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• Validation of numerical models is presented by comparison with experimental results. • Influence of turbulence Prandtl number model and turbulence model is analyzed. • Effects of structural parameter on thermal hydraulic performances are discussed. • Effects of flow parameter on thermal hydraulic performances are analyzed. Sodium-cooled fast reactor coupled with supercritical CO 2 Brayton cycle has broad development prospects owing to the high thermal efficiency, smaller components and compact footprint. As one of the key components, sodium-supercritical CO 2 compact heat exchanger plays a vital role in improving the operation performance of coupled power systems. In this paper, a numerical model for coupling heat transfer of sodium-supercritical CO 2 in a straight-channel compact heat exchange channel is established and the prediction accuracy of the model is verified with experimental results. The influence of structural parameters and flow parameters on the resistance characteristics and heat transfer performance of cold and hot channels is systematically analyzed. The results show that the structure of semi-circular cross-section with an ABAB layout performs best in heat transfer performance. For the sodium channel, performance evaluation criteria gradually grow with the increase of sodium inlet velocity and slowly decline with the supercritical CO 2 inlet velocity. For the supercritical CO 2 channel, performance evaluation criteria decrease with the increase of sodium inlet velocity and increase with the supercritical CO 2 inlet velocity. Reducing the supercritical CO 2 inlet temperature could effectively improve the thermal hydraulic performance of the sodium-supercritical CO 2 compact heat exchange channel. [ABSTRACT FROM AUTHOR]

• Compound porous media model is proposed to simulate performance of U-tube HX. • The complicated U-tube bundle is divided into three porous media sections. • For each section, porous coefficients are obtained from empirical correlations. • Results of compound porous media approach are in good agreement with test results. • The proposed model shows the ability to correctly model a complex geometry HX. This paper describes a compound porous media model approach for numerical analysis to investigate the aero-thermal performance and characteristics of a flat top U-tube heat exchanger. The heat exchanger was considered as a combination of three sections; vertically straight tube section, bent tube section, and horizontally straight tube section. The porous media coefficients were obtained by using empirical correlations for the pressure drop and heat transfer for each section. The numerical results of the compound porous media model were compared to those of a conjugate heat transfer (CHT) CFD analysis, considering real tube geometry and experiments in order to validate the proposed compound porous media approach. The validation revealed that the proposed approach provides reasonable flow and heat transfer characteristics as well as the overall aero-thermal performance of the flat U-tube heat exchanger, with a considerable reduction of the required computational power. [ABSTRACT FROM AUTHOR]

• This paper proposes an approach for design and optimization of heat exchangers. • This paper discusses heat transfer enhancement of heat exchangers. • This investigates the effect of baffles and tubes in heat transfer performance. • This work studies the fluid flow behavior within a heat exchanger. • This presents on how CFD can be useful in heat exchanger design. Heat transfer is one of the key aspects of machineries, devices and industrial processes for maintaining their functionality and also for achieving better product quality. Hence, heat exchangers of different types and sizes are used in these applications with the purpose of removing the extra process/device heat to maintain the desirable working temperatures. However, the size of a heat exchanger is a major consideration for any type of process/device as it decides the space requirements (i.e., the size) of the machine/device or the processing plant. At first, this study aims to investigate the design procedure of a heat exchanger theoretically and then its performance will be analyzed and optimized using computational fluid dynamics. For the design purposes, a counter flow heat exchanger was considered and its length was theoretically calculated with the LMTD method while the pressure drop and energy consumption were also calculated with the Kern method. Afterwards, a computational model of the same heat exchanger was implemented with ANSYS and then this model was extended to six different models by altering its key design parameters for the optimization purposes. Eventually, these models were used to analyze the heat transfer behavior, mass flow rates, pressures drops, flow velocities and vortices of shell and tube flows inside the heat exchanger. Theoretical and CFD results showed only a 1.05% difference in terms of the cooling performance of the hot fluid. The axial pressure drops showed positive correlations with both the overall heat transfer coefficient and pumping power demand. Overall, the results of this study confirms that CFD modelling can be promising for design and optimization of heat exchangers and it allows testing of numerous design options without fabricating physical prototypes. [ABSTRACT FROM AUTHOR]

Abstract: An experimental and theoretical investigation of the utilization of finned tube compact heat exchanger for a heat recovery steam generator (HRSG) to recover both sensible and latent heat is presented in this paper. The heat transfer and pressure drop characteristics of the fin-and-tube heat exchanger are theoretically studied. A correlation of the combined convection–condensation heat transfer is derived by using the heat and mass transfer analogy models. The experimental results have shown that the Colburn factor (j) and the friction factor (f) for humid air, simulating the exhaust of HRSG, are larger than those for dry air. It has been also found that the f factor difference between humid air and dry air decreases as the air side Reynolds number increases and both the f factor and the j factor for humid air increase with the increase of water vapour concentration. A scheme for the design of compact heat exchanger for HRSGs is presented. [ABSTRACT FROM AUTHOR]