Computer simulation of flows in flat channels
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Abstract
The article deals with the study of transfer processes in an economical indirect evaporative air cooler. The principle of operation of the proposed air cooler is the use of the effect of evaporative cooling. Water (fresh or sea) is a consumable working agent. Evaporative air coolers are characterized by low cost and low operating costs. The cooler matrix is organized by a system of slotted channels. For the manufacture of nozzles, cheap, environmentally friendly and common materials are used: plates or films based on polyethylene, polystyrene or polypropylene and porous non-woven materials based on polypropylene or cellulose (non-woven). The organization of computer simulation of heat and mass transfer in a system of flat channels of a complex (in plan) profile with a small gap, which is 15–50 times smaller than the channel width, is described. As a mathematical model, a system of equations is adopted: continuity, Navier - Stokes in the projection onto the coordinate axes, pressure and Fourier-Kirchhoff.
To simplify the formulation of the problem, a method of averaging the value of the velocity over the third coordinate (over the gap in the channel) is proposed. Averaging is carried out taking into account the velocity profile. Thus, the transition from a three-dimensional to a two-dimensional mathematical model is carried out. To solve the resulting system of equations, a modified difference solution method was used. In this case, an approximation by a three-point scheme is used simultaneously for the terms of the equation with the second and first derivatives. Expressions for the coefficients of the approximating formula are obtained by the method of analytical solution. The scheme is absolutely stable. There are two problems in computer simulation. One is the joint solution of the continuity and Navier-Stokes equations. The second calculation of the pressure field. An iterative coordination of solutions to determine the fields of pressures and flow rates is carried out. Research was carried out on the functioning of an air cooler assembled according to the cross-current circuit (Munters circuit). The organization of a full-scale experiment on an air cooler model is described. The results of full-scale and computational experiments carried out by the authors are presented. There is good agreement between the experimental results.
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References
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