A numerical analysis of heat transfer in a cross-current heat exchanger with controlled and newly designed air flows

Abstract

Simulations of heat transfer between air and flue gases in a plate heat exchanger are presented. The device was designed for the heating of the air supplying a fluidised furnace for the combustion of wet sludge and wood crumbs. The locations of inlets and outlets and the geometry of the heat exchanger are determined by the construction of the furnace. The aim of the simulations was to increase effectiveness of heat transfer through the use of flow redirections with additional baffles placed in the air chamber. The results of the simulations showed that a substantial part of the heat exchanger without baffles is not used effectively. On the basis of a velocity profile, a temperature distribution and a wall heat flux, the geometry of the inter-plate space within the air chamber was modified by adding baffles. The unmodified exchangers had 77% efficiency in comparison to counter-current exchangers with the same heat transfer area. After the application of baffles, the efficiency increased to 83-91% depending on the construction used (one, two or three baffles). The best model variant of the exchanger with baffles led to the increase in the temperature of air supplying the fluidised bed by approximately 76 K in relation to the system without baffles . Unexpectedly, the presented modifications of the geometry of the system had very low influence of the flow resistance in the air chamber. The value of Δp for the system without baffles is almost the same as for the best model variant.

Numerical conformal mapping method vs. geometrical separation attitude: Combustion motor chamber internal flow simulation

“…Modeling the flow behavior inside the combustion chamber using different numerical method is an important issue in the physical (aerospace and mechanical engineering) and mathematical (algebra and numerical methods of complex and bluff‐body) [1–28] contexts. Current problem concerns with a steady‐state two‐dimensional reaction between fuel and oxygen that enters from two different parallel locations openings (inlets) through combustion process that was modeled by coupled flow field and mass distribution subjected to the influence of a local discrete vortex.…”

“…Although coupled to mass (fraction) concentrations difference ( m ) that expressed in Equation () and appropriate to Refs. [4–9] that are also varying in the two‐dimensional medium (although the used different coordinates system). Also, boundary conditions that are suitable to the mass concentration and stream function appear in Equation () presented in Refs.…”

“…Also, boundary conditions that are suitable to the mass concentration and stream function appear in Equation () presented in Refs. [1–9].…”