There are several factors that can cause the excessive accumulation of biofluid in human tissue, such as pregnancy, local traumas, allergic responses or the use of certain therapeutic medications. This study aims to further investigate the shear-dependent peristaltic flow of Phan–Thien–Tanner (PTT) fluid within a planar channel by incorporating the phenomenon of electro-osmosis. This research is driven by the potential biomedical applications of this knowledge. The non-Newtonian fluid features of the PTT fluid model are considered as physiological fluid in a symmetric planar channel. This study is significant, as it demonstrates that the chyme in the small intestine can be modelled as a PTT fluid. The governing equations for the flow of the ionic liquid, thermal radiation and heat transfer, along with the Poisson–Boltzmann equation within the electrical double layer, are discussed. The long-wavelength ($\delta \ll 1$) and low-Reynolds-number approximations ($Re \to 0$) are used to simplify the simultaneous equations. The solutions analyse the Debye electronic length parameter, Helmholtz–Smoluchowski velocity, Prandtl number and thermal radiation. Additionally, streamlines are used to examine the phenomenon of entrapment. Graphs are used to explain the influence of different parameters on the flow and temperature. The findings of the current model have practical implications in the design of microfluidic devices for different particle transport phenomena at the micro level. Additionally, the noteworthy results highlight the advantages of electro-osmosis in controlling both flow and heat transfer. Ultimately, our objective is to use these findings as a guide for the advancement of lab-on-a-chip systems.

In this research, the thermal transport behavior of the branched carbon nanotube (CNT) with T-junction was investigated using non-equilibrium molecular dynamics simulation. Both symmetric and asymmetric temperature-controlled simulations were imposed to evaluate how the heat flowed inside the branched CNT with three branches of equal length and same chirality. The branch length and strain effects on the heat flow were examined. In addition, the simulated heat flow was compared with the prediction made by conventional thermal circuit calculation based on diffusive phonon transport. The heat was observed to flow straight rather than sideway inside the branched CNT with T-junction under the asymmetric temperature setup; this finding contradicts the conventional thermal circuit calculation. There are two possible explanations for this phenomenon. One is ballistic phonon transport and the other is phonons have different interactions or scattering with the defective atomic configurations at the T-junction. Moreover, the tensile strain could tune the heat flow, a finding that might be useful in thermal management applications.

We perform direct numerical simulations of wall sheared Rayleigh–Bénard convection for Rayleigh numbers up to $Ra=10^{8}$, Prandtl number unity and wall shear Reynolds numbers up to $Re_{w}=10\,000$. Using the Monin–Obukhov length $L_{MO}$ we observe the presence of three different flow states, a buoyancy dominated regime ($L_{MO}\lesssim \unicode[STIX]{x1D706}_{\unicode[STIX]{x1D703}}$; with $\unicode[STIX]{x1D706}_{\unicode[STIX]{x1D703}}$ the thermal boundary layer thickness), a transitional regime ($0.5H\gtrsim L_{MO}\gtrsim \unicode[STIX]{x1D706}_{\unicode[STIX]{x1D703}}$; with $H$ the height of the domain) and a shear dominated regime ($L_{MO}\gtrsim 0.5H$). In the buoyancy dominated regime, the flow dynamics is similar to that of turbulent thermal convection. The transitional regime is characterized by rolls that are increasingly elongated with increasing shear. The flow in the shear dominated regime consists of very large-scale meandering rolls, similar to the ones found in conventional Couette flow. As a consequence of these different flow regimes, for fixed $Ra$ and with increasing shear, the heat transfer first decreases, due to the breakup of the thermal rolls, and then increases at the beginning of the shear dominated regime. In the shear dominated regime the Nusselt number $Nu$ effectively scales as $Nu\sim Ra^{\unicode[STIX]{x1D6FC}}$ with $\unicode[STIX]{x1D6FC}\ll 1/3$, while we find $\unicode[STIX]{x1D6FC}\simeq 0.30$ in the buoyancy dominated regime. In the transitional regime, the effective scaling exponent is $\unicode[STIX]{x1D6FC}>1/3$, but the temperature and velocity profiles in this regime are not logarithmic yet, thus indicating transient dynamics and not the ultimate regime of thermal convection.

Air-breathing propulsion has the potential to decrease the cost per kilogram for access-to-space, while increasing the flexibility of available low earth orbits. However, to meet the performance requirements, fuel-air mixing inside of scramjet engines and thermal management still need to be improved.

