Parametric study of the performance efficiency of a single oil cooler section

The paper presents the results of numerical investigation of the influence of the design parameter - the gap between the cooling plates of the convective heat exchanger for oil cooling on its efficiency. A single cooling section of an oil cooler consisting of cooling plates separated by a certain distance is considered. Each single plate of the oil cooler has 6 internal channels of complex geometry and row external fins, each row of which includes 11 elements of two standard sizes, and the number of rows is determined by the length of the plate. The efficiency of the device is evaluated on the basis of analyzing the change of heat transfer coefficients at the boundaries of working media from the increase of the distance between the plates. The problem of conjugate heat exchange between heated hydraulic oil, oil cooler plates and cold turbulent flow of air blown by a fan is considered. The mathematical model of fluid media motion is based on the Navier-Stokes equations. Modelling of heat transfer processes in the oil cooler plate is based on the heat conduction equation. To close the averaged system of conservation equations, the Menter SST turbulence model is applied. The numerical solution of the obtained system of equations is constructed by the method of control volumes using the chtMultiRegionFoam solver of the freely distributed OpenFOAM software. Numerical modelling of the working processes occurring in a single section of the oil cooler was performed using the establishment method. For discretization of non-viscous flows (in oil and air), a counter flow scheme of 2nd order of accuracy is applied, and for viscous flows, total variation minimization (TVD) schemes and the limitedLinear method were applied. The gradients were approximated based on the linear Gaussian method. The conjugate gradient method was used to accelerate convergence. As a result of numerical modelling, the fields of physical quantities, air and oil flow structure in the corresponding channels of the device were obtained. The influence of the plate gap size on the internal and external aerodynamics of the unit section of the oil cooler is identified and shown. Non uniform heating of the cooling section body with localization of the temperature maximum in the area of internal central channels has been revealed, described and substantiated. The analysis of the obtained thermophysical characteristics allowed to reveal the optimum distance between the plates of the oil cooler of 22 mm.