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The study aimed to investigate the heat transfer (HT) properties of a tubular heat exchanger (HX) by using innovative baffle plate arrangements. The newly designed baffle plate was circular with triangular openings and adjustable triangular flow deflectors. These deflectors were strategically placed at the inlet of the HX to create a swirling flow downstream. Three baffle plates were installed along the flow direction with different length‐to‐diameter ratios (pitch ratios) to assess their impact on HT, pressure drop, and thermal enhancement factor. The study compared these results with a smooth channel under varying Reynolds numbers (16,500–29,500). The findings revealed that both the pitch ratio (0.6–1.2) and the inclination angle of the deflectors (30⁰–50⁰) significantly affected the HX's performance. Notably, the baffle plate with a deflector inclination angle of 30° and a pitch ratio of 1 showed a remarkable average improvement of 36.5% compared to other angles and ratios. [ABSTRACT FROM AUTHOR]

In this study, extensive research was conducted using computational fluid dynamics (CFD) ANSYS®–FLUENT, with the k–ε turbulence heat transfer module to optimize the rifled‐tube heat exchanger through parametric modifications for heat transfer and Goodness factor enhancement. This is based on predicting the performance of various heat transfer surfaces such as rectangular and two opposite right‐angled triangular ribs. The objective of this research was to enhance the heat transfer efficiency of a rifled tube with rectangular ribs, a height of 0.775 mm, and helix angles of 30° and 58°. The research findings demonstrated that the heat transfer rate improved owing to the establishment of a secondary helical or swirl flow near the wall region, leading to an enhanced heat transfer. The modification of the rib geometry from rectangular to two opposite right‐angled triangles increased the heat transfer by 17%, whereas the pressure drop remained relatively constant at 0.62 mm of rib height. This benefit is directly translated into heat transfer without any change in pressure drop. The values of the friction factor (f), Nusselt number (Nu), and goodness factor are appropriate for the new geometry in relation to the reference geometry. Rifled‐tube designers can use CFD heat transfer analysis to optimize the design, reduce the need for physical prototypes, and test similar applications and rib configurations. [ABSTRACT FROM AUTHOR]

An exploratory investigation was conducted to analyze a tubular heat exchanger's turbulent heat transfer characteristics using an innovative baffle plate design. The design incorporated a perforated conical baffle plate and an adjustable rectangular deflector. The strategic placement of this baffle plate at the heat exchanger inlet facilitated a swirling flow downstream. To assess the impact of this design, three baffle plates with varying pitch ratios (l/D) were positioned in the direction of the flow. The study examined the effects of pitch ratio (ranging from 0.6 to 1.2), deflector inclination angle (ranging from 30° to 50°), and Reynolds numbers (ranging from 16,500 to 29,500). Moreover, the size of the conical baffle plate (H/D) was altered (from 0.25 to 0.15). The findings highlighted the substantial influence of pitch ratio, inclination angle, and height ratio on the heat exchanger's performance. Notably, the configuration featuring an inclination angle of 50° and height ratio of 0.15 exhibited an average performance improvement of 22% compared to other height ratios, inclination angles, and pitch ratios. [ABSTRACT FROM AUTHOR]

The convective mode of heat transfer is mainly due to the bulk motion of the fluid. Its turbulent nature and enhanced heat transfer coefficients have always attracted the academic, scientific community, and industrialists for many decades. The current research is based on the experimental and theoretical investigations on the turbulent convective heat transfer in swirling (60–300 rpm) steam (1–3 bars) injection into cocurrently flowing water. An exponential increase in the convective heat transfers up till the most swollen part of the swirling steam‐water volume of fluids has been observed. However, the convective heat transfer of the remaining part of the steam's plume shows an almost stagnant decreasing trend. The range of Rayleigh number that supports the transition in trends of the convective heat fluxes is 2.84 × 1011–3.71 × 1011. This transition affects the magnitude of the convective heat fluxes and the extent of the effective momentum fluxes, which is evident in the dominant role of the flow instabilities acting across the length of the steam's plume. Computational Fluid Dynamic analysis also has supported the exhibition of the heat fluxes magnitudes under the influence of the interacting Kelvin–Helmholtz instabilities and inertial instabilities across and along with the cocurrently acting shear layer. [ABSTRACT FROM AUTHOR]

