأثیرگذار است. در این پژوهش تلاش شده که بتوان با تشخیص رفتار حرارتی مصالح در کاهش مصرف انرژی ازطریق جداره های خارجی، به عملکرد مطلوبی دست یافت. در شرایط ناپایدار حرارتی شاخص های متعددی چون ضریب انتشار حرارت، گرمای ویژه حجمی و ضریب سطح وجود دارند که با محاسبات، اثر هرکدام بر میزان مصرف انرژی ساختمان مورد بررسی قرار گرفت. نتایج پژوهش نشان داد که ضخامت مؤثرتر از نوع مصالح به کار رفته در جداره است. پذیرش حرارتی، ضریب سطح و زمان انتقال حرارت به هوای داخل، با ضخامت جداره ارتباط محسوسی ندارند. همچنین، با طراحی واحد مسکونی در اقلیم بیرجند، اثرات هریک از شاخص های ناپایدار حرارتی در میزان مصرف انرژی شبیه سازی شد. نتایج نشان داد که شاخص های ضریب انتشار حرارت، پذیرش حرارتی و گرمای ویژه حجمی، اثرات مستقیم و ضریب سطح، زمان تأخیر تابشی آن و زمان انتقال حرارت به هوای داخل اثرات معکوسی بر میزان مصرف انرژی سرمایش و گرمایش دارند. شاخص های ضریب کاهش و زمان تأخیر آن، اثر محسوسی بر مصرف انرژی ساختمان نداشته اند.The effect of non-steady state thermal indices of building walls on energy consumption; Case study: A residential house in hot and dry climate of Birjand
According to global primary energy consumption statistics, buildings significantly contribute to energy consumption, with an observed annual increase in this regard. As a consequence, buildings are responsible for greenhouse gas emissions and climate change. Therefore, it is essential to mitigate adverse environmental effects by reducing energy consumption. Heat transfer through the walls of buildings plays a crucial role in this context, and thermal performance significantly affects both energy consumption and the thermal comfort of indoor spaces. Since heat transfer through the walls is closely related to variations in indoor temperature, outdoor temperature, and the materials used in construction, it directly influences both cooling and heating loads. This study aims to achieve optimal performance by identifying the thermal behavior of materials to reduce energy consumption via external walls. Consequently, an understanding of the performance of materials in exterior walls is essential to measure their physical behavior in response to changes in outdoor temperature. To reduce energy consumption, two parameters—decrement factor and time lag—can create significant thermal inertia. However, there are many non-steady-state thermal indices, such as thermal transmittance, volumetric specific heat, and surface factor, and the impact of each on building energy consumption has been investigated through calculations. The non-steady-state thermal indices of walls depend on two important factors: material type and wall thickness. The study results indicate that wall thickness has a greater effect than the type of material used in the wall. The material type can lead to significant differences in the numerical values of indices such as volumetric specific heat, thermal admittance, thermal transmittance, time lag, and time lead. Increasing wall thickness reduces thermal indices such as thermal transmittance, decrement factor, and time lag (surface factor) while increasing the time lag (decrement factor). Thermal admittance, surface factor, and time lead show no significant relationship with wall thickness. Additionally, by designing a residential unit in the hot-dry climate of Birjand (Iran), the effects of each non-steady-state thermal index on energy consumption were simulated. The results indicated that indices such as thermal transmittance, thermal admittance, and volumetric specific heat have direct effects on cooling and heating energy consumption; an increase in these three parameters leads to higher cooling and heating energy consumption in buildings. Conversely, indices such as surface factor, time lag, and time lead negatively affect cooling and heating energy consumption, with their increase resulting in reduced annual energy consumption. However, the decrement factor and time lag have no significant effect on building energy consumption, with their correlations being weak and negligible. The annual energy consumption of buildings in this climate can be reduced by using materials with good thermal insulation properties. The simulation results indicate that the lowest annual heating and cooling energy consumption is associated with buildings constructed from AAC blocks, 3D concrete panels, and Perlite blocks. In contrast, the highest energy consumption occurs when using precast concrete, Liper blocks, or various types of clay bricks in the external walls.
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