Journal of Iranian Architecture & Urbanism(JIAU)

Modifying the air flow pattern in cattle barns of Salmas city through architectural intervention to improve the ventilation

Omid Rahaei; Mehri Barehyun

Volume 14, Issue 1 , August 2023, , Pages 311-326

https://doi.org/10.30475/isau.2023.368528.2003

Abstract

Extended AbstractBackground and Objectives: Observations show that most of the cattle barns built in Iran are in the form of sheds, and during their design phase, limited consideration ... Read More Extended AbstractBackground and Objectives: Observations show that most of the cattle barns built in Iran are in the form of sheds, and during their design phase, limited consideration is given to ventilation conditions, despite the significant need for it, as well as the air circulation patterns within the barns. This oversight leads to numerous issues in the field, with the well-being of the animals subsequently affected. The main goal of the article is to improve the ventilation of in cattle barns, through architecture, in such a way that the optimal and uniform air flow is established throughout the environment, at the level where animals live. According to the nature of the subject, the current research is an interdisciplinary research and a hybrid research method is applied using experimental research strategies, simulation and case study. In the first stage, after identifying the statistical population (cattle barns in the cold region), their current situation was investigated empirically, and after scrutinizing the problem and finding the research variables, the initial plan (case sample) was proposed and modeled. The desired model was first meshed with Gambit, subsequently undergoing simulation via the FLUENT software employing the CFD methodology. Adjustments were introduced to its architectural design, followed by the analysis and formulation of conclusions. The results show that, by making minimal architectural changes to the barn and the openings, it is feasible to enhance the airflow pattern within it. This can effectively establish internal air circulation, diminish temperature disparities among various barn sections, minimize temperature fluctuations, and lower energy consumption. Methods: Considering its interdisciplinary nature, the research employs a hybrid approach that combines experimental research, simulation, and case study strategies. The research encompasses all cattle barns in cold climates as the statistical population. The chosen case study focuses on a cattle barn designed for approximately 250 cows in the city of Salmas. The research findings indicate that enhancing the architectural layout and positioning of openings, along with their primary composition, can lead to improved ventilation in cattle barns and a more uniform airflow within them. The research utilizes numerical simulation, specifically in the case of a Salmas city cattle barn, validated previously through Olsen’s experimental methods (Rahaei, 2014, 2013). The validation of this method is well-established and is based on Nagano’s (1990) validated technique, utilizing a zero-equation method and model. The numerical calculations are conducted using the computational fluid dynamics method, employing the Gambit preprocessor for meshing and Fluent software for network analysis.Findings: Considering the research goal of enhancing airflow and subsequently ventilation in cattle barns in climates similar to Salmas city (the cold climate), various scenarios of a common case study were examined in a two-dimensional manner. Initially, longitudinal sections were analyzed, followed by transverse sections of the cattle barn. In all scenarios, the energy equation was activated. The optimal condition involves a smooth and favorable inward airflow through side windows. Afterward, this airflow undergoes conditioning as it passes through the radiators installed in the windows and, if necessary, proper dehumidification is achieved with the assistance of mist sprinklers. Minimal energy is drawn from the lower part of the area occupied by the animals and is expelled through the roof opening.Conclusion: Based on the above-mentioned resources, the following are suggested in the case of longitudinal and transverse ventilation of cold climate cattle farms:1. Unpredicted entry of outside air into the interior of cattle barns should be strictly avoided.2. If the entire space of the barn is used, the use of a longitudinal one-way ventilation mechanism is required, while all the openings are closed. It is recommended to incorporate a temperature control source, such as a radiator, positioned at a height of 3 meters above the main floor level, equipped with both hot and cold water supply, at one side of the barn. Simultaneously, a suction device (jet fan) should be installed at floor level on the opposite side, expelling air outward. In this setup, fresh outdoor air, having passed through the radiator, becomes conducive and enters the enclosure. Following even distribution of this air to achieve a desirable temperature within the environment, it exits through the suction system located on the opposite side. Additionally, a pressure regulating valve should be installed at the lower level of the side housing the radiator, which can be closed during colder seasons.3. If it is possible to change the interior space of the cattle barn, lateral ventilation is suggested from both sides.4. In general, transverse ventilation with a roof valve is more efficient than ventilation along the cattle barn.

