MATHEMATICAL LOW-REYNOLDS MODELING OF HEAT EXCHANGE IIN TURBULENT FLOW IN FLAT CHANNELS WITH TURBULATORS SYMMETRICALLY LOCATED ON BOTH SIDES
Authors: Lobanov I. E. 
Published: December 2018

ObjectivesThe aim of the study was to simulate the heat transfer in flat channel with turbulators, symmetrically located on its both sides, depending on the channel's geometric parameters and the coolant flow modes followed by the verification of the obtained calculated data by the existing experiment.

MethodsThe calculation was carried out on the basis of a theoretical method based on the solution of the Reynolds equations, closed with the help of the Menter shear stress transport model, by factored finite-volume method, as well as the energy equation on multiscale intersecting structured grids (Fast COmposite Mesh method, FCOM).

ResultsA theoretical mathematical calculation model for intensified heat exchange in turbulent flow for a flat channel with turbulators, symmetrically located on both sides, depending on the channel's geometric parameters and coolant flow modes was generated. The calculation results of the intensified heat exchange in flat channels with double turbulators, depending on the determining parameters, are in very good agreement with the existing experimental material and have an undeniable advantage over the latter, since the assumptions made in their derivation cover a much wider range of determining parameters than the limitations of the experiments (Pr = 0.7 ч 100; Re = 103ч 106; h / dЭ= 0.005 ч 0.2; t / h= 1 ч 200).

 ConclusionAccording to the calculation results based on the developed model, it is possible to optimise the heat exchange intensification in flat channels with double turbulators, as well as to control the process of heat exchange intensification. The comparative calculations of the intensified hydraulic resistance and heat exchange for flat channels with two-sided symmetrical flow turbulators with corresponding data for round channels with turbulators were carried out and analysed. From the point of view of heat exchange intensification, all other conditions being equal, the reduction of a flat channel with two-sided symmetrical turbulators with respect to a round tube with turbulators takes place because a smaller increase in heat exchange is achieved with a greater increase in hydraulic resistance. It was established by calculation that the relative hydraulic resistance ξП/ ξT for channels with turbulators is always higher than for smooth channels; however, the relative heat exchange NuП/ NuT for channels with turbulators can be higher than for smooth channels. Therefore, there is an enhanced redistribution of the temperature drop over the channel section with an intensified heat exchanger. The developed theoretical method based on the solution of the Reynolds equations by the factored finite-volume method, combined with the energy equation on multiscale intersecting structured grids and closed by means of the Menter shear stress transport model, makes it possible, with reasonable accuracy, to calculate heat exchange coefficients and hydraulic resistance in flat channels of practically any forms of double symmetrically located flow turbulators.