동심 환형 파이프 내부 난류 회전 유동에서 대류 열전달 현상의 RANS 분석

초록

This study aims at investigating the heat transfer characteristics of turbulent swirling flows inside annular pipes. For turbulent swirling flows with the inlet Reynolds number of 8,000 and inlet swirl number of 1, unsteady RANS simulations using the Reynolds stress model are performed to examine the effects of the ratio of the inner and outer radii (i.e., gamma), Prandtl number (Pr), and different wall temperature conditions on the streamwise profiles of the swirl number and cross-sectional mean temperature. It was observed that the cross-sectional mean temperature cooling rate (CMTCR) decreases as Pr increases. The heat transfer rate through the inner wall is affected more strongly by gamma compared to the outer wall. The existence of an optimal gamma value that minimizes CMTCR is found to be more pronounced as Pr increases or for heat transfer through the outer wall. As a previous study found the existence of an optimal gamma value that minimizes the swirl decay rate (SDR), the present results imply that the Reynolds analogy between SDR and CMTCR holds better as Pr increases. It is deduced that the analogy is compromised as Pr decreases because the effect of the molecular diffusion becomes stronger.

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