Enhancement of Gravity Ventilation in Buildings

2017 ◽  
Author(s):  
Magdalena Nakielska ◽  
Krzysztof Pawłowski
Keyword(s):  
Natural Ventilation ◽  
Air Flow ◽  
Electrical Energy ◽  
Climatic Conditions ◽  
Demand Systems ◽  
Solar Chimney ◽  
Correct Operation ◽  
Research Results ◽  
Heat Demand ◽  
Flow Through

Nowadays, people are looking for solutions related to ventilation, cooling or heat demand systems, which would be energy efficient and, at the same time, would not cause the degradation of the surrounding environment. As far as ventilation is concerned, an good solution is a natural ventilation, which improves thermal comfort rooms without increasing the consumption of electrical energy in the building. In order to improve the mode of action of the natural ventilation in the building, one can mount various elements supporting the air flow. One of them is a solar chimney. In order to check the correct operation of a gravity ventilation installation in Poland’s climatic conditions, the measurements was carried out on a test stand on the 3.1 building of UTP University of Science and Technology in Bydgoszcz. The received results show the intensification of the air flow through the room the value between 50% and 150%, depending on a measuring hour (Chen et al. 2003). These research results were compared with the research results received before the installation of the solar chimney on the ducts of the gravity ventilation.

Effect of Inlet Location on Ventilation Flow Through a Room Fitted With Solar Chimney

2018 ◽  
Author(s):  
Kashif Nazir ◽  
B. P. Huynh
Keyword(s):  
Solar Radiation ◽  
Flow Pattern ◽  
Natural Ventilation ◽  
Air Flow ◽  
Ventilation Rate ◽  
Navier Stokes ◽  
Computational Domain ◽  
Solar Chimney ◽  
Flow Through ◽  
Inlet Opening

Solar chimney (thermal chimney) is a device which absorbs solar radiation to heat the air. The heated air, becoming buoyant, rises through the chimney’s passage and induces further air currents. When fitted to a building, solar chimney can thus induce fresh outside air to flow through the building for ventilation. Because only natural means (solar radiation here) are involved to cause the air flow, solar chimney is considered a natural-ventilation device. This work investigates computationally natural ventilation induced by a roof-mounted solar chimney through a real-sized 3-dimensional room, using a commercial CFD (Computational Fluid Dynamics) software package which employs the Finite Volume Method. Chien’s turbulence model of low-Reynolds-number K-ε is used in a Reynolds-Averaged Navier-Stokes (RANS) formulation. Computational domain that includes regions outside the room’s inlet opening and chimney’s exit allows for employing realistic boundary conditions for the computational model. Ventilation rate and air-flow pattern through the room are considered in terms of the location of the room’s inlet opening. It is found that while ventilation flow-rate through the room is higher with the room-inlet opening being located high on the wall opposite to the chimney’s entrance, a room-inlet opening being located near the ground results in better flow pattern with more flow through the living area in the lower part of the room.

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.

scholarly journals Analysis of the influence of selected factors on natural greenhouse ventilation

2018 ◽  
Vol 49 ◽  
pp. 00036
Author(s):  
Sławomir Grabarczyk
Keyword(s):  
Wind Speed ◽  
Natural Ventilation ◽  
Air Flow ◽  
Leeward Side ◽  
Air Exchange Rate ◽  
Solar Radiation Intensity ◽  
Thermal Screen ◽  
Flow Through ◽  
American Society ◽  
Air Exchange

In greenhouses, in order to maintain proper indoor air temperature, during the period of high values of solar radiation intensity, shading treatments using thermal screens and ventilation are applied. The research was carried out in a mono-span greenhouse in order to determine the effectiveness of natural ventilation. The object of analysis is a greenhouse with a thermal screen installed inside. The tests were carried out during the summer days. The effect of the research was to determine the ventilation air flow through the vents of the greenhouse on the basis of measurements and calculation analyzes. The dependence of the air flow on the windward and leeward side was determined from the wind speed and the temperature difference between the indoor and outdoor air. On the basis of calculations made from observation during shading of the cultivated area and with open ventilators, the coefficients of air exchange per unit floor area of the greenhouse were determined. It was established that at a wind speed exceeding 0.8 m/s, the air exchange rate in the tested greenhouse exceeds the value recommended by the American Society of Agricultural Engineers of 0.04 m3/(s.m2).

