Influence of inlet height and collector volume on thermal and flow characteristics of solar updraft towers

초록

A solar updraft tower (SUT) is a renewable energy system whose performance depends strongly on its structural configuration. Structural modifications intended to enhance performance inevitably alter the internal volume of the system. However, the role of internal volume in governing thermal storage and airflow behavior remains unclear, making it difficult to distinguish whether performance changes arise from volumetric effects or geometric design parameters. This study investigates the effect of inlet height and collector volume by introducing volume-coupled inlet (VCI) and volume-decoupled inlet (VDI) configuration, enabling isolation of volume-related effects. A numerical thermofluid analysis was conducted to evaluate flow behavior and energy conversion characteristics. Both VCI and VDI models improved the SUT performance by 15.91% and 15.49%, respectively, compared with the control case. Although the VDI model, which maintains a constant internal volume, increased internal temperature and thermal capacity, it did not enhance overall performance due to increased flow resistance that suppressed air flow acceleration. In contrast, the VCI model, which allows volume variation, achieved higher efficiency by more effectively converting thermal energy into kinetic energy and sustaining a higher mass flow rate through the chimney. These findings highlight that preserving favorable flow structures is more critical than increasing thermal storage for improving SUT performance. The findings provide design insights applicable to solar thermal collector systems with similar operating principles.

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