Numerical investigation of the laminar natural convection heat transfer from two horizontally attached horizontal cylinders. (January 2017)

• Record Type: Journal Article
• Authors: Liu, Jie; Liu, Huan; Zhen, Qi; Lu, Wen-Qiang
• Is Part Of: International journal of heat and mass transfer. Volume 104(2017:Jan.)
• Page Start: 517
• Page End: 532
• Publication Date: 2017-01
• Subjects: Numerical investigation -- Natural convection -- Two attached cylinders -- Correlating equation; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2016.08.075
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: A more accurate and effective computational model proposed by Bejan et al. (1995) is applied here. The location of the front stagnation point and the separation point shift with Rayleigh number. The location of the maximum value for the local Nusselt number moves downstream versus a single cylinder. The empirical equation for two attached cylinders has been provided. Abstract: In this work, natural convection heat transfer from two horizontally attached cylinders in air has been studied numerically over the range of Rayleigh number 10 ⩽ Ra ⩽ 10 5 . A new model proposed by Bejan et al. (1995) is applied here, and it has been proved to be a more accurate and effective method for the numerical simulation of the natural convection in free space than other models used previously. Furthermore, the representative results for streamlines, isothermal contours, local Nusselt number and local drag coefficients have been presented with different Rayleigh numbers. It can be observed that there form two recirculation vortexes in the wake region when the two plumes begin to merge, and their sizes grow with the increasing Rayleigh number due to the downstream movement of the front stagnation point and the upstream movement of the separation point. Owing to the interactions of their plumes, the location of the maximum value of local Nusselt number moves downstream along the cylinder surface, i.e., it displaces to 133–150° depending on the Rayleigh number whereas it always occurs at the front stagnation point corresponding to 90° for a single cylinder. However, because the thinnest boundary layer in this work still hardly penetrates the small clearance between them and then influences their heat transfer, their interactions are independent of the Rayleigh number. Finally, a new correlating equation of the average Nusselt number with the Rayleigh number for the present configuration, has been proposed.