Experimental Study and Conjugate Heat Transfer Simulation of Turbulent Flow in a 90° Curved Square Pipe

Guanming Guo,Masanobu Koutoku,Keiya Nishida,Ryo Yamamoto,Shinji Sumi,Qiwei Zhang,Hitoshi Hongou,Yuuya Inoue,Hieaki Yokohata,Yoichi Ogata,Masaya Kamigaki

doi:10.3390/en14010094

Guanming Guo, Masanobu Koutoku + Show 9 more

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https://doi.org/10.3390/en14010094

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Abstract

This paper discusses the turbulent flow and heat transfer from a uniform air flow with high temperature to the outside through a 90° curved square pipe. Both conjugate heat transfer (CHT) simulation and experiments of temperature field measurements at cross sections of the pipe are performed. A straight pipe is investigated and compared with the 90° curved pipe. The temperature of the air flow at the inlet of the pipe is set at 402 K, and the corresponding Reynolds number is approximately 6 × 104. To obtain the spatial average temperature at each cross section, the temperature fields are measured along the streamwise of the pipes and in the circumferential direction using thermocouples at each cross section from the inlet to the outlet of both the straight and curved pipes. Furthermore, the simulation is performed for turbulent flow and heat transfer inside the pipe wall using the Re-normalization group (RNG) k-ε turbulence model and CHT method. Both the experimental and numerical results show that the curvature of the pipe result in a deviation and impingement in the high-temperature core and a separation between the wall and air, resulting in a secondary flow pattern of the temperature distribution.

Highlights

Accepted: 23 December 2020In the context of energy conservation and emission reduction, heat exchangers are typically used as coolers and heaters between two or more fluids at different temperatures.Heat exchangers have been widely used in industrial fields, such as refrigeration airconditioning, automobiles, and electricity production
For single-phase fluid flow and heat transfer in pipes, swirl and secondary flow are often used to enhance the heat transfer. This is because the swirl or secondary flow is typically accompanied by a change in the fluid structure, which can promote mixing in the main fluid flow and break the thermal boundary layer
The results showed that turbulence and heat transfer were strongly asymmetric in the curved pipe with higher values near the outer pipe bend

Summary

Introduction

Accepted: 23 December 2020In the context of energy conservation and emission reduction, heat exchangers are typically used as coolers and heaters between two or more fluids at different temperatures.Heat exchangers have been widely used in industrial fields, such as refrigeration airconditioning, automobiles, and electricity production. In an automotive exhaust system, curved pipes are essential components of the exhaust manifold, and the flow and heat transfer characteristics of the curved pipes directly affect the performance of the downstream catalyst. Both the fluid flow and heat transfer in the pipe are important for maintaining the high performance of the close-coupled catalytic converter in automotive engines. For single-phase fluid flow and heat transfer in pipes, swirl and secondary flow are often used to enhance the heat transfer This is because the swirl or secondary flow is typically accompanied by a change in the fluid structure, which can promote mixing in the main fluid flow and break the thermal boundary layer

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