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The purpose of this paper is to numerically investigate the heat transfer performance of aviation kerosene flowing in smooth and enhanced tubes with asymmetric fins at supercritical pressures and to reveal the effects of several key parameters, such as mass flow rate, heat flux, pressure and inlet temperature on the heat transfer.

A CFD approach is taken and the strong variations of the thermo-physical properties as the critical point is passed are taken into account. The RNG k-ε model is applied for simulating turbulent flow conditions.

The numerical results reveal that the heat transfer coefficient increases with increasing mass flow rate and inlet temperature. The effect of heat flux on heat transfer is more complicated, while the effect of pressure on heat transfer is insignificant. The considered asymmetric fins have a small effect on the fluid temperature, but the wall temperature is reduced significantly by the asymmetric fins compared to that of the corresponding smooth tube. As a result, the asymmetric finned tube leads to a significant heat transfer enhancement (an increase in the heat transfer coefficient about 23-41 percent). The enhancement might be caused by the re-development of velocity and temperature boundary layers in the enhanced tubes. With the asymmetric fins, the pressure loss in the enhanced tubes is slightly larger than that in the smooth tube. A thermal performance factor is applied for combined evaluation of heat transfer enhancement and pressure loss.

The asymmetric fins also caused an increased pressure loss. A thermal performance factor ? was used for combined evaluation of heat transfer enhancement and pressure loss. Results show that the two enhanced tubes perform better than the smooth tube. The enhanced tube 2 gave better overall heat transfer performance than the enhanced tube 1. It is suggested that the geometric parameters of the asymmetric fins should be optimized to further improve the thermal performance and also various structures need to be investigated.

The asymmetric fins increased the pressure loss. The evaluation of heat transfer enhancement and pressure loss Results showed that the two enhanced tubes perform better than the smooth tube. It is suggested that the geometric parameters of the asymmetric fins should be optimized to further improve the thermal performance and also various structures need to be investigated to make the results more engineering useful.

The paper presents unique solutions for thermal performance of a fluid at near critical state in smooth and enhanced tubes. The findings are of relevance for design and thermal optimization particularly in aerospace applications.

This paper aims to focus on flow boiling heat transfer in an asymmetrically heated minichannel. Two-dimensional inverse heat transfer problem was solved using the Trefftz and Beck methods. The primary purpose was to find an enhanced surface that could help intensify heat transfer.

The experimental set-up and methodology for FC-72 boiling heat transfer in two parallel vertical rectangular minichannels with smooth or enhanced heated surfaces was presented. The heat transfer coefficient was calculated using the Trefftz and Beck methods.

The results confirm that considerable heat transfer enhancement takes place when selected enhanced heated surface is used in the minichannel flow boiling and that it depends on the type of surface enhancement. The analysis of the experimental data revealed that the values and distributions of the heat transfer coefficient obtained using the Beck and Trefftz methods were similar.

Many studies have been recently devoted to flow boiling heat transfer in minichannels because of the rapid development of high-performance integrated systems generating large amounts of heat. Highly efficient small-size cooling systems for new-generation compact devices are thus in great demand.

The present results are original and new in the study of cooling liquid boiling in minichannels with enhanced heated surfaces that contribute to heat transfer enhancement. The paper allows the verification of state-of-the-art methods of solving the inverse problem by using empirical data from the experiment. The application of the Trefftz and Beck methods for finding a solution of the inverse heat transfer problem is promising.

The purpose of this paper is to enhance the heat transfer and thermal performance in the trailing edge region of the vane with vortex generators (VGs).

This numerical study presents the enhancement of thermal performance in the trailing part of a gas turbine blade. In the trailing part, generally, pin fins are used either in staggered or in-line arrangements to enhance the heat transfer. In this study, based on the idea from heat exchangers, pin fins are combined with VGs. A pair of VGs is embedded in the boundary layer upstream of each pin fin in the first row of the pin fin array having an in-line configuration. The effects of the VG angle relative to the streamwise direction and streamwise distance between the pin fin and VGs are investigated at various Reynolds numbers.