Magnetohydrodynamic flow and heat transfer in an ionic viscous fluid in a porous medium induced by a stretching spinning disc and modulated by electroosmosis under an axial magnetic field and radial electrical field is presented in this study. The effects of convective wall boundary conditions, Joule heating and viscous dissipation are incorporated. The governing partial differential conservation equations are transformed into a system of self‐similar coupled, nonlinear ordinary differential equations with associated boundary conditions. The Matlab bvp4c solver featuring a shooting technique and the fourth‐order Runge–Kutta–Fehlberg method are used to numerically solve the governing dimensionless boundary value problem. Multivariate analysis is also performed to examine the thermal characteristics. An increase in rotation parameter induces a reduction in the radial velocity, whereas it elevates the tangential velocity. Greater electrical field parameter strongly damps the radial velocity whereas it slightly decreases the tangential velocity. Increasing magnetic parameter also damps both the radial and tangential velocities. An increment in electroosmotic parameter substantially decelerates the radial flow but has a weak effect on the tangential velocity field. Increasing permeability parameter (inversely proportional to permeability) markedly damps both radial and tangential velocities. The pressure gradient is initially enhanced near the disk surface but reduced further from the disk surface with increasing magnetic parameter and electrical field parameter, whereas the opposite effect is produced with increasing Joule dissipation. Increasing magnetic and rotational parameters generate a strong heating effect and boost temperature and thermal boundary layer thickness. Nusselt number is boosted with increasing Brinkman number (viscous heating effect) and Reynolds number. The simulations are relevant to electromagnetic coating flows, bioreactors and electrochemical sensing technologies in medicine. [ABSTRACT FROM AUTHOR]

This paper numerically investigates both the inline and staggered arrays of circular multiple swirling air jets that impinge perpendicularly onto a smooth flat surface. The simulations were conducted for various flow and geometric parameters, such as Reynolds number (Re = 11,600, 24,600, and 35,000), jet‐to‐surface distance (H/D = 1, 2, 3, and 4), jet‐to‐jet separation distance (Z/D = 1.5, 3.0, and 4.5) and swirl numbers (S = 0, 0.3, and 0.75), where D is the nozzle diameter. For S = 0.75, a strong recirculation develops due to the vortex breakdown, depends on Z/D, around the axis and near the wall. The extent of the recirculation is larger for the staggered array. Intense heat transfer is anticipated at strong swirl and close impingement cases with the expense of uniformity; whereas a relatively even heat transfer is observed for larger impingements. The increase in jet‐to‐jet separation enhances the overall cooling effect and the staggered configuration of nozzles gives better performance. It appears that both the crossflow and turbulence around the periphery of each jet predominantly govern the heat transfer characteristics. The enhancement of heat transfer occurs for increasing Re, and the overall Nusselt number (Nu) prediction is scaled by Ren, with n dependent on S. Finally a correlation is developed for the average Nusselt number to relate different control parameters. [ABSTRACT FROM AUTHOR]

This paper examines experimentally the effect of jet vortex technology on enhancing the heat transfer rate within a double pipe heat exchanger by supplying the heat exchanger with water at different vortex strengths. A vortex generator with special inclined holes with different inlet angles was designed, manufactured, and integrated within the heat exchanger. In this study, four levels of Reynolds number for hot water in the annulus (Reh) were used, namely, 10,000; 14,500; 18,030; and 19,600. Similarly, four levels of Reynolds number for cold water in the inner tube (Rec) were used, namely, 12,000; 17,500; 22,500; and 29,000. As for the inlet flow angle (θ), four different levels were selected, namely, 0°, 30°, 45°, and 60°. The temperature along the heat exchanger was measured utilizing 34 thermocouples installed along the heat exchanger. It was found that increasing the inlet flow angle (θ) and/or the Reynolds number results in an increase in the local Nusselt number, the overall heat transfer coefficient, and the ratio of friction factor. It is revealed that the percentage increase in the average Nusselt number due to swirl flow compared to axial flow was 10%, 40%, and 82% for an inlet flow angle of 30°, 45°, and 60°, respectively. [ABSTRACT FROM AUTHOR]