Improving the climate performance of solar chimneys for Ahvaz houses in south equator-facing rooms

Omid Rahaei; Zeynab Poorsayahi

Volume 13, Issue 1 , May 2022, , Pages 245-257

https://doi.org/10.30475/isau.2022.221907.1365

Abstract

Extended AbstractBackground and Objectives: Today, the use of solar energy as a cheap and renewable source in the construction industry has become one of the major concerns worldwide. ... Read More Extended AbstractBackground and Objectives: Today, the use of solar energy as a cheap and renewable source in the construction industry has become one of the major concerns worldwide. One way to harness solar power is to use a solar chimney in the building. The solar chimney acts as a passive natural ventilation system or as a thermal insulator based on pressure displacement caused by air pressure fluctuations inside the chimney shaft. This chimney usually consists of glass, duct, and absorber surface. The air in the chimney is heated by solar energy and moves upwards due to the chimney effect, which can increase the natural ventilation in the adjacent spaces. In hot and semi-humid climate buildings, windows are usually closed to prevent direct sunlight. Therefore, solar chimneys can establish airflow and supply fresh air indoors. The ventilation process in buildings of Ahvaz city, due to particular climatic conditions (hot and semi-humid), is essential. Also, air conditioning is costly, consuming a great amount of energy. Therefore, this study aims to find appropriate criteria for the effective design and implementation of solar chimneys in houses in Ahvaz to establish an effective flow inside the air duct in seasons requiring thermal comfort conditions and to create effective ventilation inside the interior spaces through stack effect. This study aims to find a suitable model for designing solar chimneys for the southern (equator-facing) rooms of houses in Ahvaz city (hot and semi-humid climate) to improve the thermal comfort of residents by using solar energy effectively and reducing energy consumption significantly.Methods: This research combines different methods due to its interdisciplinary nature. Research variables and models were identified in the first stage using an experimental strategy. The physical structure of the room and the solar chimney were studied as independent variables and the room interior temperature as a dependent variable in this study. A digital thermometer was used for experimental thermometry tests in the case sample. The statistical population selected in this study includes southern rooms in apartments in Ahvaz. The statistical population is a small room as a random case sample. In the next step, solar chimneys were modeled in Ecotect software, and a simulation method was used to analyze the data and intervene in the architecture. The simulations were performed using Energy Plus software version 8.7.0 and the existing weather data (regarding the literature). Also, the simulations were calculated linearly and thermodynamically by TARP thermal model method prepared by Walton (1983) in the software. The Fangar comfort model, PMV index, and PPD were used in the next step of data analysis. Finally, the experimental data were compared to the simulated data to investigate research validity and reliability. Thus, the research method is a combination of experimental strategies, simulation, and a case study. Bibliographic studies, field observations, field measurements, and simulations were used as research tools.Findings: In this study, four different models of solar chimneys on a specific day were studied to investigate the effect of geometry on the model discharge. Also, the thermal comfort (of the first model) was studied on a specific day of the year. (The reason for choosing this model is to investigate the chimney effect on the whole space). The simulation data of the first model with dimensions of 1 × 1.16 × 11.60 showed that the thermal comfort level in this type of solar chimney is close to the allowable limit in March, April, May, June, October, and, November, December. According to the diagrams, using this type of chimney is unsuitable in July, August, and September, so this model is not approved. On May 1st, the effect of the number of floors on the thermal performance of the first model was investigated. The results showed that the solar chimney discharge does not always lead to acceptable thermal comfort conditions. Also, four specific geometries were compared regarding the effect of geometry on the solar chimney discharge. According to findings, the solar chimney height was more effective in determining the maximum and average solar chimney flow than its width. According to the results, the third model has a more powerful airflow but drops to zero at certain hours and has no night ventilation. So, having a chimney with a maximum flow is not necessarily appropriate. The best model, according to the comparative method, is the second model with dimensions (2 × 1.16 × 11.60), and then the third model with dimensions (1 × 1.16 × 23.20), with strong airflow powers.Conclusion: By examining the airflow and thermal comfort conditions in solar chimneys, it was determined that the airflow could create suitable comfort conditions in the building annually. Therefore, the solar chimney with dimensions of 2 × 1.16 × 11.60 (model 2) is suitable for equator-facing rooms with dimensions of 3.5 × 5.9 meters in Ahvaz and can provide comfort levels in the mentioned months. According to the results, this system is needed all year round. When there are no comfort conditions, it is recommended to benefit from mechanical systems, ventilation and air conditioning, green space, and natural ventilation systems for comfort conditions.

