Unsteady Convective Heat Transfer in Channels

Mathematical Modeling of Flow and Heat Exchange in Pipes with Surface Turbulators with a Square Cross-Section (S/H = 1) and Edges (S/H << 1) Based on the Low-Reynolds Mentor Model

“…For the external flow around rectangular protrusions, a similar approach was applied, for example, in Ashrafian A [14]. The main direction of this work can be briefly characterized as follows: to carry out calculations of local and averaged parameters of flow and heat transfer in pipes with surface narrow turbulators in the form of a rib (s/h << 1; s is the width of the turbulizer, h is the height of the turbulizer) for relatively a wide range of channel geometry and coolant flow modes (Re = 104 ÷ 105; Pr = 0.72 ÷ 10; d/D = 0.98 ÷ 0.90; t/D = 0.25 ÷ 1.00); carry out an exhaustive analysis of the data obtained, focusing on the comparative analysis of the calculated data with the corresponding data for pipes with turbulators of square cross-section (s/h = 1), obtained in the framework of this work, as well as in Dreitser GA, Lobanov IE, Bystrov YuA, Ashrafian A [3-9,11-13,15-17], which were previously verified by the existing experiment [1,2], as well as by data from other theoretical approaches [6][7][8][9]; the comparative analysis should reveal the advantages and disadvantages of the above-mentioned narrow and wide turbulators, all other things being equal.…”

“…A well-known and very well-tested in practice method of vortex intensification of heat transfer is the application of periodic protrusions on the walls of the washed surfaces [1]. The study of the structure of the intensified flow is mainly carried out by experimental methods [1,2], while modern computational works on this topic are relatively few [3][4][5][6] and are only partially devoted directly to the structure of the intensified flow; some of the methods (eg, a certain part of the works [6][7][8][9] use only integral approaches to this problem. Recently, multi-unit computational technologies have been intensively developed for solving problems of vortex aeromechanics and thermal physics, based on intersecting structured grids.…”

Two centuries of the thermal regenerator

“…Transformation is via the de®nitions of and . Reference to equations (10) and (11) will show that a range of values of and =u leads to the same . Likewise, is constant for any combination of NTU, N FL =p and u for which the group pu=(NTU N FL ) keeps the same numerical value.…”

“…In equations (10) and (11) Kalinin and Dreitser [10] have discussed an alternative form of solution obtained by Laplace transformation. The aesthetic appeal of the`analytical' solution is tempered somewhat by the realities of retrieving the temperature solutions, an essentially numerical task, and, even with the aid of the computer, not trivial.…”

Analysis of the gas turbine rotary regenerator

“…The alternative approach of Hausen's contemporary, Nusselt (20) involved pursuing solution analytically as far as integral expressions involving Bessel functions of imaginary arguments. More recent approaches to equation (29) [Kalinin and Dreitser (11)] tend to be based on Laplace transformation. This leads directly to solution in terms of integral expressions equivalent, for comparable initial conditions, to those obtained by Nusselt.…”