Investigation of evaluation criterion of axial wall heat conduction in tube laminar flow and heat transfer

The effect of axial wall heat conduction in circular tube laminar flow and heat transfer has been investigated under constant temperature boundary conditions. Three-dimensional numerical simulations are performed with different wall thicknesses, wall materials, tube lengths as well as a wide Peclet number range from 7 to 7000. Three parameters including the modified axial conduction number (M), the so-called axial conduction number (Mc) and the temperature gradient number (-) are comprehensively studied. Under the thermal boundary condition of constant wall temperature, the temperature gradient number is introduced to evaluate the importance of the axial wall heat conduction.