New external convective heat transfer coefficient correlations for isolated low-rise buildings

Emmel, M.; Abadie, Marc; Mendes, Nathan

doi:10.1016/j.enbuild.2006.08.001

Cited by 133 publications

(51 citation statements)

References 9 publications

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“…Anyway, as Palyvos says in his study, in this field many uncertainties still exist and many questions are still open [15], above all for very low air speeds and surface-to-air temperature differences [16]. Additional studies are now ongoing on a full scale experimental building in order to refine the convective heat transfer coefficient for the U measurement of external walls on site.…”

Section: Calculation Of Convective Coefficientmentioning

confidence: 99%

Infrared Screening of Residential Buildings for Energy Audit Purposes: Results of a Field Test

2013

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Abstract:In the European Union (EU), the building sector is responsible for approximately 40% of total energy consumption. The existing building stock is inefficient and can, and indeed must be retrofitted to address this issue. The practical implementation of the European strategies requires knowledge of the energy performance of existing buildings through energy audit techniques. Application of thermography in the fields of energy are very widespread, since, through such a non-invasive investigation, and through correct interpretation of infrared images, it is possible to highlight inefficiencies in buildings and related facilities. The paper shows and discusses the results of an infrared audit campaign on 14 existing buildings located in Milan Province (Italy) made in different construction periods and characterised, therefore, by different building technologies. The U-values obtained in an indirect way through the thermography of the opaque walls of the buildings investigated, were compared with the actual known values in order to verify the reliability of the method and the possible margin of error. The study indicated that the category of buildings in which the application of this method is sufficiently reliable is that of solid-mass structure buildings, the most widespread in Italy, whereas in the case of buildings whose external walls are insulated, the percentage of deviation is very high.

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Section: Calculation Of Convective Coefficientmentioning

confidence: 99%

Infrared Screening of Residential Buildings for Energy Audit Purposes: Results of a Field Test

2013

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“…The previous studies used the steady Reynolds-Averaged Navier-Stokes (RANS) equations to model the flow and the temperature field, combined with wall functions [46] or low-Reynolds number modelling (LRNM) [47,48] for boundary-layer modelling. Steady RANS however generally leads to less accurate flow predictions around bluff bodies, in zones of separation and recirculation [49][50][51][52][53], compared to unsteady RANS or Large-Eddy simulations, due to steady-flow and turbulence modelling.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, Computational Fluid Dynamics was used to predict convective heat transfer at exterior building surfaces [46][47][48]. The main advantages of CFD for this application are that: (1) a specific and complex building or building configuration can be analysed; (2) very high spatial resolution data are obtained; (3) high Reynolds number flows for atmospheric conditions (10 5 - 10 7 ) can be considered and (4) detailed information on the flow field as well as the thermal field is available.…”

Section: Methodsmentioning

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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“…Roofs also have a greater view of the atmosphere than any vertical wall, so they will lose a much greater amount of heat to the atmosphere through infrared radiation. Convection strongly depends on wind direction; the convective heat loss coefficient is highest for upwind walls, followed by roofs, side walls and downwind walls, in that order [17,18].…”

Section: Optimal Thickness Of Thermal Insulationmentioning

confidence: 99%

The Effects of Roof and Wall Insulation on the Energy Costs of Low Income Housing in Mexico

2016

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Abstract:Environmental conditions, such as air temperature and solar radiation, have a complex relationship with the energy requirements for heating and cooling of residential buildings. In this work, a comparative analysis of the insulation methods most commonly applied to low income single-family houses in Mexico is presented, in order to find the most energy-efficient combinations of methods for the various climates in this country. A common kind of building, small houses built with hollow cinder block walls and concrete slab roofs, was analyzed considering three insulation scenarios: walls only, roof only and both. We used dynamic simulation to evaluate energy consumption under the climate conditions found in several Mexican cities. From the energy consumption data and the cost of electricity in Mexico, we calculated net annual energy costs, including both annual energy savings and the annualized cost of the initial investment in better insulation. Results of this analysis show that insulating both roof and walls is most effective in cities with cold winters; insulating just the roof is best for temperate climates; and insulating walls (combined with high-albedo roofs) is most effective for cities with year-long warm weather.

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New external convective heat transfer coefficient correlations for isolated low-rise buildings

Cited by 133 publications

References 9 publications

Infrared Screening of Residential Buildings for Energy Audit Purposes: Results of a Field Test

Infrared Screening of Residential Buildings for Energy Audit Purposes: Results of a Field Test

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

The Effects of Roof and Wall Insulation on the Energy Costs of Low Income Housing in Mexico

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