Research of Window's Discharge Coefficient in the Natural Ventilation Room

2014 ◽  
Vol 525 ◽  
pp. 420-426
Author(s):  
Qi Hai Liao ◽  
Yan Ling Guan ◽  
Qiao Ning Wang
Keyword(s):  
Pressure Difference ◽  
Natural Ventilation ◽  
Discharge Coefficient ◽  
Test Bench ◽  
Air Flow ◽  
Experimental Conditions ◽  
Flow Through

Discharge coefficient of window is one of the important factors in natural ventilated calculation, while there are many factors may impact the windows discharge coefficient. This article adopts the method of experiment, simulate the natural ventilation of room on the test bench , by measuring the pressure difference of both sides of window and the air flow through the window under different experimental conditions, analyze how the opening rate of window and the air flow impact the values of discharge coefficient of window, and giving the value of discharge coefficient of window under the experiment condition, hoping to provide help to the use of natural ventilation of building effectively.

Simulation of Ventilation Flow at Different Conditions Through a Two-Dimensional Room Incorporated With Phase Change Materials

2020 ◽  
Author(s):  
Angel Reyes-Cubas ◽  
Peter Abdo
Keyword(s):  
Energy Consumption ◽  
Phase Change ◽  
Natural Ventilation ◽  
Phase Change Materials ◽  
Liquid Fraction ◽  
Air Flow ◽  
Building Energy Efficiency ◽  
Two Dimensional ◽  
Latent Heat Storage ◽  
Flow Through

Abstract Climate change and global warming have raised many concerns, highlighting the necessity to reduce energy consumption associated with the building sector. HVAC systems account to almost 40% of the building’s energy consumption. Natural ventilation is the process of supplying and removing air through an indoor space by natural means. Windcatchers have been used over centuries for providing natural ventilation using wind power. Moreover, it is an effective passive method to provide healthy and comfortable indoor environment by decreasing moisture content in the air and reducing pollutants concentration significantly. Materials that change phase at certain temperature are frequently referred to as Phase Change Materials (PCMs). Phase Change Materials, also known as Thermal Energy Storage (TES), are substances with high latent heat storage capacity which absorb or release the heat from or to the surrounding environment. PCMs could be used in passive cooling systems and they are directly related to building energy efficiency. This study investigates air flow through a windcatcher into a two-dimensional room incorporated with phase change materials (PCMs). The temperature change in the room implementing PCM is analyzed to monitor the PCMs’ performance. To achieve this, Computational Fluid Dynamics (CFD) tool is used to simulate the air flow through a two-dimensional standard room (3 m × 5 m) fitted with a windcatcher at its roof. Ansys Fluent is utilized to simulate and display the contours of temperature, liquid fraction, and velocity of both PCM and air. The energy model as well as the solidification and melting model are employed, and the K-Epsilon turbulence model is implemented. PCM is placed at the right and left walls of the room, as well as at its bottom. The inlet velocity ranges between 1 m/s and 7 m/s, simulating the average wind speeds in Sydney-Australia during summer [1]. Different inlet temperatures are used, specifically at 302 K and 310 K. The effect of the phase change material presence on the air flow pattern is also investigated.

A LES Study of Ventilation Flow Through a 3-D Room Fitted With Solar Chimney

2020 ◽  
Author(s):  
B. Phuoc Huynh
Keyword(s):  
Solar Radiation ◽  
Natural Ventilation ◽  
Boussinesq Approximation ◽  
Scale Model ◽  
Navier Stokes ◽  
Solar Chimney ◽  
3 Dimensional ◽  
Fluid Properties ◽  
Flow Through ◽  
Volume Method

Abstract Solar chimney (thermal chimney) is a device which absorbs solar radiation to heat the air. The heated air, becoming buoyant, rises through the chimney’s passage and induces further air currents. When fitted to a building, solar chimney can thus induce fresh outside air to flow through the building for ventilation. Because only natural means (solar radiation here) are involved to cause the air flow, solar chimney is considered a natural-ventilation device. This work investigates computationally natural ventilation induced by a roof-mounted solar chimney through a real-sized 3-dimensional room, using a commercial CFD (Computational Fluid Dynamics) software package which employs the Finite Volume Method. A LES (Large-Eddy Simulations) formulation with Smagorinsky SGS (Sub-Grid Scale) model is used. All fluid properties are assumed to be constant and corresponding to those of air at 300K (27°C, constant ambient temperature) and standard pressure at sea level (101.3kPa); but Boussinesq approximation (wherein temperature change affects only the fluid density pertaining to buoyancy force) is also assumed. Comparison is made with computational results obtained from a RANS (Reynolds-Averaged Navier-Stokes) formulation. Agreement between LES and RANS results indicate the trustworthiness of CFD methods used.

