CFD investigation of the intensity of heat transfer at forced convection of preheated air in a steel pipe

This paper presents a CFD investigation in ABAQUS of the heat exchange intensity in curvilinear and linear zones of a steel pipe through which preheated air is flowing. The process intensity has been compared based on the average cross-section temperature differences. The research has been implemented as a continuation of a simulation study of the heat convection process in the pipe, as a result of which the temperature distribution of the fluid has been obtained, and the internal coefficient of convection heat exchange has been calculated. The external coefficient of convection heat exchange and the coefficient of overall heat exchange have been determined by ignoring the thermal resistance of the pipe wall. Heat exchange processes realized at three fluid velocities have been investigated. The impact of the fluid velocity on the intensity of the heat transfer process in the initial curvilinear zone of the pipe, on the values of the outer coefficient of heat convection and on the overall heat exchange coefficient, have been investigated. It has been found that the total decrease in velocity of $18.98 \%$ resulting in a decrease in the ratio of temperature differences in the two zones by $8.21 \%$. In the first range of speed change, $6.16 \%$ decrease in velocity leads to 6.04 $\%$ raise in the external heat convection coefficient and $2.30 \%$ raise in the coefficient of overall heat exchange. In the second velocity range, $13.66 \%$ decrease in velocity results in $16.72 \%$ decrease in the external heat convection coefficient and 14.79 $\%$ decrease in the overall heat transfer coefficient.