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As a new type of fin structure in finned tube heat exchangers, dimple turbulators exhibit excellent potential for thermo-hydraulic performance enhancement. A three-dimensional numerical simulation study was conducted to investigate the influences of five kinds of innovative concave dimple turbulators (CDTs), namelyelliptical dimple, conical frustum dimple, trapezoidal prism dimple, leeward triangular dimple and upward triangular dimple (UwTD) on the thermohydraulic performance enhancement in a plate fin-and-elliptical tube (PFET) heat exchanger, where CDTs are textured on the fin surface transversely between the elliptical tubes. The computational results are analyzed by considering the performance evaluation criterion for the PFET heat exchangers with different types of CDT shapes. The present investigation demonstrates that the heat transfer enhancement is intimately pertained to ejection with longitudinal counter-rotating flow, strengthened secondary flow and vortex structures at the downstream rim of CDT. A parametric study on the CDTs indicated that the UwTD vortex turbulators give better thermo-hydraulic performance under the present conditions. The numerical simulation results illustrated different secondary flow structures and heat transfer characteristics of the CDTs with various shapes, which disclosed the influential mechanisms of differently shaped dimple turbulators on the heat transfer augmentation in PFET heat exchangers.

Three-dimensional numerical simulations are successfully carried out on thermo-hydraulic characteristics of a new plain fin-and-elliptical tube (PFET) heat exchanger with innovative types of tube-banks, namely-a slotted elliptical tube-bank (SETB) (Case B and Case C) and a slotted annular elliptical tube-bank (SAETB) (Case D and Case E). The new PFET heat exchanger contains elliptical cross-sectioned tubes that create narrow slots oriented in the streamwise or/and spanwise direction. The investigation on the effects of different shape tube-banks on the air-side heat transfer and fluid flow characteristics in the new PFET heat exchanger was performed using the ANSYS CFXV R package. The objectives of this investigation are to determine an optimal staggered tube-bank configuration for augmenting heat transfer rates with minimal pressure drop penalties, and compare the results against traditional non-slotted elliptical tube-bank heat exchangers. The averaged heat transfer rate of the SETB/SAETB heat exchanger is more than 15% greater than that of the traditional nonslotted elliptical tube heat exchanger. The overall performance evaluation criteria, estimated in terms of the area goodness factor and volume goodness factor for enhanced cases (SETBs/ SAETBs), were higher than there found by a non-slotted elliptical tube-bank case. Overall, the computational results showed that the Case D causes an appreciable increase of the heat transfer rate without a pressure drop penalty.

Purpose The purpose of this paper is to investigate the numerical fluid-structure interaction (FSI) framework for the simulations of mechanical behavior of new vortex generators (VGs) in smooth wavy fin-and-elliptical tube (SWFET) heat exchanger using the ANSYS MFX Multi-field® solver. Design/methodology/approach A three-dimensional FSI approach is proposed in this paper to provide better understanding of the performance of the VG structures in SWFET heat exchangers associated with the alloy material properties and geometric factors. The Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are applied for modeling of the turbulent flow in SWFET heat exchanger and the linear elastic Cauchy-Navier model is solved for the structural von Mises stress and elastic strain analysis in the VGs region. Findings Parametric studies conducted in the course of this research successfully identified illustrate that the maximum magnitude of von Mises stress and elastic strain occurs at the root of the VGs and depends on geometrical parameters and material types. These results reveal that the titanium alloy VGs shows a slightly higher strength and lower elastic strain compared to the aluminum alloy VGs. Originality/value This paper is one of the first in the literature that provides original information mechanical behavior of a SWFET heat exchanger model with new VGs in the field of FSI coupling technique.