ارزیابی مبتنی بر شبیه‌سازی یک دودکش خورشیدی نصب‌شده روی دیوار برای پشتیبانی فصلی سامانه‌های تهویه مطبوع و بهره‌وری انرژی در گلخانه‌ها: مطالعه موردی در اهواز، ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی بیوسیستم، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران

چکیده

این پژوهش عملکرد فصلی دودکش خورشیدی دیواری یکپارچه با سامانه تهویه مطبوع برای کنترل اقلیم گلخانه در اهواز را ارزیابی می‌کند. با استفاده از مدل‌های معتبر دینامیک سیالات محاسباتی، عملکرد سرمایشی، تهویه‌ای و گرمایشی سامانه در یک دوره 9 ماهه و با در نظر گرفتن تغییرات دما، تابش خورشیدی و تجهیزات حرارتی یک گلخانه سقف شیروانی دوتایی با ابعاد ۱۲×۲۰ مترمربع و ارتفاع تاج ۶ متر، تحلیل شد. نتایج نشان داد که در ماه‌های گرم سال، این سامانه دماهای داخلی را 13 تا 17 درجه سلسیوس کاهش داد، اما بازده سرمایشی (56/0در برابر 62/0)، نرخ تعویض ساعتی هوا (82/3 در برابر 01/9) و شاخص یکنواختی دما (73/0 در برابر 82/0) آن در مقایسه با سامانه متعارف فن-پد کمتر بود. با این حال، حذف توان محوری فن منجر به صرفه‌جویی قابل‌توجه انرژی شد. همچنین در ماه‌های سرد سال، دما را به میزان 24/6 درجه سلسیوس افزایش داد و شاخص یکنواختی دما را از 74/0 به 89/0 ارتقا داد، هرچند بازده گرمایشی آن 43/0 و کمتر از انتظار بود. این نتایج نشان می‌دهد که این سامانه، به ویژه در دوره‌های گرمایشی می‌تواند با صرفه‌جویی در انرژی و ارائه کنترل اقلیم مؤثر، جایگزینی پایدار برای سامانه‌های متداول باشد. بهینه‌سازی طراحی، مانند استفاده از پرده‌های حرارتی و سقف‌های موقت در ماه‌های سرد، می‌تواند عملکرد آن را بیشتر بهبود دهد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Simulation-Based Evaluation of a Wall-Mounted Solar Chimney for Seasonal HVAC Support and Energy Efficiency in Greenhouses: A Case Study in Ahvaz, Iran

نویسندگان [English]

  • Seyed Majid Sajadiye
  • Ayad Saberian
Department of Biosystems Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran
چکیده [English]

This study evaluates the seasonal performance of a wall-integrated solar chimney combined with an HVAC system for greenhouse climate control in Ahvaz. Using validated computational fluid dynamics (CFD) models, the system’s cooling, ventilation, and heating performance was analyzed over a nine-month period, considering temperature variations, solar radiation, and thermal equipment in a double-pitched roof greenhouse with dimensions of 12×20 m² and a ridge height of 6 m. Results indicated that during hot months, the system reduced indoor temperatures by 13–17°C. However, its cooling efficiency (0.56 vs. 0.62), air exchange rate (3.82 ACH vs. 9.01 ACH), and temperature uniformity index (0.73 vs. 0.82) were lower than those of the conventional fan-pad system. Nonetheless, eliminating fan shaft power resulted in significant energy savings. In cold months, the system increased indoor temperatures by 6.24°C and improved the temperature uniformity index from 0.74 to 0.89, although its heating efficiency (0.43) was lower than expected. These findings suggest that the system, particularly in heating periods, offers a sustainable alternative to conventional systems by enhancing climate control while reducing energy consumption. Design optimizations, such as incorporating thermal curtains and temporary ceiling structures during colder months, could further improve its performance.

