Hot air recirculation around air-cooled heat exchangers in plants

2022 Fiscal Year Final Research Report

• Project Area: Micro-meteorology control: Integrated technology of harmonic prediction and active monitoring of micro-meteorology for future autonomous society
• Project/Area Number: 20H05754
• Research Category: Grant-in-Aid for Transformative Research Areas (B)
• Allocation Type: Single-year Grants
• Review Section: Transformative Research Areas, Section (II)
• Research Institution: Nagoya University
• Principal Investigator: Watanabe Tomoaki 名古屋大学, 工学研究科, 准教授 (70772292)
• Co-Investigator(Kenkyū-buntansha): 長田 孝二 名古屋大学, 工学研究科, 教授 (50274501)
• Project Period (FY): 2020-10-02 – 2023-03-31
• Keywords: 微気象 / 流体工学 / Hot Air Recirculation / プラント / 数値シミュレーション

Outline of Final Research Achievements

Numerical simulations were performed for jets in a crossflow, which resemble heat dispersion observed for air-cooled heat exchangers used at plants. High-temperature fluid tends to stay near the ground because of the interaction of the multiple jets and the swirl motion of the jets. The process by which long-elongated turbulent structures with high temperature are generated was investigated by numerical simulations of turbulent flows. A flow similar to the hot-air recirculation at plants was successfully reproduced in wind-tunnel experiments of a model of air-cooled heat exchangers. Observational experiments were also conducted to obtain data on heat dispersion in a microclimate environment. These phenomena were shown to be well predicted by microclimate simulations.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

大型プラント内の列をなした空冷式熱交換器において、高温排熱気塊が風下側の熱交換器や各種装置に吸い込まれる事により装置の性能低下を引き起こすHot Air Recirculation（HAR）と呼ばれる現象が問題になっている。本成果によりプラントにおいてHARを引き起こす可能性がある現象が明らかとなった。また、HAR類似現象を微気象シミュレーションにより再現できることが確認された。微気象シミュレーションから得られる情報を基にHAR発生を事前予測しプラント運用を最適化することにより、HAR現象に起因するプラント運用効率の低下を防ぐことができると期待される。