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With the growing number of high-rise buildings and the increasing incidence of electrical fires, copper wire overcurrent has become a major factor causing disasters. Hence, it is imperative to investigate the heating law of copper wire overcurrent. To address the unclear overcurrent heating characteristics of copper wires at different inclination angles, an angle adjustment device (0°–90°) was designed to build an experimental system for simulating electrical fire faults. Using a FAST-M200 high-speed infrared thermal imager, the temperature information during heating of PVC copper wires (cross-sectional area: 2.5 mm2) was collected at various inclination angles, aiming to explore the temperature evolution law over the overcurrent heating process of the wires at various inclination angles, and analyze the effects of inclination angle on the stage stagnation time and fire current ignition time of the wires. The results show that under the overcurrent condition, the temperatures of copper wires with different inclination angles present a phased growth trend. When the inclination angle is fixed, the temperature feature points of copper wires appear in advance at different heating stages. After the insulating layer temperature reaches the pyrolysis limit, the inclination angle generates little effect on the copper wire stagnation time at each stage when the current is higher than 192 A. At an inclination angle range of 0°–75°, the wire ignition time decreases with the increasing inclination angle. Moreover, the findings provide a basis for the deductive inference of electrical fire occurrence and development as well as the investigation and identification of fire accidents. [ABSTRACT FROM AUTHOR]

This study investigates experimentally the fuel bed width effect on concurrent flame spread over discrete fuels. Two representative configurations, dense arrays spaced 3 mm and loose arrays spaced 6 mm, are concerned herein. Regular birch rod arrays were designed by varying five kinds of column numbers (denoted by n, 3, 5, 7, 9, and 11) and five slopes (θ, 0, 15°, 30°, 45°, and 60°). Results show that flame spread rate (FSR) of dense arrays is lower than that of loose arrays. A predicted model of FSR is also developed, which is in good agreement with experimental results. Moreover, compared with the loose arrays, the decay of heat flux in the thermal plume region behind the pyrolysis zone is more rapid for dense arrays. For dense arrays, with increasing inclination angle, maximum convective heat flux, mass loss rate, and flame length decrease first and then increase at n > 5, but have an increasing tendency for loose arrays. Furthermore, the fuel consumption efficiency of loose arrays has an obvious superiority over dense arrays when θ > 15˚. In addition, dimensionless correlations between flame length and heat release rate are proposed both for dense and loose arrays. [ABSTRACT FROM AUTHOR]

A numerical analysis was carried out of mixed convection heat transfer for a laminar flow in a rectangular inclined microchannel totally filled with a water/Al2O3 nanofluid. The governing conservation equations are translated into a dimensionless form using the thermal single relaxation time and they modify the lattice Boltzmann method with double distribution functions. The viscous dissipation effects are adapted to the energy equation. The effects of nanoparticle volume fractions ϕ (0 ≤ ϕ ≤ 0.04) and inclination angles γ (0° ≤ γ ≤ 60°) on the flow of the nanofluid and the heat transfer are investigated. The obtained results are presented in terms of streamlines, isotherms, slip velocity, wall temperature and Nusselt number. The results show that the higher values of the volume fraction of Al2O3 and the large values of inclination angles improve the heat transfer rate. [ABSTRACT FROM AUTHOR]

A two-phase closed thermosyphon (TPCT) with a CuO–H2O nanofluid was used to effectively harness the internal accumulation of thermal energy from a coal pile, formerly subject to the risk of spontaneous combustion. The heat transfer effect of different insertion ratios of the TPCT (evaporation section:condensation section = 1:3, 1:2, and 2:3) and inclination angles (30°, 45°, 60°, and 90°) was investigated for bituminous coal. The results indicated that the heat transfer effect of the insertion ratio, in descending order of preference, was 2:3 > 1:2 > 1:3. When the TPCT insertion ratio was 2:3, the maximum temperature difference was up to 37.7 °C. The heat transfer effects of the TPCT were strengthened when it was inserted at a given angle. In decreasing order of effectiveness, the tested inclination angles showed the following order of preference: 60° > 30° > 45° > 90°. Therefore, 60° was the optimal insertion angle. In general, TPCT has the optimal transfer effects when the insertion ratio is 2:3 and the inclination angle is 60°. [ABSTRACT FROM AUTHOR]

