A Comprehensive Review of Natural Convection in Triangular Enclosures

Kamiyo, O. M.; Angeli, Diego; Barozzi, Giovanni Sebastiano; Collins, Michael W.; Olunloyo, V. O. S.; Talabi, S.O.

doi:10.1115/1.4004290

Cited by 55 publications

(22 citation statements)

References 51 publications

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“…In the first category, sealed attic configuration is considered, and the problem is usually represented by natural convection in triangular enclosures. As reviewed by Kamiyo et al [5] and by Saha and Khan [6], a considerable number of experimental and numerical studies in this category (e.g., [7][8][9][10][11][12][13][14][15][16]) have been devoted to the analysis of flow and heat transfer under laminar conditions, while only a few studies (e.g., [17,18]) investigated turbulent flow and heat transfer, although the air flow in real residential attics is almost always turbulent.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Wang

Shen

2012

Energies

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Abstract:The impacts of ventilation ratio and vent balance on cooling load and air flow of naturally ventilated attics are studied in this paper using an unsteady computational fluid dynamics (CFD) model. Buoyancy-driven turbulent ventilations in attics of gable-roof residential buildings are simulated for typical summer conditions. Ventilation ratios from 1/400 to 1/25 combined with both balanced and unbalanced vent configurations are investigated. The modeling results show that the air flows in the attics are steady and exhibit a general streamline pattern that is qualitatively insensitive to the variations in ventilation ratio and vent configuration. The predicted temperature fields are characterized by thermal stratification, except for the soffit regions. It is demonstrated that an increase in ventilation ratio will reduce attic cooling load. Compared with unbalanced vent configurations, balanced attic ventilation is shown to be the optimal solution in both maximizing ventilating flow rate and minimizing cooling load for attics with ventilation ratio lower than 1/100. For attics with ventilation ratios greater than 1/67, a configuration of large ridge vent with small soffit vent favors ventilating air flow enhancement, while a configuration of small ridge vent with large soffit vent results in the lowest cooling energy consumption.

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Section: Introductionmentioning

confidence: 99%

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Wang

Shen

2012

Energies

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“…The majority of the existing literature on attic energy performance concerned with sealed attics, as reviewed by Kamiyo et al [2] and by Saha and Khan [3], while only a few publications reported studies involving attic ventilation. For example, Medina et al [4,5] proposed a correlation-based mathematical model for vented residential attics and compared model predictions with experimental data, and Moujaes and Alsaiegh [6] employed a finite element model to simulate the thermal effects of placing a radiant barrier system inside a vented residential attic for a case study under summer weather conditions.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Roof Pitch and Ceiling Insulation on Cooling Load of Naturally-Ventilated Attics

Wang

Shen

2012

Energies

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A 2D unsteady computational fluid dynamics (CFD) model is employed to simulate buoyancy-driven turbulent ventilation in attics with different pitch values and ceiling insulation levels under summer conditions. The impacts of roof pitch and ceiling insulation on the cooling load of gable-roof residential buildings are investigated based on the simulation of turbulent air flow and natural convection heat transfer in attic spaces with roof pitches from 3/12 to 18/12 combined with ceiling insulation levels from R-1.2 to R-40. The modeling results show that the air flows in the attics are steady and exhibit a general streamline pattern that is qualitatively insensitive to the investigated variations of roof pitch and ceiling insulation. Furthermore, it is predicted that the ceiling insulation plays a control role on the attic cooling load and that an increase of roof pitch from 3/12 to 8/12 results in a decrease in the cooling load by around 9% in the investigated cases. The results suggest that the increase of roof pitch alone, without changing other design parameters, has limited impact on attics cooling load and airflow pattern. The research results also suggest both the predicted ventilating mass flow rate and attic cooling load can be satisfactorily correlated by simple relationships in terms of appropriately defined Rayleigh and Nusselt numbers.

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“…It was observed that, for winter conditions and at small pitch angles, increasing Ra resulted into a multicellular flow structure. Further review on this subject can be found in Kamiyo et al [7].…”

Section: Figure 1 Physical Modelmentioning

confidence: 99%

Natural convection in asymmetric triangular enclosures heated from below

Kamiyo

Angeli

Barozzi

et al. 2014

J. Phys.: Conf. Ser.

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. Among a number of scientific topics he cultivated in his brilliant academic career, convection heat transfer was the first and the most beloved.Abstract. Triangular enclosures are typical configurations of attic spaces found in residential as well as industrial pitched-roof buildings. Natural convection in triangular rooftops has received considerable attention over the years, mainly on right-angled and isosceles enclosures. In this paper, a finite volume CFD package is employed to study the laminar air flow and temperature distribution in asymmetric rooftop-shaped triangular enclosures when heated isothermally from the base wall, for aspect ratios (AR) 0.2 ≤ AR ≤ 1.0, and Rayleigh number (Ra) values 8 × 10 5 ≤ Ra ≤ 5 × 10 7 . The effects of Rayleigh number and pitch angle on the flow structure and temperature distributions within the enclosure are analysed. Results indicate that, at low pitch angle, the heat transfer between the cold inclined and the hot base walls is very high, resulting in a multi-cellular flow structure. As the pitch angle increases, however, the number of cells reduces, and the total heat transfer rate progressively reduces, even if the Rayleigh number, being based on the enclosure height, rapidly increases. Physical reasons for the above effect are inspected.

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A Comprehensive Review of Natural Convection in Triangular Enclosures

Cited by 55 publications

References 51 publications

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

The Impact of Roof Pitch and Ceiling Insulation on Cooling Load of Naturally-Ventilated Attics

Natural convection in asymmetric triangular enclosures heated from below

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