Conference Proceedings - 2021

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http://repository.vlu.edu.vn:443/handle/123456789/1422

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Browsing Conference Proceedings - 2021 by Subject ""Atmospheric radiation"
  • Publication
    Effects of a fin on the wall of the air channel on the performance of a trombe wall for natural heating
    ( 2021)
    V. T. Nguyen
    ;
    Y. Q. Nguyen
    A Trombe wall can be installed in buildings to reduce electricity consumption. Trombe walls are designed to absorb and store solar radiation. By thermal effects, cool air enters the air channel from the inlet and is heated during the channel’s passage. The warm air rises and is fed back into the building to achieve energy efficiency. In this study, an investigation on the induced flow rate and temperature rise was carried out with a fin’s presence by a numerical method based on Computational Fluid Dynamics (CFD) technique. The location and length of the fin were changed to improve the system performance. This work demonstrated that an increase of 16° C in temperature at the outlet can be achieved with a distance of 0.1 m between the fin and the inlet. The fin added inside the Trombe wall channel is an approach to achieve thermal comfort in sustainable building design
  • Publication
    Effects of suction flow on the performance of a solar chimney
    ( 2021)
    Y. Q. Nguyen
    ;
    T. N. Huynh
    Solar chimney has been applied on various aspects of building physics and green design. It makes natural ventilation based on stack effect from absorbing solar radiation. A Computational Fluid Dynamics (CFD) method has been widely utilized to model the heat transfer and air flow inside the chimney. The appearance of reverse flow is one of the elements affecting induced results from CFD models. In this study, we examined influences of the suction flow to suppress the reverse flow at the outlet of the air channel. The suction height, suction width and the velocity of the exhaust fan were investigated. The induced flow rate and temperature rise of the chimney were compared to the base case, which has no suction flow. It is observed that the ratio of Qsc and Qbase, which are the induced flow rate at the outlet of the chimney which has exhaust fan and induced flow rate of the base case, respectively, increases with the width, w, and the height above the inlet, h, of the suction port then gradually approaches a constant of about 1.25 when w and h are higher than 0.02 m and 0.15 m correspondingly. Additionally, one advantage of the suggested solution is to lower the noise from the fan to the room
  • Publication
    Effects of the forced air temperature on the induced flow rate through a combined natural–forced flow in a solar chimney
    ( 2021)
    Y. Q. Nguyen
    ;
    Minh-Thu T. Huynh
    ;
    Tung V. Nguyen
    With a good design, solar chimney is able to provide sufficient natural ventilation for buildings. In practice, natural ventilation performance depends on many factors, such as solar radiation, which is intermittent. Therefore, in this study, a proposed combined natural–forced flow solar chimney is investigated. Induced ventilation rate is estimated under the effects of the temperature of the forced flow and compared to that of the base case which has no forced flow. The results show that, with a forced flow velocity of 1.0 m/s and a heat flux of 500 W/m2, the induced mass flow rate increases when the forced flow temperature increases from 20 to 35oC. Compared with the base case, the combined natural–forced flow offers more flow rate as the gap G is above 0.05 m at the height, H, of solar chimney H of 0.45 m; 0.1 m at H=0.95 m; 0.15 m at H=1.45 m, and 0.2 m at H=2.0 m. It is expected that with a proper design, improvement of ventilation performance of a solar chimney can be achieved by this combined natural–forced flow
  • Publication
    Numerical investigation on an indirect type of natural solar collector for drying
    ( 2021)
    Tue Nguyen Duy
    Drying which is the important process in the preservation of food picks up the moisture in the wet product and keep it at the lower moisture content. However, this process needs the energy to heat air from ambient temperature to nearly 80° -100°C to extract moisture from the wet product. With the advantage of having the existing high solar radiation intensity in Viet Nam, solar energy can be harnessed to heat air in this process. In this paper, the author designed the triangle finned solar collector of an indirect type natural solar drying and investigated its thermal performance at 13 pm, through 12 months, the face of the south, location in Can Tho province by using Computational Fluid Dynamic (CFD). The result shows that the outlet temperature of the solar collector ranges from 75.8°C to 88.46°C with the natural air flowrate from 10.34 g/s to 11.94 g/s, so it is eligible for agricultural drying. The natural air flowrate strongly depends on the solar radiation which strikes the solar collector. The higher solar radiation, the higher air flow rate that can be acquired.