In the present framework, the combined effect of magnetic field (Hartmann number, Ha), angle of inclination (α) , nanoparticle volume fraction (χ) , number of oscillations (N) and aspect ratio (AR) is investigated for natural convective heat transfer analysis containing hybrid nanofluid suspension ( Al 2 O 3 and Cu) in wavy annulus having circular heater in the center and discrete coolers on the wavy walls. The homogeneous hybrid nanoliquid (0.1% of Al 2 O 3 - Cu / water ) model with fitted correlations of viscosity and thermal conductivity from the experimental data is used, and results are evaluated for different ranges of controlling parameters: Rayleigh numbers ( Ra = 10 3 – 10 6 ), Hartmann number (Ha = 0–50), aspect ratio (AR (D/H) = 0.2–0.6), number of oscillations or undulation parameter ( N = 2 –8) with fixed amplitude ( a = 0.02 ), angle of inclination ( α = 0 ∘ – 135 ∘ ) and nanoparticle volume fraction ( χ = 0 –0.02) using Galerkin finite element method (GFEM) with triangular mesh. The mesh grid independency test has been conducted with different meshes (degree of freedoms), and a refined mesh with domain elements = 21,662, boundary elements = 884 and degree of freedoms (DOFs) = 179,703 has been selected for entire computations. The average Nusselt number is evaluated as a function of Ra, α and N for different parametric ranges of χ , Ha and AR, respectively. The average heat transfer follows as zigzag pattern with increment in waviness (undulation parameter), and it has a minimum value for inclination angle = π / 2 . With high Rayleigh number ( Ra > 10 5 ), the average Nusselt number shows opposite trend with hybrid nanoparticle concentration. This type of research can be used in the design of an appropriate nanofluid-based cooling system for electronic components to ensure effective operational conditions. [ABSTRACT FROM AUTHOR]

Understanding the fire characteristics of stayed-cable bridge, such as fire growth, during accidental fire is essential to develop prevention strategies for potential damage. This study focuses on the effects of high cable fire that may result from a short circuit or a lightning strike since high flammability heat release characteristics of HDPE sheath causes burning of nearby cables. Fire propagation behaviors on one single cable and between two adjacent cables under working conditions with different inclination angles were obtained. The temperature distribution, drop ignition behaviors and flame spread rate were analyzed. The results show that flame propagation characteristics of stay cables seriously changed as the angle of inclination increases, which explain the fracture sequence of cables to some extent for the Red Stone Bridge fire event. The particle size of molten substance formed by combustion of the upper-layer cables increases, and the ignition position for the under-layer cable gradually moves down as the increase of inclination angle. Moreover, increased inclination angle also resulted in increase in flame height and molten drops flow rate and reduce in the duration of the prosperity stage for cable fire. Although HDPE sheath is a protective device, it does prevent the combustion for inner strands from becoming intense, but once ignited, would become the main fire load, promoting fire development. [ABSTRACT FROM AUTHOR]

Natural convection heat transfer of SiO2/water nanofluids in a rectangular enclosure was investigated at different concentrations and inclination angles, experimentally. Results indicated that heat transfer has not significantly changed for low concentrations of nanofluids. However, at volume fraction of nanoparticles greater than 0.005, heat transfer coefficient decreased with concentration of nanofluid. The effect of tilt angle on heat transfer was also examined. It was found that at low concentrations of nanofluid, the effect of tilt angle on Nusselt number is more pronounced. Influence of concentration of nanofluid on Nusselt number decreases with increasing inclination angle of the cavity or approaching the heated wall to vertical state. The highest values of Nusselt number were obtained for tilt angles of 0° or horizontal state, and heat transfer rate was decreased with inclination angle. [ABSTRACT FROM AUTHOR]

As a new type of condensation-heat-transfer facility, nano-porous ceramic membrane tube is surrounded by nano-porous wall surface, which is hydrophilic to capture the vapor or condensate. In general, water vapor will condense into liquid near the wall surface or inside its nano-sized pores, wherein its latent heat will be released synchronously. Thus, an amount of heat and water can be recovered by using nano-porous ceramic membrane tube. Experiments are performed using a 10-nm ceramic membrane tube and a traditional condensation-heat-transfer tube (a 304 stainless steel tube in the experiment) with the same dimensions. The gas mixture consisting of nitrogen (N2) and water vapor is employed as working fluid, and the low-temperature water is used as the cold source. Great attention is paid to contrastively evaluate the heat-transfer and water-recovery performance of two kinds of tubes at different influential parameters (e.g., inclination angle). Compared with stainless steel tube, ceramic membrane tube has a more outstanding heat-transfer characteristic; it can enhance the cooling water temperature by 125% maximally. In addition, condensation-heat-transfer process of 10-nm ceramic membrane tube is influenced by inclination angle more significantly. In the 10-nm ceramic membrane tube, it has highest condensation-heat-transfer coefficient at horizontal flow (θ = 0°) and lowest at vertical down flow (θ = − 90°). Finally, water-recovery mass flux in the 10-nm ceramic membrane tube is higher than that in stainless steel tube, especially for the transmembrane pressure difference is higher than 3.83 kPa. This paper is useful for ceramic membrane condenser arrangement and design. [ABSTRACT FROM AUTHOR]

