A04　Phenomenon Modeling Group | Planned Research | Micro-meteorology control：Integrated technology of harmonic prediction and active monitoring of micro-meteorology for future autonomous society | Grant-in-Aid for Transformative Research on Area (B)

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A04 Phenomenon Modeling Group

Research Task: A04: Modelling the cause of abnormal hot exhaust mass in large factories

Principal Investigator: Tomoaki Watanabe
Associate Professor, Graduate School of Engineering, Nagoya University
https://www.fdl.mae.nagoya-u.ac.jp (in Japanese)

Outline

In large plants where heat exchangers are aligned, the heat exchangers and other equipment downwind may take in unexpected hot exhaust mass, which leads to degradation of their performance. This problematic phenomenon is called hot air recirculation (HAR). For practical prediction of HAR occurrence, micro-meteorology and the vortex structure of the turbulent flow generated on the aligned heat exhaust sources are considered to play a key role. Micro-meteorology here means the micro-scale meteorology just above the earth surface strongly affected by artifacts and human activities. By numerically calculating the turbulent flow of the modelled heat exhaust sources, the research group elucidates the HAR-generating mechanism and the dominant parameters while identifying the time-space scale and accuracy required for predicting occurrence. The group also compares the HAR prediction results from micro-meteorological simulations with the data monitored at the factories and calculated results of the heat exhaust source model to verify the feasibility of HAR prediction. Furthermore, the group carries out a verification test of the real-time HAR prediction system using micro-meteorological prediction simulation.

Academic Background and the Core Academic Question

In plants processing natural gas, petroleum, and petrochemicals, heat exchangers, which exhaust a large amount of heat, are often aligned with each other for as long as 500 m. Depending on the weather conditions, the heat exchangers and other equipment downwind take in the heat exhaust from upwind, which leads to degradation of their performance called hot air recirculation (HAR) (Fig. 1). To prevent activation of the emergency shutoff system due to performance degradation and the subsequent production interruption, the factories are often operated below their maximum output. Reduced production due to HAR causes a huge economic loss worldwide. If respective equipment can operate in optimal conditions based on micro-meteorological prediction data and the total production is maximized, we can expect major increases in productivity. Realization of such optimal plant operation requires the elucidation of an HAR-generating mechanism and real-time prediction of its occurrence by meteorological prediction simulation.

To date, an HAR generation mechanism has been studied on virtual plants. JGC Corporation, our collaborating organization for this research task, has also performed an analysis using RANS (Reynolds-Averaged Navier-Stokes), a numerical calculation model for turbulent flow (Fig. 2). In the meantime, as the preliminary study for this research task, our group performed a transient analysis by LES（Large Eddy Simulation）, which has come into common use as its calculation performance improves. This has yielded interesting results that could not be by conventional analysis.

In view of these social and academic backgrounds, we define the “academic questions” in this research as follows: (a) “What are the conditions and mechanisms that generate and maintain the hot air that can cause HAR?”, (b) What are the time-space scale and accuracy of micro-meteorological information required for reproducing HAR phenomena? and (c) Does micro-meteorological simulation meet these requirements? In other words, is micro-meteorological prediction simulation capable of reproducing HAR phenomena?