The results indicated that the endwall heat transfer is enhanced with the addition of VGs and the heat transfer from the surfaces of the pin fins. The level of heat transfer enhancement compared to the case without VGs is more significant at high Reynolds number. The surfaces of the VGs also show a significant amount of heat transfer. Study of the angle of the attack suggested that a high angle of attack is more appropriate for pin fin cooling enhancement whereas an intermediate gap between the VGs and pin fins shows considerable improvement of thermal performance compared to the small and large gaps. The phenomenon of heat transfer augmentation with the VGs is demonstrated by the flow field. It shows that the enhancement of heat transfer is governed by the mixing of the flow as a result of the interaction of vortices generated by the VGs and pin fins.

VGs are used to disturb the thermal boundary layer. It shows that heat transfer is augmented as a result of the interaction of vortices associated with VGs and pin fins.

Nanofluid exhibits higher density, higher viscosity, higher thermal conductivity and reduced specific heat capacity along with improved heat transfer characteristics. It is comparatively better than conventional fluids in terms of thermo-physical properties. This paper aims to investigate experimentally the overall performance of the shell and tube heat exchanger operated under two different configurations – without baffles (STHX_1) and with baffles (STHX_2) using 0.01 Vol.% and 0.02 Vol.% of CuO-W nanofluid.

Two different configurations, one without baffles (STHX_1) and other with single segmental baffles (STHX_2), are chosen with all other dimensional details of shell and tube remaining same. Water is used as base fluid. CuO nanoparticle is chosen, as its thermal conductivity is higher compared to other metal oxides. A comparative study on the thermal performance of these shell and tube heat exchangers are performed by considering different Vol.% concentrations of CuO-W nanofluid and the outcome are compared with the base fluid (i.e., water). The influence of varying the mass flow rate of the tube side fluid by keeping shell side fluid mass flow rate as constant and vice versa on the thermal performance of shell and tube heat exchanger are studied.

The modified shell and tube heat exchanger with baffles (STHX_2) give an improved performance. The heat transfer coefficient improved by about 11.28 and 7.54 per cent for 0.02 and 0.01 Vol.% of CuO-W nanofluid compared to water. Overall heat transfer coefficient for STHX_2 enhanced between 118.26% to 123.06% in comparison with base fluid for 0.02 Vol.% of CuO-W nanofluid whereas, it improved between 79.20% to 87.51% for 0.01 Vol.% of CuO-W nanofluid. Similarly, the actual heat transfer enhanced between 71.79% to 77.77% and between 48.71% to 55.55% for 0.02 and 0.01 Vol.% of CuO-W nanofluid, respectively. Moreover, mass flow rates of the working fluids significantly influence the performance of the shell and tube heat exchanger.

Two cases are considered here. first, by varying the shell side fluid mass flow rate and keeping the tube side fluid mass flow rate as constant. Later, tube side fluid mass flow rates are varied and shell side fluid mass flow rate is kept constant. It is found that in Case 2, for both 0.01 and 0.02 Vol.% of CuO-W nanofluid, highest performance is obtained for 150 kg/h of shell side and tube side fluid flows involving STHX_2. Finally, the modified shell and tube heat exchanger with baffle arrangement gives the best performance by using 0.02 Vol.% of CuO-W nanofluid.

This study aims to computational numerical simulations to clarify and explore the influences of periodic cellular lattice (PCL) morphological parameters – such as lattice structure topology (simple cubic, body-centered cubic, z-reinforced body-centered cubic [BCCZ], face-centered cubic and z-reinforced face-centered cubic [FCCZ] lattice structures) and porosity value ( ) – on the thermal-hydraulic characteristics of the novel trussed fin-and-elliptical tube heat exchanger (FETHX), which has led to a deeper understanding of the superior heat transfer enhancement ability of the PCL structure.