In this work, a detailed numerical investigation has been carried out to study the forced convection heat transfer from an inclined elliptic cylinder of a fixed aspect ratio of 0.5 immersed in a streaming water-based Al2O3 nanofluid using the two-phase Buongiorno's model. In particular, this study presents extensive numerical results on how the cylinder inclination angle, nanoparticle volume fraction and its size are going to influence the local flow, temperature and nanoparticle concentration fields in the vicinity of the cylinder surface as well as the gross engineering parameters like the drag coefficient and Nusselt number over the following ranges of conditions as: Reynolds number, 0.01 ≤ R e ≤ 40 ; cylinder inclination angle, 0 ≤ λ ≤ 90 ; nanoparticle volume fraction, 0 ≤ ϕ ≤ 0.06 and two nanoparticle sizes (dnp), namely 30 nm and 60 nm. It has been found that both the Nusselt number and drag force increase with ϕ , but decrease with dnp under otherwise identical conditions. On the other hand, at a particular value of Re, ϕ and dnp, the value of the average Nusselt number increases with the increasing values of λ , whereas the value of the drag coefficient decreases. Finally, from an application standpoint, a simple analytical formula for the average Nusselt number is provided as a function of Re, ϕ and λ which will facilitate the interpolation of the present results for the intermediate values of these governing parameters. [ABSTRACT FROM AUTHOR]

Mixed convection flow of aluminium-oxide nanoparticles in water through a circular tube was modelled using the discrete phase model and implemented on ANSYS-Fluent 17.0 through customised user-defined functions. The inclination angle was varied to study its effect on the migration and deposition of the nanoparticles. Experimentally determined thermo-physical properties were used in the analysis instead of theoretical or empirical models from the literature. Varying inclination angles were found to significantly affect the migration and deposition of nanoparticles. A critical angle of maximum deposition of approximately 30° was found for volume concentrations 1%, 3% and 5%. The effect of varying inclination angle on the heat transfer coefficient was minimal for low angles of inclination between 0 and 35% and decreased significantly after 40%. The effect of Saffman's lift, thermophoretic, Magnus and Brownian effects were also investigated, and results show that thermophoretic and Brownian effects were most dominant effects. [ABSTRACT FROM AUTHOR]

In this study, the characteristics of mixed convection heat transfer of nanofluids in circular microchannels with 500 μm diameter were investigated experimentally. In the study, water and water-based SiO2 nanofluids were used as the working fluid, and volumetric particle ratios of the nanofluids were selected as 0.2 and 0.4%. The thermal conductivity and viscosity characterizations of all fluids were performed in the temperature range of 20-60 °C, and the characteristics related to the temperature obtained from the measurements were used in calculations. The effect of the microchannel inclination angle and particle volumetric ratio on the mixed convection heat transfer characteristics was investigated. Upon examining the results, it was revealed that the range of 13-35% of the total heat transfer was generated by the natural convection effects. Increasing the inclination angle of the test section provided an enhancement between 4 and 13% in the total heat transfer. Furthermore, the increase in the volumetric particle ratio increased both forced convection heat transfer and the natural convection heat transfer components. Adding nanosized SiO2 particles into the water caused the total heat transfer to increase from 12 to 14% for 0.2 vol% and from 29 to 32% for 0.4 vol%. [ABSTRACT FROM AUTHOR]

The flow and thermal behavior of the phase change material in a novel geometry, namely, quadrantal cavity, is investigated numerically. The influences of curved wall temperatures of 32, 37, and 42 °C, the initial sub-cooling temperatures of 5, 10, and 15 °C which are lower than ambient temperature, are examined previously. Inclination angles for the range from 0 to 360° on flow and thermal performances are carefully studied. It is found that the inclination angles affects dramatically not only the time of complete thermal energy storage but also convection currents. The best performance is obtained for an inclination angle of 225°. [ABSTRACT FROM AUTHOR]