An option to address these issues is to use intrinsically generated vortices from scramjet inlets to enhance fuel-air mixing further downstream, leading to shorter, less internal drag generating, and thus more efficient engines. Previous works have studied this vortex-injection interaction numerically, but validation was impractical due to lack of published experimental data. This paper extends upon these previous works by providing experimental data for a canonical geometry, obtained in the T4 Stalker Tube at Mach 8 flight conditions, and assesses the accuracy of numerical methodologies such as RANS CFD to predict the vortex-injection interaction.

Focus is placed on understanding the ability of the numerical methodology to replicate the most important aspects of the vortex-injection interaction. Results show overall good agreement between the numerical and experimental results, as all major features are captured. However, limitations are encountered, especially due to a localised region of over predicted heat flux.

This study presents the heat transfer analysis of 90° elbow microchannel flow with sharp and curved turn designs. Experimental technique of temperature-sensitive paint was adapted in the experiment for measuring both fluid and surface temperature. The detailed information of fluid and surface temperature data were successfully acquired with a microscope system at Reynolds number varying from 50.5 to 101.1. Micro heaters were fabricated and positioned underneath the microchannel to provide the constant heat flux boundary condition. The utilization of micro heaters can prevent the axial heat conduction. The Nusselt number contours were obtained in this study with sharp and curved corners, which can provide detailed information of localized region with high and low heat transfer. The experimental approach performed in this study could be applied in the future for micro heat exchanger or heat sink design with complex microchannel systems.

Gas turbine blades feature multi-pass internal cooling channels, through which relatively colder air bled from the compressor is routed to cool internal walls. Under rotation, due to the influence of Coriolis force and centrifugal buoyancy, heat transfer at the trailing side enhances and that at the leading side reduces, for a radially outward flow. This non-uniform temperature distribution results in increased thermal stress, which is detrimental to blade life. In this study, a rotation configuration is presented which can negate the Coriolis force effect on heat and fluid flow, thereby maintaining uniform heat transfer on leading and trailing walls. A straight, smooth duct of unit aspect ratio is considered to demonstrate the concept and understand the fluid flow within the channel and its interaction with the walls. The new design is compared against the conventional rotation design. Numerical simulations under steady-state condition were carried out at a Reynolds number of 25000, where the Rotation numbers were varied as 0, 0.1, 0.15, 0.2, 0.25. Realisable version of k-$\varepsilon$ model was used for turbulence modelling. It was observed that new rotation (parallel) configuration’s heat transfer on leading and trailing sides were near similar, and trailing side was marginally higher compared to leading side. An interesting phenomenon of secondary Coriolis effect is reported which accounts for the minor differences in heat transfer augmentation between leading and trailing walls. Due to centrifugal buoyancy, the fluid is pushed towards the radially outward wall, resulting in a counter-rotating vortex pair, which also enhances the heat transfer on leading and trailing walls when compared to stationary case.

An experimental technique for assessing film cooling performance is proposed which can determine both film effectiveness and heat transfer coefficient distributions from a single infrared experiment. First, the film effectiveness is determined in the experiment’s steady-state phase on a series of film-cooled nozzle guide vane leading edge geometries made of a low thermal conductivity foam. Then, the effectiveness is used to calculate the distribution of the transient phase driving gas temperatures, which is applied to a finite element conduction model. Heat transfer coefficients are guessed and iteratively refined until the surface temperature histories predicted by the finite element model match those which were experimentally observed. Unlike conventional methods based on one-dimensional analytical heat transfer solutions, this approach does not require assumptions about the material thickness underlying the test surface or the uniformity with depth of its initial temperature distribution. This relieves certain experimental constraints and reduces uncertainty in results.

In an automated installation powered by direct current (DC), the boiling curves and heat-transfer-coefficient (HTC) dependencies on the superheat values (ΔT) under free convection conditions for the water nanodispersions of clay minerals – illite, montmorillonite, palygorskite and genetic mixtures of the latter two – were obtained. The effects of some factors on pool boiling heat transfer were also studied.

A significant influence of the shape and anisotropy of nanoparticles (NPs) on the heat-transfer parameters of nanofluids (NFs) was detected. A significant critical heat flux (CHF) enhancement (up to 200–300%) at boiling of the nanofluids studied was established, which is due to nanoparticle deposition on the heater surface during nanofluid boiling. The structure of the nanomaterials deposited is important in the enhancement of heat transfer at boiling of nanofluids and in avoiding boiling crises.

