Local heat transfer around a wall-mounted cube in the turbulent boundary layer

Nakamura, Hajime; Igarashi, Tamotsu; Tsutsui, Takayuki

doi:10.1016/s0017-9310(01)00009-6

Cited by 89 publications

(50 citation statements)

References 10 publications

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“…Empirical CHTC correlations for external urban surfaces have been evaluated using field measurements [25e30] and wind tunnel experiments [18], [22,31]. However, due to wind direction variability and complex canopy roughness especially in field experiments, the flow field and therefore the CHTC are very sensitive to the boundary conditions and inconsistencies between measurement campaigns were found [32e34].…”

Section: Introductionmentioning

confidence: 99%

Realistic solar heating in urban areas: Air exchange and street-canyon ventilation

Nazarian

Kleissl

2016

Building and Environment

105

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a b s t r a c tNumerical fluid flow and heat transfer simulations of a three-dimensional idealized urban environment are performed to investigate the effect of realistic non-uniform thermal forcing that is caused by solar insolation and inter-building shadowing. Simulations at different times of day are performed using Large Eddy Simulation (LES) and mean flow and turbulence statistics are investigated as determinants for urban canyon ventilation. The differential surface heating of the building canyon is parameterized using sets of horizontal and vertical Richardson numbers indicating atmospheric instability and solar tilt with respect to the wind direction, respectively. Roof heating, in combination with building walls and ground heating, is shown to be important in the strength and location of the canyon vortex. For example, in case of weak vertical stratification (Ri v ) and high horizontal temperature gradient opposing the wind direction above the canyon (Ri h ), the combination of roof heating and ground heating decreases the strength of the canyon vortex. The distribution of local convective heat transfer coefficients (CHTC) on building facets are analyzed. Throughout the day, the windward walls exhibit larger CHTCs and leeward heating enhances CHTC from the roof and windward walls. Additionally, the wall heating in the cross-stream canyon (north-south in our case) enhances the air exchange rate from the canyon, especially when the leeward wall is heated.

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Section: Introductionmentioning

confidence: 99%

Realistic solar heating in urban areas: Air exchange and street-canyon ventilation

Nazarian

Kleissl

2016

Building and Environment

105

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“…Section 2 describes the numerical model used in the numerical simulations. In Section 3 a comparison between convective heat transfer coefficient values on the windward and leeward façade within an urban canyon and on the windward external façade given by our simulations and the CHTC given by experimental correlation [19,[20][21][22][23][24][25][26][27] and by numerical simulations by other authors [21] is carried out.…”

Section: Open Accessmentioning

confidence: 99%

CFD Analysis of Convective Heat Transfer Coefficient on External Surfaces of Buildings

2015

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Convective heat transfer coefficients for external building surfaces are essential in building energy simulation (BES) to calculate convective heat gains and losses from building facades and roofs to the environment. These coefficients are complex functions of: building geometry, building surroundings, local air flow patterns and temperature differences. A microclimatic analysis in a typical urban configuration, has been carried out using Ansys Fluent Version 14.0, an urban street canyon, with a given H/W ratio, has been considered to simulate a three-dimensional flow field and to calculate the thermal fluid dynamics parameters that characterize the street canyon. In this paper, the convective heat transfer coefficient values on the windward external façade of the canyon and on the windward and leeward inner walls are analyzed and a comparison with values from experimental and numerical correlations is carried out.

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“…A significant amount of research has been performed by wind-tunnel experiments of convective heat transfer of isolated bluff bodies, mostly cubes, placed in a turbulent boundary layer [16,[34][35][36][37][38][39][40][41][42]. In contrast to full-scale experiments, detailed information of the distribution of the CHTC over each surface, its relation with the flow field and the dependency on flow direction was provided.…”

Section: Wind-tunnel Experimentsmentioning

confidence: 99%

Convective heat transfer coefficients for exterior building surfaces: Existing correlations and CFD modelling

Defraeye

Blocken

Carmeliet

2011

Energy Conversion and Management

211

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Convective heat transfer at exterior building surfaces has an impact on the design and performance of building components such as double-skin facades, solar collectors, solar chimneys, ventilated photovoltaic arrays, etc. and also affects the thermal climate and cooling load in urban areas. In this study, an overview is given of existing correlations of the exterior convective heat transfer coefficient (CHTC) with the wind speed, indicating significant differences between these correlations. As an alternative to using existing correlations, the applicability of CFD to obtain forced CHTC correlations is evaluated, by considering a cubic building in an atmospheric boundary layer. Steady Reynolds-Averaged Navier-Stokes simulations are performed and, instead of the commonly used wall functions, low-Reynolds number modelling (LRNM) is used to model the boundary-layer region for reasons of improved accuracy. The flow field is found to become quasi independent of the Reynolds number at Reynolds numbers of about 10 5 . This allows limiting the wind speed at which the CHTC is evaluated and thus the grid resolution in the near-wall region, which significantly reduces the computational expense. The distribution of the power-law CHTC-U 10 correlation over the windward and leeward surfaces is presented (U 10 = reference wind speed at 10 m height). It is shown that these correlations can be accurately determined by simulations with relatively low wind speed values, which avoids the use of excessively fine grids for LRNM, and by using only two or three discrete wind speed values, which limits the required number of CFD simulations.

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Local heat transfer around a wall-mounted cube in the turbulent boundary layer

Cited by 89 publications

References 10 publications

Realistic solar heating in urban areas: Air exchange and street-canyon ventilation

Realistic solar heating in urban areas: Air exchange and street-canyon ventilation

CFD Analysis of Convective Heat Transfer Coefficient on External Surfaces of Buildings

Convective heat transfer coefficients for exterior building surfaces: Existing correlations and CFD modelling

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