Effect of Wind Speed on Ventilation Flow Through a Two Dimensional Room Fitted With a Windcatcher

2018 ◽  
Author(s):  
Rahil Taghipour ◽  
Peter Abdo ◽  
B. P. Huynh
Keyword(s):  
Indoor Environment ◽  
Natural Ventilation ◽  
Air Flow ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Indoor Space ◽  
Wind Speeds ◽  
Flow Through ◽  
Convergent Inlet ◽  
Natural Means

Natural ventilation is the process of supplying and removing air through an indoor space by natural means. Windcatcher has been used over centuries for providing natural ventilation using wind power, it is an effective passive method to provide healthy and comfortable indoor environment by decreasing moisture content in the air and reducing pollutants concentration. The windcatcher’s function is based on the wind and on the stack effect resulting from temperature differences. Generally, it is difficult for wind to change its direction, and enter a room through usual openings, the windcatcher is designed to overcome such problems since they have vertical columns aimed at helping wind to channel down to the inside of a building. The efficiency of a windcatcher is maximized by applying special forms of opening and exit. The openings depend on the windcatcher’s location and on its cross sectional area and shape such as square, rectangular, hexagonal or circular. In this study the effect of different wind speeds on the total air flow captured by different inlet designs is investigated. To achieve this, CFD (computational fluid dynamics) tool is used to simulate the air flow in a two dimensional room fitted with a windcatcher applying wind speeds from 1 m/s up to 14 m/s and based on different inlet designs such as a uniform inlet, a divergent inlet and a bulging-convergent inlet.

CFD investigation of temperature distribution, air flow pattern and thermal comfort in natural ventilation of building using solar chimney

2020 ◽  
Vol 17 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Maher Dhahri ◽  
Hana Aouinet
Keyword(s):  
Heat Flux ◽  
Temperature Distribution ◽  
Thermal Comfort ◽  
Natural Ventilation ◽  
Air Flow ◽  
Solar Chimney ◽  
Air Velocity ◽  
Content Type ◽  
Solar Heat ◽  
Solar Heat Flux

Purpose The purpose of this study is to investigate air flow, temperature distribution and thermal confort in natural ventilation induced by solar chimney for different operating. Design/methodology/approach Numerical simulation is performed using a commercial computational fluid dynamics (CFD) package ANSYS CFX software to understand the effects of air temperature, air velocity and solar heat flux on the performance of the solar chimney and thermal comfort. The comfort level was evaluated using the air diffusion performance index (ADPI) according to ASHRAE (55-210). The flow was investigated at inclination angles 45° solar heat flux 550-750 W/m2 and in a solar chimney of 1.4 m length, 0.6 m width and 0.20 m air gab. Findings The numerical results from the present simulation were first validated with experimental data, which was used for the thermal comfort indexes calculation. The obtained results of the analysis showed that the used numerical technique could accurately predict air flow and temperature distribution in natural ventilated building using solar chimney; the air temperature, air velocity and solar heat flux have a significant impact on thermal comfort; the temperature of 19°C with velocity of 0.15 m.s−1 gives the best effective draft temperature (EDT) satisfy ASHRAE (55-210) criteria that V = 0.35 m.s−1 and EDT range between −1.7 and 1.1. Originality/value In the present paper, air flow, temperature distribution and thermal comfort inside a room equipped with inclined solar chimney were numerically investigated and analyzed. The commercial CFD package (CFX 15) is used. Calculations are carried out in an empty room without any human or mechanical activity and the numerical results are compared with measurement points.

scholarly journals Análisis teórico de una chimenea solar con tres canales de flujo de aire

2019 ◽  
pp. 13-19
Author(s):  
Angel Tlatelpa-Becerro ◽  
Ramiro Rico-Martínez ◽  
Gustavo Urquiza-Beltrán ◽  
Elva Lilia Reynoso-Jardón
Keyword(s):  
Natural Ventilation ◽  
Single Channel ◽  
Residential Buildings ◽  
Air Flow ◽  
Tropical Region ◽  
Solar Chimney ◽  
Climatic Zones ◽  
The Cost ◽  
Energy Balances ◽  
Ventilation Systems

A solar chimney configuration consisting of three air flow channels divided by two metallic plate, placed in the center of the chimney between two acrylic covers, leading to symmetric air flow, is proposed as an alternative for the design of natural ventilation systems for buildings in tropical and subtropical climatic zones The solar chimney dimensions are 2.0 m height, 1.0 m width, and gap between channels of 0.30 m. These dimensions are appropriate for the design of ventilation systems for residential buildings in central México. A Numerical simulation using the global mass and energy balances in steady state was utilized to evaluate the efficacy of the proposed configuration. The temperature profiles, calculated for a typical hot day in a tropical region, reveal that the configuration is more efficient than the single channel chimney, achieving thermal efficiency values near 75%. This solar chimney configuration can be used with better results than the traditional design as an alternative for natural ventilation systems in residential buildings without a significant increase in the cost of the residence investment.

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