Purpose

The purpose of this paper is to numerically study the influence of wall conduction on the heat transfer of supercritical n-decane in the active regenerative cooling channels.

Design/methodology/approach

A horizontally placed rectangular pipe with a solid zone and another one without a solid zone were used. A drastic variation of thermo-physical properties was emphatically addressed. After the verification of mesh and turbulence models comparing with the experimental results, a mesh number of 4.5 M and the low Reynolds number SST k-ω turbulence model were chosen. The solution of the governing equations and the acquisition of the numerical results were executed by the commercial software FLUENT 2020 R1.

Findings

The numerical results indicate that there is a heat transfer deterioration (HTD) potential for the upper wall, lower wall and sidewall with the decrease of mass flux. Due to wall conduction, the distribution of the fluid temperature at spanwise-normal planes becomes uniform and this feature also takes advantage of the relatively uniform transverse velocity. For the streamwise-normal planes, the low fluid temperature appears close to the upper wall at the region near the sidewall and vice versa for the region near the centre. Undoubtedly, the secondary flow at the cross-section plays a crucial role in this process and the relatively cool mainstream is affected by the vortices.

Originality/value

This study warns that the wall conduction must be considered in the practical design and thermal optimization due to the sensibility of thermo-physical properties to the heat flux. The secondary flow caused by the buoyancy force (gravity) plays a significant role in the supercritical heat transfer and mixed convection heat transfer should be further studied.

中文翻译：

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壁传导对水平超长管中超临界正癸烷冷却超燃冲压燃烧器的传热特性的影响

目的

本文的目的是从数值上研究壁传导对有源再生冷却通道中超临界正癸烷传热的影响。

设计/方法/方法

使用具有实心区的水平放置的矩形管和没有实心区的另一根矩形管。着重解决了热物理性质的急剧变化。在验证了网格和湍流模型并与实验结果进行比较之后，选择了4.5 M的网格数和低雷诺数SSTk-ω湍流模型。控制方程的求解和数值结果的获取由商业软件FLUENT 2020 R1执行。

发现

数值结果表明，随着质量通量的减小，上壁，下壁和侧壁存在传热恶化（HTD）的可能性。由于壁传导，流体温度在翼展方向法线平面上的分布变得均匀，并且此特征还利用了相对均匀的横向速度。对于垂直流平面，较低的流体温度在靠近侧壁的区域靠近上壁出现，反之亦然，对于靠近中心的区域则相反。毫无疑问，横截面的二次流在此过程中起着至关重要的作用，相对凉爽的主流受到旋涡的影响。

创意/价值

这项研究警告说，由于热物理性质对热通量的敏感性，在实际设计和热优化中必须考虑壁传导。浮力（重力）引起的二次流在超临界传热中起着重要作用，应进一步研究混合对流传热。