Effects of wall proximity on the airflow in a vertical solar chimney for natural ventilation of dwellings

2020 ◽  
Vol 44 (3) ◽  
pp. 225-250
Author(s):  
Y Quoc Nguyen ◽  
John Craig Wells
Keyword(s):  
Heat Source ◽  
Natural Ventilation ◽  
Vertical Wall ◽  
Air Gap ◽  
Horizontal Plate ◽  
Solar Chimney ◽  
Horizontal Wall ◽  
Induced Flow ◽  
Air Channel ◽  
Wall Proximity

This study investigates performance of a vertical solar chimney, which absorbs solar energy and induces airflow for natural ventilation and cooling of dwellings, under effects of walls neighboring to its air channel. A computational fluid dynamics model was developed to predict induced flow rate and thermal efficiency of a vertical solar chimney with four types of nearby walls: a vertical wall to which the solar chimney was attached, a horizontal plate above the outlet of the air channel, a horizontal plate, and a horizontal wall below the inlet of the air channel. Examined factors included the heat flux in the air channel, the chimney height, the air gap, the distance of the walls, and the location of the heat source in the air channel. The results showed that effects of the wall proximity were modulated by the location of the heat source and the ratio G/ H between the air gap and the chimney height. Particularly, performance of the chimney was enhanced when the heat source was on the opposite side of the vertical wall and when G/ H was large.

Application of a Wall-Solar Chimney for Passive Cooling of Dwellings

2015 ◽  
Author(s):  
David Park ◽  
Francine Battaglia
Keyword(s):  
Energy Consumption ◽  
Flow Regime ◽  
Thermal Condition ◽  
Natural Ventilation ◽  
Energy Use ◽  
Current Model ◽  
Numerical Data ◽  
Thermal Conditions ◽  
Air Gap ◽  
Solar Chimney

Energy consumption is an important issue and has become a great concern during last the few decades, where most energy consumption is utilized for conditioning buildings. The solar chimney is a natural ventilation technique that has the potential to save energy use in buildings as well as maintain comfortable indoor quality. The objective of the current study is to examine the effects of the wall-solar chimney on airflow distribution and thermal conditions in a room. In the current work, computational fluid dynamics was used to model a solar chimney. The time-dependent conservation equations for mass, momentum and energy were solved with the k-ε turbulence equations using ANSYS Fluent. Previous literature, that utilized numerical modeling to study the solar chimney for different dimensions of chimney geometry, only considered a two-dimensional solar chimney with one-directional heat transfer. In the current study, the solar chimney was modeled three-dimensionally for a more realistic simulation of actual flow and thermal condition of the room. Experimental and numerical data from literature were used to validate the current model, and the results agreed very well. The current study showed that the flow in the solar chimney system can be either laminar or turbulent depending on the parameters of the system, and that the effect of the chimney inlet is more significant than that of the air gap on the flow regime. This study also developed a new characteristic Rayleigh number Ra* relating the chimney inlet and the air gap, which showed good consistency with the prediction of the flow regime. The investigations on Ra* and the flow regime indicated that the flow becomes turbulent for Ra* ∼ 0.8 × 108. Lastly, the potential improvements of the designs were discussed by observing the flow and thermal condition of the room.

scholarly journals EXPERIMENTAL STUDY OF SOLAR CHIMNEY PERFORMANCE FOR PASSIVE HEATING

2018 ◽  
Vol 18 (3) ◽  
pp. 375-388
Author(s):  
Majid H Majeed ◽  
Ibrahim S Resen
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Vertical Wall ◽  
Air Gap ◽  
Passive Heating ◽  
Front Side ◽  
Solar Chimney ◽  
Constant Height ◽  
Gap Width ◽  
Indoor And Outdoor

An experimental investigation on solar chimney used for heating under climate of Iraqis carried out. Experiments were conducted on the chimney installed on vertical wall withabsorber plate placed at the front side of the air gap. The solar chimney attached to room ofdimensions (2.5×1.29×1.07) m. The chimney is studied to measure the effect of the air gapwidth with constant height of (1.07 m). Three widths are tested, namely, 0.2 m, 0.3 m and0.4 m. The experimental results showed that the solar chimney can achieve about (13 °C)difference in temperature between indoor and outdoor as well as it gives acceptabledifference in partial cloudy days. The results also indicated that the best performance ofsolar chimney is with 0.3m air gap width.

scholarly journals Solar Chimney Applications in Buildings

Encyclopedia ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 409-422
Author(s):  
Haihua Zhang ◽  
Yao Tao ◽  
Long Shi
Keyword(s):  
Natural Ventilation ◽  
Energy System ◽  
Assisted Ventilation ◽  
Building Envelope ◽  
Building Structures ◽  
Solar Chimney ◽  
Climate Conditions ◽  
And Performance ◽  
Modern Building ◽  
Ventilation Systems

A solar chimney is a renewable energy system used to enhance the natural ventilation in a building based on solar and wind energy. It is one of the most representative solar-assisted passive ventilation systems attached to the building envelope. It performs exceptionally in enhancing natural ventilation and improving thermal comfort under certain climate conditions. The ventilation enhancement of solar chimneys has been widely studied numerically and experimentally. The assessment of solar chimney systems based on buoyancy ventilation relies heavily on the natural environment, experimental environment, and performance prediction methods, bringing great difficulties to quantitative analysis and parameterization research. With the increase in volume and complexity of modern building structures, current studies of solar chimneys have not yet obtained a unified design strategy and corresponding guidance. Meanwhile, combining a solar chimney with other passive ventilation systems has attracted much attention. The solar chimney-based integrated passive-assisted ventilation systems prolong the service life of an independent system and strengthen the ventilation ability for indoor cooling and heating. However, the progress is still slow regarding expanded applications and related research of solar chimneys in large volume and multi-layer buildings, and contradictory conclusions appear due to the inherent complexity of the system.

Natural-Ventilation Flow in a 3-D Room Fitted With Solar Chimney

2012 ◽  
Author(s):  
B. P. Huynh
Keyword(s):  
Heat Flux ◽  
Flow Pattern ◽  
Natural Ventilation ◽  
Air Flow ◽  
Ventilation Rate ◽  
High Heat Flux ◽  
Solar Chimney ◽  
Solar Heat ◽  
Solar Heat Flux ◽  
Inlet Opening

Natural-ventilation flow induced in a real-sized rectangular-box room fitted with a solar chimney on its roof is investigated numerically, using a commercial CFD (Computational Fluid Dynamics) software package. The chimney in turn is in the form of a parallel channel with one plate being subjected to uniform solar heat flux. Ventilation rate and air-flow pattern through the room are considered in terms of the heat flux for two different locations of the room’s inlet opening. Chien’s turbulence model of low-Reynolds-number K-ε is used in a Reynolds-Averaged Navier-Stokes (RANS) formulation. It is found that ventilation flow rate increases quickly with solar heat flux when this flux is low, but more gradually at higher flux. At low heat flux, ventilation rate is not significantly affected by location of the inlet opening to the room. On the other hand, at high heat flux, ventilation rate varies substantially with the opening’s location. Location of the inlet opening to the room also affects strongly the air-flow pattern. In any case, ample ventilation rate is readily induced by the chimney.

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