کلیدواژه‌ها [English]

  • Computational Fluid Dynamics (CFD)
  • Energy-Efficient Greenhouse Systems
  • Greenhouse Climate Control
  • Solar Chimney for HVAC
  • Sustainable Greenhouse Operations

EXTENDED ABSTRACT

Introduction

 Greenhouses play a pivotal role in sustainable agriculture, providing controlled environments for crop production regardless of external climatic conditions. However, climate control in greenhouses, particularly in regions with extreme temperatures, often demands significant energy resources. This study investigates the performance of a solar chimney-assisted HVAC system for a greenhouse located in Ahvaz, Iran, comparing it with a conventional HVAC system. By harnessing buoyancy-driven natural ventilation, the solar chimney aims to reduce reliance on mechanical components, thereby minimizing energy consumption and operational costs. Through computational fluid dynamics (CFD) modeling, the research explores the system’s effectiveness in maintaining optimal thermal conditions across varying seasonal climates.

Materials and Methods

The study employed validated CFD models to simulate the thermal dynamics of a solar chimney-assisted HVAC system in a greenhouse. Key parameters included greenhouse thermal properties, HVAC configurations, and fluctuating solar heat loads influenced by local weather conditions. Performance metrics such as air exchange rates (ACH), temperature uniformity index (TUI), indoor and canopy temperatures, and HVAC efficiency analyzed over a 9-month period. The greenhouse was divided into cooling (May to September) and heating (November to February) phases to assess system efficiency under diverse climatic scenarios. System components, including a solar chimney, wet pad, and fans, were modeled to evaluate airflow patterns, temperature distribution, and energy efficiency.

Results and Discussion

The solar chimney-assisted system demonstrated notable energy savings by eliminating the need for mechanical fan power, albeit with some cooling limitations in extreme heat. During cooling months, the system achieved an average temperature reduction of 13–17°C, keeping canopy temperatures within acceptable limits. However, its cooling efficiency (ηc) was slightly lower (0.56) compared to the conventional system (0.62). Despite reduced ACH (3.82 vs. 9.01) and TUI (0.73 vs. 0.82), the solar chimney’s passive ventilation showed potential for further optimization. For heating, the solar chimney raised indoor temperatures by an average of 6.24°C, though its heating efficiency (ηh) was modest (0.43) due to rapid thermal equilibrium and heat loss to the cold ceiling. Proposed improvements, such as thermal curtains or temporary lower ceilings, could mitigate heat transfer and enhance system performance. Notably, the system maintained a more consistent canopy temperature (27.01°C, TUI: 0.92) compared to the conventional system’s unheated state (25.37°C, TUI: 0.75). The solar collector’s thermal efficiency was low (0.13 in summer, 0.09 in winter), reflecting its design’s prioritization of ventilation over heat capture.

Conclusion

The solar chimney-assisted HVAC system presents a sustainable solution for greenhouse climate control by significantly reducing energy consumption while maintaining conditions suitable for crop growth. However, its cooling capacity under extreme heat and heating efficiency in colder months require further improvement. Future research should focus on optimizing chimney height and wet pad airflow, integrating hybrid cooling strategies, and conducting comprehensive economic assessments to determine long-term feasibility. Given that these findings are specific to the climatic conditions of Ahvaz, further investigations across diverse climates and greenhouse configurations are necessary to assess the system’s adaptability. With continued refinement and scalability, solar chimney-assisted systems have the potential to transform energy-efficient agriculture, particularly in arid and energy-limited regions.

Author Contributions

All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.

Data Availability Statement

Not applicable

Acknowledgements

The authors would like to thank all participants of the present study.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest. 

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مهندسی بیوسیستم ایران
دوره 55، شماره 3
مهر 1403
صفحه 87-108

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  • تاریخ دریافت: 20 دی 1403
  • تاریخ بازنگری: 26 بهمن 1403
  • تاریخ پذیرش: 14 اسفند 1403

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