The present study showed the effectiveness of clay-mineral nanofluids for extra emergency cooling of overheated surfaces of powerful equipment in the event of the sudden onset of a boiling crisis.

When a gas turbine engine is shut down it will develop a circumferential thermal gradient vertically across the compressor due to hot air rising from the cooling metal components and pooling at the top. As the hot compressor rotor drum and casing cool and contract in the presence of this thermal gradient, they do so non-uniformly and therefore will bend slightly, in a phenomenon known as rotor bow. Starting an engine under bowed conditions can result in damage, representing a risk to both airworthiness and operational capability. This study consolidates some preliminary findings by the authors relating to the drivers for rotor bow, such as engine geometry, aircraft-engine integration and rotor temperature on shutdown. The commercial and military operational considerations associated with rotor bow are also discussed, including limitations which may result from a bowed rotor; the influence of operations including the final flight and descent profiles, taxi procedures and rapid turnaround requirements; as well as some practical solutions which may be implemented to reduce the impact of rotor bow.

A novel micromechanical approach is proposed to calculate the effective thermal conductivities of fiber reinforced composite materials. The key advantage of the present formulation is its ability to yield closed form solutions for the effective thermal conductivity of composites in both longitudinal and transverse directions for three dimensional heat transfer problems. The obtained results are in good agreement with the experimental data reported in the literature. When compared with analytical and finite element solutions, the results are seen to be in better agreement with the hexagonal packed array compared to the square packed array which thus represents a more realistic model of the fiber distribution in the matrix medium.

We have constrained the value for thermal diffusivity of near-surface snow and firn at Summit Station, Greenland, using a Fourier-type analysis applied to hourly temperature measurements collected from eight thermistors in a closed-off, air-filled borehole between May 2004 and July 2008. An implicit, finite-difference method suggests that a bulk diffusivity of ∼25 ± 3m2 a−1 is the most reasonable for representing macroscale heat transport in the top 30 m of firn and snow. This value represents an average diffusivity and, in a conduction-only model, generates temperature series whose phase shifts with depth most closely match those of the Summit borehole data (rms difference between measurements and model output is ∼6 days). This bulk value, derived numerically and corroborated analytically, is useful over large tracts of the Greenland ice sheet where density and microstructure are unknown.

In present work, we investigate numerical simulation of steady natural convection flow in the presence of weak magnetic Prandtl number and strong magnetic field by involving algebraic decay in mainstream velocity. Before passing to the numerical simulation, we formulate the set of boundary layer equations with the inclusion of the effects of algebraic decay velocity, aligned magnetic field and buoyant body force in the momentum equation. Later, finite difference method with primitive variable formulation is employed in the physical domain to compute the numerical solutions of the flow field. Graphical results for the velocity, temperature and transverse component of magnetic field as well as surface friction, rate of heat transfer and current density are presented and discussed. It is pertinent to mention that the simulation is performed for different values of algebraic decay parameter α, Prandtl number Pr, magnetic Prandtl number Pm and magnetic force parameter S.

Effects of viscous dissipation and radiation on MHD natural convection in oblique porous cavity with constant heat flux is studied numerically in the present article. The right inclined wall is maintained at a constant cold temperature Tc and the left inclined wall has a constant heat flux q with length S, while the remainder of the left wall is adiabatic. The horizontal walls are assumed to be adiabatic. The governing equations are obtained by applying the Darcy model and Boussinesq approximations. COMSOL's finite element method is used to solve the non-dimensional governing equations together with specified boundary conditions. The governing parameters of this study are Rayleigh number (Ra=10,100,200,250,500 and 1000), Hartmann number (0≤ Ha ≤20), inclination angle of the magnetic field (0° ≤ ω ≤ π/2), Radiation (0≤R≤15), the heater flux length (0.1≤H≤1) and inclination angle of the sloping wall (–π/3≤ϕ≤π/3). The results are considered for various values of the governing parameters in terms of streamlines, isotherms and averageNusselt number. It is found that the intensity of the streamlines and the isotherm patterns decrease with an increment in Hartmann number. The overall heat transfer is significantly increased with the increment of the viscous dissipation and the radiation parameters.