A laboratory experiment on natural ventilation through a roof cavity for reduction of solar heat gain

Susanti, Lusi; Homma, Hiroshi; Matsumoto, Hiroshi; Suzuki, Yasuyuki; Shimizu, Masayuki

doi:10.1016/j.enbuild.2008.06.016

Cited by 49 publications

(27 citation statements)

References 19 publications

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“…This could possibly be caused by a reflux of air at the outlet. The general increase in air temperature detected along the air cavity is in line with corresponding experimental measurements [27,[31][32][33][34].…”

Section: Temperature Profile Along the Cavitysupporting

confidence: 89%

“…However, the roof inclination and cavity height were kept constant during all measurements. The influence of inclination on the air velocity was investigated by Susanti et al [27], who observed that decreased inclination gave a reduction in velocity. The air velocity was also reduced when cavity temperatures decreased.…”

Section: Previous Researchmentioning

confidence: 99%

“…Experimental studies have also been performed to analyse thermal buoyancy in solar air collectors, by experiments on inclined channels heated from the top [27,[31][32][33][34]. Bunnag et al [33] observed that increased roof inclination decreased cavity temperatures significantly, while air velocity increased.…”

Section: Previous Researchmentioning

confidence: 99%

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Experimental Study of Thermal Buoyancy in the Cavity of Ventilated Roofs

et al. 2020

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Pitched wooden roofs are ventilated through an air cavity beneath the roofing in order to remove heat and moisture from the roof construction. The ventilation is driven by wind pressure and thermal buoyancy. This paper studies ventilation driven by thermal buoyancy in the air cavity of inclined roofs. The influence of air cavity design and roof inclination on the airflow is investigated. Laboratory measurements were carried out on an inclined full-scale roof model with an air cavity heated on one side in order to simulate solar radiation on a roof surface. Equipment to measure temperature was installed in the roof model, while air velocity in the cavity was determined by smoke tests. Combinations of different roof inclinations, air cavity heights and applied heating power on the air cavity top surface were examined. The study showed that increased air cavity height led to increased airflow and decreased surface temperatures in the air cavity. Increased roof inclination and heating power applied to the roofing also increased the airflow. The investigations imply that thermal buoyancy in the air cavity of pitched roofs could be a relevant driving force for cavity ventilation and important to consider when evaluating the heat and moisture performance of such a construction.

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Section: Temperature Profile Along the Cavitysupporting

confidence: 89%

Section: Previous Researchmentioning

confidence: 99%

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Experimental Study of Thermal Buoyancy in the Cavity of Ventilated Roofs

et al. 2020

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“…2) were derived from the literature study. From the literature, the suggested effective ratio of inlet area to outlet area is 1:1 [23,24], the effective solar collector tilt angle for Selangor, Malaysia is 10 [25] while the effective channel length of roof solar collector is 100 cm [7,26]. Thus, the overall dimensions for the developed roof solar collector were 1 m Â 1 m Â 0.2 m (length Â width Â cavity width), while the dimensions for the vertical stack were 1 m Â 1.95 m Â 0.2 m (width Â height Â cavity width).…”

Section: The Developed Prototype Devicementioning

confidence: 99%

Enhancement of stack ventilation in hot and humid climate using a combination of roof solar collector and vertical stack

Yusoff

Salleh

Adam

et al. 2010

Building and Environment

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a b s t r a c tIn the hot and humid climate, stack ventilation is inefficient due to small temperature difference between the inside and outside of naturally ventilated buildings. Hence, solar induced ventilation is a feasible alternative in enhancing the stack ventilation. This paper aims to investigate the effectiveness of a proposed solar induced ventilation strategy, which combines a roof solar collector and a vertical stack, in enhancing the stack ventilation performance in the hot and humid climate. The methodology selected for the investigation is physical experimental modelling which was carried out in the actual environment. The results are presented and discussed in terms of two performance variables: air temperature and air velocity. The findings indicate that the proposed strategy is able to enhance the stack ventilation, both in semi-clear sky and overcast sky conditions. The highest air temperature difference between the air inside the stack and the ambient air (T i ÀT o ) is achieved in the semi-clear sky condition, which is about 9.9 C (45.8 Ce35.9 C). Meanwhile, in the overcast sky condition, the highest air temperature difference (T i ÀT o ) is 6.2 C (39.3 Ce33.1 C). The experimental results also indicate good agreement with the theoretical results for the glass temperature, the air temperature in the roof solar collector's channel and the absorber temperature. The findings also show that wind has significant effect to the induced air velocity by the proposed strategy.

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“…In addition, the variation of wind velocity produces uncertainty in the relation with those temperature differences and the wind effect is excluded in this study. To enhance the buoyancy force and to increase the airflow rate, the tilt angle of the applied solar chimney was increased from a typical values of 20-30°to the tilt angle of 45°6 , 8 . The…”

Section: Introductionmentioning

confidence: 99%

Untitled

Chungloo¹,

Limmeechokchai²

2009

ScienceAsia

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ABSTRACT:A solar chimney is a hot air channel attached to the roof. It enhances natural ventilation for buildings by employing the temperature difference of air at the inlet and the outlet of the channel. Experiments were carried out in an open-ended air gap, situated between the corrugated roof tile and the gypsum board, with the tilt angle of 45°of the testing building. The results showed a reduction of temperature differences between the inlet and outlet of the solar chimney for all of the daytime, implying a decrease of volume flow rate of air in the system. The hot-surface, inlet air, and outlet air temperatures were observed to increase during 8:00-12:00 and they decreased rapidly during 13:00-17:00. We obtained an empirical equation relating the Nusselt number, Rayleigh number, and the dimensions and angles of the roof. Because the equation is derived from the field experiment under the hot and humid climate, it could be used for the determination of the mean convection heat transfer coefficient of a roof solar chimney with a similar geometry.

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A laboratory experiment on natural ventilation through a roof cavity for reduction of solar heat gain

Cited by 49 publications

References 19 publications

Experimental Study of Thermal Buoyancy in the Cavity of Ventilated Roofs

Experimental Study of Thermal Buoyancy in the Cavity of Ventilated Roofs

Enhancement of stack ventilation in hot and humid climate using a combination of roof solar collector and vertical stack

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