A three-dimensional computational fluid dynamics (CFD) model is proposed in this paper to provide better understanding of the fluid flow and heat transfer behavior of the PCL structures in the trussed FETHXs associated with different structure topologies and high-porosities. The flow governing equations of the trussed FETHX are solved by the CFD software ANSYS CFX® and use the Menter SST turbulence model to accurately predict flow characteristics in the fluid flow region.

The thermal-hydraulic performance benchmarks analysis – such as field synergy performance and performance evaluation criteria – conducted during this research successfully identified demonstrates that if the high porosity of all PCL structures decrease to 92%, the best thermal-hydraulic performance is provided. Overall, according to the obtained outcomes, the trussed FETHX with the advantages of using BCCZ lattice structure at 92% porosity presents good thermal-hydraulic performance enhancement among all the investigated PCL structures.

To the best of the authors’ knowledge, this paper is one of the first in the literature that provides thorough thermal-hydraulic characteristics of a novel trussed FETHX with high-porosity PCL structures.

This study comprehensively examines entropy generation and thermosolutal performance of a ternary hybrid nanofluid in a partially active porous cabinet. The purpose of this study is to comprehend the intricate phenomena of double diffusion by investigating the dispersion behavior of Al₂O₃, CuO, and Ag nanoparticles in water.

The cabinet design consists of two horizontal walls and two curved walls with the lower border divided into a heated and concentrated region of length b and the remaining sections are adiabatic. The vertical borders are cold and low concentration, while the upper border is adiabatic. Two cavity configurations such as convex and concave are considered. A uniform porous medium is taken within the ternary hybrid nanofluid. This has been characterized by the Brinkman-extended Darcy model. Thermosolutal phenomena are governed by the Navier-Stokes equations and are solved by adopting a higher-order compact scheme.

The present study focuses on exploring the influence of several well-defined parameters, including Rayleigh number, Darcy number, Lewis number, Buoyancy ratio number, nanoparticle volume concentration and heater size. The results indicate that the ternary hybrid nanofluid outperforms both the mono and hybrid nanofluids in all considered aspects.

This study brings forth a significant contribution by uncovering novel flow features that have previously remained unexplored. By addressing a well-defined problem, the work provides valuable insights into the enhancement of thermal transport, with direct implications for diverse engineering devices such as solar collectors, heat exchangers and microelectronics.

Re<95,000 based on hydraulic diameter, heat transfer and turbulent flow through a rectangular‐sectioned 90° bend was investigated numerically and experimentally. To develop turbulence level, square prism and cylindrical obstacles was placed in the center of the bend.

For heat transfer, uniform heat flux of 5,000 W/m² from bend surfaces is assumed. Numerical analysis was realized for both the turbulent flow and heat transfer. For numerical study, FLUENT 6.1.22 code, RSM turbulence model, hybrid hexahedral‐tetrahedral cell structures and uniform inlet velocity assumption were selected. For the pressure distribution in the bend and velocity profile at the outlet of the bend, the experiments was carried out by means of manometers with ethyl alcohol, Mano‐air 500 Equipment and pitot‐static tube.

There was a high level of validation obtained between the numerical and the experimental results. Thereby, the mentioned numerical calculation method can be used most engineering applications. For Re>20,000, the square prism obstacles provide higher turbulence level and more favorable heat transfer than cylindrical obstacles. For Re<20,000, the obstacle use would not require for enhanced heat transfer aim. The obstacle in the bend cause considerably pressure drop in the bend.

The turbulent flow in the bend without obstacle has been numerically investigated by various turbulence models with the non‐refined mesh structure and various wall functions. For numerical solution of the turbulence flows and the heat transfer in the rectangular bend with obstacles, the FLUENT code and RSM turbulence model with enhanced wall functions are selected. In order to adapt the cell size and number to the turbulent flow the mesh structure was refined over curvature of turbulence dissipation rate in the bend.

