Impact of exterior convective heat transfer coefficient models on the energy demand prediction of buildings with different geometry

Abstract

Accurate models for exterior convective heat transfer coefficients (CHTC) are important for predicting building energy demand. A detailed review of the literature indicates that existing CHTC models take into account the impact of building geometry either incompletely, or not at all. To the best of our knowledge, research on the impact of exterior CHTC models on the predicted energy performance of buildings with different geometry has not yet been performed. This paper, therefore, investigates the influence of CHTC models on the calculated energy demand of buildings with varying geometry. Building energy simulations are performed for three groups: buildings with Hb (building height) > Wb (building width), buildings with Hb < Wb and buildings with Hb = Wb. Six commonly used CHTC models and a new generalized CHTC model are considered. The generalized CHTC model is expressed as a function of Hb and Wb. The simulations are performed for low and high thermal resistances of the building envelope. The results show that the different CHTC models provide significantly different predictions for the building energy demand. While for annual heating demand, deviations of −14.5% are found, for the annual cooling demand a maximum deviation of +42.0% is obtained, compared to the generalized CHTC model. This study underlines the need for the CHTC models to consider building geometry in their expressions, especially for high-rise buildings. For low-rise builgings, the observed deviations between the existing and the generalized CHTC model are less pronounced.

A physics-based high-resolution BIPV model for building performance simulations

“…Another important aspect that deserves further attention is the influence of the wind flow on the heat dissipation conditions in BIPV elements. As research on wind flow in the built environment progresses, new insights on how the wind affects the convective heat dissipation in buildings have been published (Emmel et al, 2007;Defraeye et al, 2011;Mirsadeghi et al, 2013;Montazeri et al, 2015;Montazeri & Blocken, 2017Iousef et al, 2019). In particular, it has been demonstrated that convective heat transfer coefficients resulting from wind effects not only vary over the building surfaces, but also depend on the building geometry (Montazeri et al, 2015;Montazeri & Blocken, 2017).…”

Numerical analysis of the performance of green façades

“…As mentioned in (Susorova et al, 2013), some studies showed a decrease in values of convective heat transfer coefficients for a wide range of vegetated façade types, the present findings through the (Ayata et al, 2011; ASHRAE, 2020) methods are in accordance with this trend. It is known that the building geometry, surroundings and wind directions have a significant effect on the magnitude of the convective heat transfer coefficient (Defraeye et al, 2011;Iousef et al, 2019). Several correlations are based on the results of flat plate experiments in wind tunnels (Jayamaha et al, 1996) and may not fully capture the local variations of geometry and wind directions around the building façades.…”

Bina cepheleri pencere/duvar oranı ve pencere özelliklerinin enerji performansına etkisi

“…Bu kayıp ve kazançlar bina cephe elemanlarının özellikleri ile doğrudan ilişkilidir. Bina cephesi, bina enerji verimliliği ve iç termal konfor ihtiyacının karşılamasında çok önemli bir rol oynamaktadır [10,11]. Bina cephesi, iç-dış ortamlar arasında karmaşık bir arayüzdür [11].…”

“…Bina cephesi, bina enerji verimliliği ve iç termal konfor ihtiyacının karşılamasında çok önemli bir rol oynamaktadır [10,11]. Bina cephesi, iç-dış ortamlar arasında karmaşık bir arayüzdür [11]. Bina kabuğunu meydana getiren pencere-duvar oranı, insan deneyimini çeşitli şekillerde etkileyen bir tasarım özelliğidir [12].…”