Heat transfer and gas dynamics numerical modelling of compact pipe bundles of new design

Abstract

Weight and size characteristics, heat transfer efficiency across the surface, pressure losses in the flow paths for each heat transfer medium, and other parameters that characterise the heat exchanger play an important role in the development of new types of heat exchanger designs. This predefines the research relevance and the need for a solution. The research aims to develop and implement fundamentally new approaches to the design parameters of shell-and-tube heat exchangers, in which smooth-tube bundles are placed as compactly as possible in their crossflow. For this purpose, numerical modelling in the heat exchanger channels and studies of heat transfer and gas dynamics were carried out. The ANSYS Fluent software package was used to calculate the hydrodynamics and heat transfer in the tube bundle channels. Numerical modelling of hydrodynamics and heat transfer processes in the flow of a compact bundle of small-diameter pipes was carried out. The mathematical model includes the Navier-Stokes equation, the energy equation, and equations describing the turbulence of the external flow. The turbulence model was chosen as a model that describes turbulence in channels well. The results of numerical modelling showed a compact bundle of pipes at the outlet of the channels, with an average value of +20.1ºС. Notably, the local temperature values near the channel walls are close to +30 °C. The air velocity at certain points of the duct reaches 85.1 m/s. At the same time, the average air velocity in the cross-section of the channel is about 41.2 m/s at Re=21420. It is demonstrated that the maximum values of local heat transfer coefficients for pipes in a compact bundle are observed in the areas where the flow joins the pipe surface and at the beginning of the boundary layer formation. The maximum values of the heat transfer coefficient reach up to 1335.5 W/m2·ºС for the second and third rows, and at the front point of the first order, it is 1042.3 W/m2ºС. These results will improve the weight and dimensions of shell-and-tube heat exchangers and reduce their cost