Improving the Quality of Natural Ventilation in Classrooms of Mazandaran Province Based on the Position of the Openings Using CFD Method

Omid Rahaei; Hamid Reza Azemati

Volume 11, Issue 1 , August 2020, , Pages 57-71

https://doi.org/10.30475/isau.2020.161257.1140

Abstract

Extended Abstract Introduction: Providing clean and fresh air for students in the classroom is of paramount importance, especially in hot seasons. Based on research findings and evidences, ... Read More Extended Abstract Introduction: Providing clean and fresh air for students in the classroom is of paramount importance, especially in hot seasons. Based on research findings and evidences, mechanical air conditioning systems are not only expensive, but also consume a lot of energy and produce noise. In sultry conditions of Mazandaran province, this issue is more accentuated since the schools are cooled by evaporative air coolers, while it is possible to use the natural ventilation in a better share of the year, and the schools are closed in warm seasons. Hence, the purpose of this paper is to offer a practical solution that can be architecturally applied to the classrooms to improve the indoor airflow by inducing outdoor ventilation (natural ventilation), and provide a desirable and controllable indoor airflow according to the ASHRAE standard. In most Iranian schools, evaporative air coolers are used in hot seasons to reduce the high costs of air conditioning systems. Observations suggest that evaporative air coolers are also used in hot and humid climate near the Caspian Sea, resulting discomfort, particularly with high levels of humidity. In such cases, the evaporative air coolers are turned off and the windows are opened. Mostly, the induced indoor airflow is not effective, or a high flow of air enters the classroom in these situations. Problem statement: Achieving comfort at schools in sultry conditions in hot and humid weather of northern Iran is challenging, and thus it is necessary to establish an effective air conditioning system in the classrooms. Moreover, natural ventilation is the best solution in these conditions according to the climatic and economic reasons. Natural ventilation should consistently induce airflow in all parts of the classroom at a reasonable velocity. Hence, this research investigates the criteria for designing classrooms in the climate of Amol, considering the position and the general configuration of the openings in the classrooms, and the direction of the prevailing wind to induce a controlled level of natural ventilation in all parts of the classroom. The main purpose of this article is to address these issues. Research methodology: According to the literature, the present study is interdisciplinary in nature, and uses a combination of methods. The position of the openings and the composition of classrooms were examined as the independent variables, while the status of the indoor airflow was considered as the dependent variable in this research. The airflow velocity and direction were measured by precise digital devices during the test periods. The statistical population selected in this study includes all schools of Amol while a random case study was selected for further experimental tests. In the next step, a simulation method was used to analyze the data for evaluating the architectural interventions. Simulations were performed by computational fluid dynamics method: The Gambit pre-processor was used for geometric modeling and grid generation, and Fluent Software was used to analyze the grid. In this study, the standard model was used to simulate airflow. Thus, this research uses a combination of methodologies including experimentation, simulations and case study. Results: After examining different tests, an optimal situation was selected according to the following criteria: Increased velocity of the indoor airflow in classrooms which (1) is not disturbing and, (2) provides a consistent airflow for all of the students at all spots of the classroom. Eliminated vortices in indoor airflow Modified airflow direction Properly directed outdoor airflow into the indoor space and an induced desirable airflow According to the interventions made in this study, it was determined that both windows must act as air inlets to establish effective airflow in the classroom. The inlet air pressure to both windows must be approximately the same, and the outlet air flow from both windows must be approximately equal as well. This happens when the building facade and the exterior windows have a stepped configuration, and consequently the outdoor airflow can enter both windows equally. If there is no proper outlet considered for the air entering the classroom, the indoor air flow will be very turbulent. Therefore, devising an appropriate outlet based on the inlet airflow rate can balance the indoor air flow. According to the simulations, an outlet for the indoor air flow should be made within the wall facing the wind. In other words, if the wind is blowing from the west to the east, the indoor air outlet must be projected on the west wall of the classroom. In this case, the exit door should also be devised in the southwest corner of the classroom. Some air outlets can be created (in the western wall) that act as a fan, a suction pipe, or an air outlet opening in the wall facing the wind, so that the air exits through the pipes in the wall. The suction rate of the western wall can regulate the internal air flow. Moreover, if the wind velocity is too high in the outdoor, the suction devices are turned off or slowed-down, and if the wind velocity is low, the suction devices can discharge more air. In this case, the shape of the indoor air flow is optimized and adjusted.

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Author = Rahaei, Omid

Modifying the air flow pattern in cattle barns of Salmas city through architectural intervention to improve the ventilation

Abstract

Improving the climate performance of solar chimneys for Ahvaz houses in south equator-facing rooms

Abstract

Improving the Quality of Natural Ventilation in Classrooms of Mazandaran Province Based on the Position of the Openings Using CFD Method

Abstract