1 Copyright © 2012 by ASME Proceedings of the ASME 2012 Summer Heat Transfer Conference HT2012 July 8-12, 2012, Rio Grande, Puerto Rico HT2012-58067 GENETIC ALGORITHM OPTIMIZATION OF A COMPACT HEAT EXCHANGER MODELED USING VOLUME AVERAGING THEORY David Geb Feng Zhou George DeMoulin Ivan Catton University of California, Los Angeles Henry Samueli School of Engineering and Applied Science Department of Mechanical and Aerospace Engineering Los Angeles, California, U.S.A. ABSTRACT This paper proposes and implements a new methodology for optimizing Compact Heat Exchangers (CHXs) using a Volume Averaging Theory (VAT) model and a Genetic Algorithm (GA) optimizer. This method allows for multiple- parameter optimization of CHXs by design of their basic morphological structures, and is applied to a Finned-Tube Heat Exchanger (FTHX). A consistent model is used to describe transport phenomena in a FTHX based on VAT, which allows for the volume averaged conservation of mass, momentum, and energy equations to be solved point by point, with the morphology of the structure directly incorporated into the field equations. The equations differ from known equations and are developed using a rigorous averaging technique, hierarchical modeling methodology, and fully turbulent models with Reynolds stresses and fluxes in the space of every pore. These averaged equations have additional integral and differential terms that must be dealt with in order for the equation set to be closed, and recent work has provided this closure. The resulting governing equation set is relatively simple and is discretized and solved using the finite difference method. Such a computational algorithm is fast running, but still able to present a detailed picture of the temperature fields in both of the fluid flows as well as in the solid structure of the heat exchanger. A GA is integrated with the VAT-based solver to carry out the FTHX optimization, which is a ten parameter problem, and the FTHX’s effectiveness is selected as the fitness function to be optimized. This method of using the VAT-based solver fully integrated with a GA optimizer results in an all-in-one tool for performing multiple-parameter constrained optimization on FTHXs. INTRODUCTION Despite the crucial role of heat exchangers in industrial installations, there is still a great deal of empiricism in their design. Although current guidelines provide an ad-hoc solution, a unified design approach based on simultaneous modeling of the thermal-hydraulics and thermal-structural behavior has not been proposed beyond direct numerical simulation-based methods. As a consequence, designs are often overly constrained with a resulting economic penalty. It is apparent that a more scientific procedure for the design and optimization of heat exchangers is needed. Previous work has shown that flow and heat transfer in Compact Heat Exchangers can be treated as phenomena in highly heterogeneous structures and that their behavior can be properly predicted with porous media modeling through applying VAT to the Navier-Stokes and thermal energy equations for both the fluid and solid phases. Derivation of the VAT-based equations governing momentum and heat transport in highly heterogeneous media is based on averaging the transport equations in both the fluid and solid phases of the heterogeneous medium over a certain REV (see, for example Whitaker [1-3] for laminar regime developments and Shcherban et al [4], Primak et al. [5], and Travkin and Catton [6, 7] for turbulent regime developments). Such VAT-based modeling directly incorporates the medium morphology characteristics into the governing field equations. Using different flow regime transport models and second order turbulent models, equation sets are obtained for turbulent momentum transport and two- and three-temperature heat transport in non-isotropic heterogeneous CHE media while accounting for inter-phase exchange and micro-roughness. The equations differ from those