To analyze conjugate effect under partially heated condition, two-dimensional numerical study is performed for single-phase laminar flow through microtubes. Constant heat flux is applied on outer surface along the heating length of the microtube. For partial heating, the microtube is divided into three parts of 6 mm (L₁), 48 mm (L₂) and 6 mm (L₃). Three cases are considered for partial heating: (a) insulated across L₁ and L₃ and heating across L₂, (b) insulated across L₁ and heating across L₂ and L₃ and (c) insulated across L₃ and heating across L₁ and L₂. For direct comparison, heating across full length of the microtube is also considered. Parametric variations include microtube wall thickness to inner radius ratio (δ_sf), and solid to fluid conductivity, ratio (k_sf) and flow Re. Presence of axial wall conduction is assessed in terms of dimensionless wall temperature and heat flux at the solid–fluid interface, dimensionless bulk fluid temperature, and local and average Nusselt number. The results indicate that there exists an optimal value of average Nusselt number for certain value of k_sf at which dominance of axial wall conduction is smaller. Additionally, to highlight the effect of axial wall conduction, local heat flux distribution at the solid–fluid interface is also explored.

为了分析部分加热条件下的共轭效应，对通过微管的单相层流进行了二维数值研究。沿微管的加热长度在外表面施加恒定的热通量。为了进行局部加热，将微管分为6毫米（L ₁），48毫米（L ₂）和6毫米（L ₃）三个部分。考虑三种情况的局部加热：（a）在L ₁和L _3上绝缘并在L _2上加热，（b）在L ₁两端绝缘并在L ₂和L _3上加热（c）在L ₃两端绝缘，并在L ₁和L ₂两端加热。为了直接比较，还考虑了整个微管的加热。参数变化包括微管壁厚与内半径之比（δ _SF），和固体与流体的导电性，比（ķ _SF）和流动再。轴向壁传导的存在是根据无量纲的壁温和固液界面处的热通量，无量纲的散装流体温度以及局部和平均努塞尔数来评估的。结果表明，对于一定的k _sf值，存在平均努塞尔特数的最优值轴向壁传导的主导地位较小。另外，为了突出轴向壁传导的影响，还研究了固-液界面处的局部热通量分布。