The purpose of this study is to analyze the heat transfer and flow enhancement of an Al₂O₃-water nanofluid filling an inclined channel whose lower wall is embedded with periodically placed discrete hydrophobic heat sources. Formation of a thin depletion layer of low viscosity over each hydrophobic heated patch leads to the velocity slip and temperature jump condition at the interface of the hydrophobic patch.

The mixed convection of the nanofluid is analysed based on the two-phase non-homogeneous model. The governing equations are solved numerically through a control volume approach. A periodic boundary condition is adopted along the longitudinal direction of the modulated channel. A velocity slip and temperature jump condition are imposed along with the hydrophobic heated stripes. The paper has validated the present non-homogeneous model with existing experimental and numerical results for particular cases. The impact of temperature jump condition and slip velocity on the flow and thermal field of the nanofluid in mixed convection is analysed for a wide range of governing parameters, namely, Reynolds number (50 ≤ Re ≤ 150), Grashof number ( 103≤Gr≤5×104), nanoparticle bulk volume fraction ( 0.01≤φb≤0.05), nanoparticle diameter ( 30≤dp≤60) and the angle of inclination ( −60°≤σ≤60°).

The presence of the thin depletion layer above the heated stripes reduces the heat transfer and augments the volume flow rate. Consideration of the nanofluid as a coolant enhances the rate of heat transfer, as well as the entropy generation and friction factor compared to the clear fluid. However, the rate of increment in heat transfer suppresses by a significant margin of the loss due to enhanced entropy generation and friction factor. Heat transfer performance of the channel diminishes as the channel inclination angle with the horizontal is increased. The paper has also compared the non-homogeneous model with the corresponding homogeneous model. In the non-homogeneous formulation, the nanoparticle distribution is directly affected by the slip conditions by virtue of the no-normal flux of nanoparticles on the slip planes. For this, the slip stripes augment the impact of nanoparticle volume fraction compared to the no-slip case.

This paper finds that the periodically arranged hydrophobic heat sources on the lower wall of the channel create a significant augmentation in the volume flow rate, which may be crucial to augment the transport process in mini- or micro-channels. This type of configuration has not been addressed in the existing literature.

We present a new nonlinear axisymmetric finite element model for heat transfer and powder deposition in rotational molding. Arbitrary Lagrangian Eulerian techniques are employed to track the gradual growth of the plastic layer. Results using this approach compare well with earlier 1‐D models and with experimental data. Using the model to study the effects of locally enhanced heat transfer on part wall thickness, we find that controlling the relative magnitudes of radial and circumferential heat transfer is crucial in order to obtain desired wall thickness profiles.

The purpose of the study is to propose a novel implementation of twisted tape in sinusoidal wavy-walled tubes to enhance the rate of heat transfer without compromising thermal efficiency. The study numerically investigates the fluid flow characteristics and analyzes the effect of different geometrical configurations, including wall wave amplitude, tape twist angles and nanoparticle volume fractions, on heat transfer improvement and performance factor.

This problem is numerically investigated using computational fluid dynamics, and the method is the finite volume method. A two-phase mixture model is used for nanofluid modeling.

The study investigated the effect of wall waviness, twisted tape, and nanoparticles on forced convective heat transfer and friction factor behavior in laminar pipe flow in three different Reynolds number regimes. The results showed that implementing twisted tape in wavy tubes significantly increased the rate of heat transfer and the performance factor, with the best twist ratio between 90 and 180°. Adding nanoparticles also enhanced heat transfer and performance factor, but to a lesser extent than wavy wall-twisted tape combinations. The study suggests selecting a proper combination of wavy wall and twisted tape at each Reynolds number to achieve an optimum solution.

To the best of the authors’ knowledge, the implementation of the selected passive methods in sinusoidal wavy tubes has not been studied before, and no previous studies have taken into account such a mix of heat transfer improvement techniques.