Horizontal heat impacts of a bare facade on air temperature in an adjacent green plot within pedestrian heights in Beijing

Self Cite

Thermal condition of the surface soil layer was neglected due to much concern of the urban heat island effect, which has an important impact on cities. In this study, on-site measurements of surface soil layer temperatures were conducted between two east-west oriented buildings in the winter, spring and summer. Building shade was shown to reduce average surface soil layer temperatures to 0.33, 0.33 and 0.37°C in three seasons, respectively. The horizontal heat flux between the building and the soil was calculated and showed different intensities at various monitoring sites. Additionally, the building shade could reduce and stabilize the surface soil layer temperature. According to the analytic hierarchy process, among six energy factors only horizontal heat flux between the building and the soil was correlated significantly ( p <0.05) to the different surface soil layer temperatures. This has a key or dominant role in affecting the difference in surface soil layer temperatures, which was influenced by the building shade. Moreover, the soil warming rate was reduced by the building shade (50% at most). The surface soil layer temperatures at various observation points were compared with the air temperature. The surface soil layer was found to have different roles between two sites in three seasons.

Section: Abnormality On Diurnal Changes Of Surface Soil Layer Tempera...mentioning

confidence: 74%

Horizontal heat impacts and shading effects of buildings on surface soil layer in Beijing, China

Zhou

Yan

et al. 2022

Self Cite

“…Replacement of the sky temperature T sky and the sky emissivity ε sky by the temperature T a and emissivity ε a of the atmosphere near the ground seems to be logical, since the major portion of long-wave radiation of the sky originates from the air environment not too far from the ground. The emissivity values ε a are inferred from the correlation function (2), as given by equation ( 3)…”

Section: Thermal Models Of the Skymentioning

confidence: 99%

“…that usually fits well with the interval ε a 2 ð0; 1Þ, which is a correct numerical range of thermal emissivity. This is another fact that advocates the choice of the correlation function (2). No wonder that some authors 13 tried to derive this emissivity directly from the emissive properties of water vapour and carbon dioxide contained in the atmosphere near the ground.…”

Section: Thermal Models Of the Skymentioning

confidence: 99%

See 1 more Smart Citation

Are the local sky temperature models and the global thermal standard model EN ISO 6946(2017) numerically compatible?

Ficker

2023

Local sky temperature models are often used by researchers to improve the estimation of building heat losses. Besides the local sky temperature models, there is a global temperature model implemented in EN ISO 6946(2017) that may also produce reasonable results if it is conveniently applied. To assess the competitiveness of global and local models, it is desirable to perform a direct numerical comparison of their results. Such a comparison has not been published so far. This study aims to analyze the computational differences between three models of sky temperature, namely, the Swinbank model, the universal model and the standard model implemented in EN ISO 6946(2017). The study verifies the robustness of the global thermal standard model to account for the acting of the cold sky on building envelopes compared to local sky models specially designed for this purpose. The quasi-nocturnal conditions are supposed to reveal the main features of the long-wave infrared interactions between the building facade and the sky. The study has proved the capability of the global standard model to successively compete with the local sky temperature models at least within the conditions of the quasi-nocturnal environment.

“…This analysis has allowed for a discussion on the thermal energy performance of external walls utilizing special insulating materials. Zhou, Wang, Hu and Sun 10 have discussed the effect of the horizontal heat impact of facades on the surrounding atmospheric environment at pedestrian heights. The heat flux from the investigated facade proved to be almost homogeneous.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of heat losses of building walls containing reflective foils

Ficker

2022

In external building walls, air cavities are occasionally used to reduce heat losses. Closed air cavities improve the thermal resistance of building structures, especially when the inner surfaces of the cavities are covered with low-emissivity materials such as metalized foils. With these structures, the problem of accurate determination of radiative heat arises. In this contribution, radiative heat transfer is determined by the precise algebraic radiosity method, so far not applied in the field of thermal building technology. Radiative heat computed by the radiosity method has been coupled with convective heat evaluated by the correlation functions of the Nusselt numbers. The combined radiative-convective heat transfer through a sandwich wall containing an air cavity with metalized surfaces (aluminium foils) has been analysed. A computer program has been developed to quantify the real insulation effect of reflective aluminium foils. The sandwich building structure has been subjected to real one-month winter conditions as defined by official meteorological data valid for the city of Brno. The software is based on an iterative procedure that solves the combined radiative-convective steady heat transfers by means of one-day average temperatures and wind speeds. Various arrangements of foils in the cavity have been explored to achieve the maximum value of thermal resistance. The corresponding heat savings have been quantified. The best configuration of foils in the cavity has been found to ensure maximum thermal savings. The insulation system that uses foils has been compared to the system that uses mineral wool. The comparison was based on economic considerations.