Impact of the extended computational domain at inlet and outlet on natural convection in a vertical rectangular channel.

• The effects of different geometrical parameters on flow and heat transfer in the extended domain are studied. • The influence of the extended domain is explained from the angle of relative pressure and pressure gradient. • The criterion for judging the accuracy of numerical simulation results of the extended domain is put forward. • The optimal geometric parameters of the extended domain are selected. The natural convection flow in the vertical rectangular channels is frequently encountered in many engineering applications. Currently, most relevant simulation studies neglected the influence of the extended domain on the calculation results, it could cause the heat transfer coefficient to deviate by more than 10% from the actual result. This paper aims to study the influence of the extended domain on the natural convection heat transfer in a vertical rectangular channel. It is found that the mass flow rate in the channel can rise by approximately 8% and the heat transfer coefficient by up to 13.5% with an increase in the extended domain. This influence is explained from the angle of relative pressure and pressure gradient. The influence of different geometric parameters on the extended domain and the selection of the optimal geometric parameters of the extended domain are discussed. Furthermore, it is expanded to different heated boundary conditions and geometric structures of the channel. This study provided a reference for the selection of extended domains in the corresponding natural convection. [ABSTRACT FROM AUTHOR]