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A promising new way of direct conversion of the heat of piston engine exhaust gases into electric energy is investigated. An original design of a thermoelectric converter with various surface reliefs (smooth, spher ical peaks, spherical dimples) is developed. The engine operation and the flow in the heat exchanger of the ther moelectric generator are modeled. Based on the results of 3D modeling of convective heat transfer, it has been determined that the surface with heat transfer intensifiers in the form of spherical dimples is the most efficient.

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Reliable information on the distribution of average velocities in the cross section of a turbulent flow are required to solve a number of practical problems. A more successful solution of this problem is achieved by using semi-empirical theories of turbulence, for example, the Prandtl theory. Prandtl schematized uniform isotropic turbulent flow in a pipe in the form of a thin "laminar" sublayer near the walls, where movement is caused exclusively by the action of viscosity forces, and the "core of the flow," within whose bounds the effect of viscosity can be neglected. An important conclusion drawn by Prandtl is the relation between the absolute magnitude of the stress T of the turbulent flow and the gradient of the average velocity in the core of the turbulent flow in the following form: 2 ,.l=.,.(w ).where s is the run path of the fluid particles, which is dictated by turbulent pulsations, assumes a linear dimension, and is called the long path of agitation by Prandtl, and 0 is the density of the fluid.To derive the velocity distribution across the active section of the pipe, Prandtl makes two assumptions, which are correct only for a narrow region situated near the wall itself: the tangential stress is constant and is equal to the tangent stress at the wall, i.e.,and, the path of agitation is proportional to the distance from the wall, i.e~where m is a universal constant (~=0A).Using (2) and (3) (6) Solution (6) is the so-called logarithmic velocity distribution, which Prandtl proposed for the core of a turbulent flow. For the axis of the flow, we have: y = r, and u = Umax; consequently, it is possible to write ~= l--Inr+C, ., ~