Calculation of Heat Transfer and Drag in Tubes under Conditions of Laminar Flow of Gases with Varying Properties

A numerical investigation is performed of the problem on heat transfer and hydraulic drag in the hydrodynamic and thermal initial sections of a round tube heated by the $q_w = \text{const}$ law, under conditions of laminar flow of gases with varying physical properties. Monatomic, diatomic, and polyatomic gases and gas mixtures are treated, as well as the range of heat loads $Q^+_{in}$ up to $20$. The obtained results are used to analyze disagreement between the available literature data; methods are suggested for improving the engineering procedure of thermohydraulic design under laminar flow of gases and the known model of stabilized flow and heat transfer.