To reduce the heat exchanger's costs in a highly competitive industry, thermal performance enhancement of the heat exchangers has successfully gained attention in the last few decades. Among different engineering approaches, the application of the enhanced pipes provides a key solution to improve heat performance. In this paper, the investigation develops a numerical study based on the commercially available computational fluid dynamics codes on the turbulent flow in three‐dimensional tubular pipes. Various concavity (dimple) diameters with corrugation and twisted tape configurations are investigated. The study has shown that perforated geometrical parameters lead to a high fluid mixing and flow perturbation between the pipe core region and the walls, hence better thermal efficiency. Moreover, a model of concavity (dimple) with a 4 mm diameter allows the highest heat transfer enhancement among other designs. In addition, the study shows that due to the disturbance between the pipe core region and the pipe wall, the transverse vortices and swirl flow generated are forceful, which leads to better heat transfer enhancement compared with the conventional (smooth) pipes. As the Reynolds number (Re) rises, the mixing flow, secondary, and separation flow extend to become higher than the values in a smooth pipe, allowing a higher value of performance evaluation factor to be achieved for a dimple diameter of 1mm at the low Re values. This study, therefore, shows the promising potential of the enhanced pipes in the heat transfer enhancement of heat exchangers that is crucial in industrial applications to save more energy. [ABSTRACT FROM AUTHOR]

The precise prediction of the aerothermal conditions at the outlet of modern combustors of aero engines is of primary interest in the aerothermal design of high‐pressure turbines. The use of high swirling flows to stabilize the flame in the new generation of lean‐burn combustors (LBCs) leads to shorter combustor length and high degrees of unsteady temperature. These aspects generate high levels of turbulence and complex temperature nonuniformity patterns at the combustor–turbine interface. Therefore, the nozzle guide vane (NGV) located at the interface exhibits a high inlet temperature gradient called a hot‐streak. The transport mechanism of the hot‐streak across the NGV needs to be decrypted to increase turbine service life and enhance its performance. In this context, the present study aims to examine numerically the effect of three new distorted hot‐streak gradients on the heat transfer characteristics across a turbine NGV. An innovative LBC is used to generate the three inlet hot‐streaks, which are highly swirled and distorted similar to real aero‐engine conditions. The use of such a generation approach avoids any simplification associated with uniform or circular contours that are widely used by researchers. A solid NGV cascade developed by NASA is adopted for the investigations. The results show significant differences in the thermal field on the cascade at each distorted thermal condition. The transport of the hot‐streak behaves differently under axial and swirl conditions. The presence of a swirl induces flow mixing and results in thermal load increasing on the cascade surfaces (NGV, hub, and shroud). [ABSTRACT FROM AUTHOR]

The rate of heat transfer in helical pipes is much more than straight pipes. In the present study, heat transfer and fluid flow in a double-coil heat exchanger with an innovative swirl generator with a curved structure in the inner channel (hot side) are studied, numerically. The proposed turbulator has a curved structure and 12 blades to produce swirl flows. Also, two holes are considered at the semi-conical part of the turbulator. The effects of geometrical parameters of the proposed turbulator including the inner radius of the turbulator and the radius of the turbulator's holes are evaluated. Results indicate that the maximum effectiveness belongs to the case with inner diameter of the turbulator and radius of turbulator' holes equal to 19 and 3.6mm, respectively, at ṁ = 0.008 kg/s. Also, the generated swirl flows by the turbulator has a significant influence on heat transfer augmentation. Furthermore, a high inner radius of the turbulator leads to an increase in heat transfer rate and effectiveness, consequently. As a result, by increasing the inner radius of turbulator by 26.7%, the effectiveness rises by 80% (maximum at ṁ = 0.008 kg/s). Increasing the radius of turbulator's hole by 133.34% leadstoangrowthineffectivenessofabout50% (maximum at ṁ =0.058kg/s). [ABSTRACT FROM AUTHOR]

In this study, a numerical investigation for the fluid flow field analysis using different configuration dimple parameters in conjunction with an internal type insert in pipe is carried out. The effects of the dimple diameters with a center twisted tape on the flow pattern, pressure drop, friction factor, and heat transfer characteristics are investigated. The influence of the latter device on heat performance and thermal-hydraulic performance evaluation factor (PEF) were carried out in a pipe for fully developed flow with range for fully developed flow with range of Reynolds number (Re) of 1573 and 23 592. Experiments with numerical models are performed using different dimpled dimeters by inserting twisted tapes. The outcomes observe that the qualitative analysis for flow fields such as static pressure, dynamic pressure, velocity magnitude, wall shear stress, and turbulent kinetic energy as well as the quantities analysis for pressure drop, heat transfer coefficient friction factor, and Nu number in dimpled pipe fitted with twisted tape are greater than plain pipe. This is because using these devices cause more secondary flow, swirl flow, and flow mixing that lead to higher turbulence, which, in turn, enhance the overall heat transfer. The results indicated that the lower and higher values of thermal PEF are about 0.78 and 1.6, respectively, at the dimple dimmers of 1mm. [ABSTRACT FROM AUTHOR]