Purpose

The purpose of this study is to analyze the heat transfer and flow enhancement of an Al₂O₃-water nanofluid filling an inclined channel whose lower wall is embedded with periodically placed discrete hydrophobic heat sources. Formation of a thin depletion layer of low viscosity over each hydrophobic heated patch leads to the velocity slip and temperature jump condition at the interface of the hydrophobic patch.

Design/methodology/approach

The mixed convection of the nanofluid is analysed based on the two-phase non-homogeneous model. The governing equations are solved numerically through a control volume approach. A periodic boundary condition is adopted along the longitudinal direction of the modulated channel. A velocity slip and temperature jump condition are imposed along with the hydrophobic heated stripes. The paper has validated the present non-homogeneous model with existing experimental and numerical results for particular cases. The impact of temperature jump condition and slip velocity on the flow and thermal field of the nanofluid in mixed convection is analysed for a wide range of governing parameters, namely, Reynolds number (50 ≤ Re ≤ 150), Grashof number ( 103≤Gr≤5×104), nanoparticle bulk volume fraction ( 0.01≤φb≤0.05), nanoparticle diameter ( 30≤dp≤60) and the angle of inclination ( −60°≤σ≤60°).

Findings

The presence of the thin depletion layer above the heated stripes reduces the heat transfer and augments the volume flow rate. Consideration of the nanofluid as a coolant enhances the rate of heat transfer, as well as the entropy generation and friction factor compared to the clear fluid. However, the rate of increment in heat transfer suppresses by a significant margin of the loss due to enhanced entropy generation and friction factor. Heat transfer performance of the channel diminishes as the channel inclination angle with the horizontal is increased. The paper has also compared the non-homogeneous model with the corresponding homogeneous model. In the non-homogeneous formulation, the nanoparticle distribution is directly affected by the slip conditions by virtue of the no-normal flux of nanoparticles on the slip planes. For this, the slip stripes augment the impact of nanoparticle volume fraction compared to the no-slip case.

Originality/value

This paper finds that the periodically arranged hydrophobic heat sources on the lower wall of the channel create a significant augmentation in the volume flow rate, which may be crucial to augment the transport process in mini- or micro-channels. This type of configuration has not been addressed in the existing literature.

中文翻译：

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纳米流体在带有加热滑移条纹图案的倾斜通道中混合对流和流动增强的两相模型

目的

本研究的目的是分析填充倾斜通道的 Al ₂ O _{3 -}水纳米流体的传热和流动增强，该通道的下壁嵌入了周期性放置的离散疏水热源。在每个疏水加热贴片上形成低粘度的薄耗尽层导致疏水贴片界面处的速度滑移和温度跳跃条件。

设计/方法/方法

基于两相非均质模型分析纳米流体的混合对流。通过控制体积方法对控制方程进行数值求解。沿调制信道的纵向采用周期性边界条件。速度滑移和温度跳跃条件与疏水加热条一起被施加。该论文用现有的实验和特定情况下的数值结果验证了当前的非均匀模型。分析温度跳跃条件和滑移速度对混合对流中纳米流体流动和热场的影响，包括雷诺数 (50 ≤ Re ≤ 150)、格拉肖夫数 ( 103≤Gr≤5×104), 纳米颗粒体积分数 ( 0.01≤φ乙≤0.05）、纳米粒径（ 30≤d磷≤60) 和倾角 ( -60°≤σ≤60°）。

发现

加热条带上方的薄耗尽层的存在减少了热传递并增加了体积流量。与透明流体相比，将纳米流体作为冷却剂可提高传热率以及熵产生和摩擦系数。然而，由于熵产生和摩擦因数的增加，传热的增加率受到了显着的损失幅度的抑制。随着通道与水平面的倾斜角增加，通道的传热性能降低。论文还比较了非齐次模型和相应的齐次模型。在非均匀配方中，纳米颗粒的分布直接受滑动条件的影响，这是由于纳米颗粒在滑移面上的非正态通量。为了这，

原创性/价值

本文发现，通道下壁上周期性排列的疏水热源显着增加了体积流量，这对于增加微型或微通道中的传输过程可能至关重要。现有文献中未涉及这种类型的配置。