Low Heat Transfer Coefficient Research Articles

Thermo-hydraulic performance analysis of a solar air heater roughened with discrete reverse NACA profile ribs

The solar air heater has a relatively lower convection heat transfer coefficient because of development of a laminar sub-layer beneath the absorber plate. The heat transfer coefficient can be improved by interrupting the laminar sub-layer by providing artificial ribs on the flow facing side of the absorber plate. In the present study, a novel type of discrete reverse NACA 0040 profile ribs are used for the performance enhancement of the solar air heater. Various discrete rib parameters such as angle of groove (α, range: 15°–90°), relative gap between the grooves (g/l, range: 0.143–0.333) and relative width of the groove (w/e, range: 0.667–1.667) were optimized for the Reynolds number (Re) range of 6000–18000. Among the various discrete rib parameters, the optimum values were found to be α = 30°, g/l = 0.167 and w/e = 1.333. For this combination, the maximum thermo-hydraulic performance parameter based on the numerical and experimental analysis was found to be 2.65 and 2.578 respectively at the Reynolds number of 6000. The empirical correlations were developed to predict Nusselt number and the friction factor in terms of Re, α/90, g/l and w/e and observed to deviate within ±6% of the corresponding numerical values.

Experimental investigation for heat and flow characteristics of solar air heater having symmetrical gaps in multiple-arc rib pattern as roughness elements

ABSTRACT The working medium is air in a solar air heater (SAH) and because of its low heat-transfer coefficient, SAH results in poor performance. By placing artificial-roughness over the heat-collector plate, the performance of a SAH can be improved significantly. The improvement in thermal and hydraulic performance by providing multiple-arc-rib roughnesses patterns with the gap is discussed and generalized correlations are developed for Nusselt number and friction factor based on results collected from the experimentation (under steady condition). In total seven parameters were considered to study heat transfer and friction characteristics, that is, Reynolds number, rib-pitch, rib-height, number of gaps, arc-attack angle, rib, and gap width. In comparison to smooth collector-plate type of solar air heater, the 5.76 and 6.05 times higher Nusselt number and friction factor obtained in the proposed roughened SAH. Besides this, the developed mathematical expression for Nusselt number and friction factor shows close-fit with the experimental data under the error band of only 10 and 12%, respectively.

Improving appearance quality of injection molded microcellular parts through mold coating of PTFE and zirconia

AbstractThe application of microcellular parts in the field of high appearance quality is limited due to its appearance defects. In order to improve the appearance quality of microcellular parts, low heat transfer coefficient mold coating with PTFE and zirconia was employed in this study. The appearance quality of microcellular was evaluated by the surface roughness of microcellular parts. The numerical and experimental results show that delayed heat transfer between the melt and the mold can be achieved through both mold coatings, which improve the melt fluidity and reduce the shear force of the mold on the melt effectively. It is demonstrated that the PTFE has a better effect of delay heat transfer under thinner coating. The polished zirconia coating shows more conducive to the melt wall slip due to its stable molecular structure and smooth surface, resulting in microcellular parts with better appearance quality.

Investigation of heat transfer performance of alumina nanofluid flowing in the horizontal tube using fuzzy logic rules

ABSTRACT For the prediction of the heat transfer coefficient (HTC) of water-alumina nanofluid, the fuzzy theory was implemented in the current investigation. For the experimental setup validation, the HTC of water acquired from the experiments at varying pressure was validated with the HTC acquired from the correlation of Chen. Experiments were performed for water-alumina nanofluid at pressure (1–2 bar), mass flux (676–1,014 kg m−2 s−1), volumetric concentration (0.05–0.15%), and heat flux (94–143 kW m−2). Increment in the HTC of water-alumina nanofluid was noticed with the increment in the pressure, mass flux, concentration, and heat flux. Highest HTC of water-alumina nanofluid was 81.08 kW m−2 K−1 noticed at mass flux 1,014 kg m−2 s−1, concentration 0.15%, pressure 2 bar, and heat flux 143 kW m−2. The lowest HTC of water-alumina nanofluid was 21.94 kW m−2 K−1 noticed at mass flux 676 kg m−2 s−1, concentration 0.05%, pressure 1 bar, and heat flux 94 kW m−2. The interaction plots showed the influence of pressure, mass flux, concentration, and heat flux on the HTC of water-alumina nanofluid. The signal-to-noise ratio was employed to study the thermal performance characteristics for the flow boiling of water-alumina nanofluid. Ross, Roy, and Kumar formula was used for predicting the HTC of alumina nanofluid, and there was an error of 10.96% among the predicted and the experimental HTC. The fuzzy logic system showed a fine performance as the average error among the predicted and experimental HTC of water-alumina nanofluid was 0.29%.

Multi-objective optimization and analysis of performance of a four-temperature-level multi-irreversible absorption heat pump

Performance analysis and multi-objective optimization based on finite-time thermodynamics are conducted in this paper for an absorption heat pump operating between four temperature levels. The exergy-based ecological (E), the exergetic performance (EPC) and the thermo-economic (F) criteria were considered as the objective functions. The maxima of the three objective functions and the corresponding optimal conditions were obtained by applying the flowchart optimization methodology. The influences of some design factors such as the economic indicators, internal irreversibility parameters, heat-transfer coefficients of heat exchangers and the distribution ratio rate of the total heat-reject quantity between the absorber and the condenser on the maxima of the exergy-based ecological (E), the exergetic performance (EPC) and the thermo-economic (F) objective functions and the corresponding optimal parameters have been analyzed and discussed. The results show that: (i) Materials with a low heat-transfer coefficient significantly affect the performance of the system. (ii) The detrimental effects of internal irreversibilities depend on the order of magnitude of the optimal heat-transfer rates in the absorber and the condenser. Finally, (iii) the optimum performance has been obtained for certain values of the heat exchange surface area and the exergy input rate from an economic point of view.

Performansi Pipa Bersirip Alat Penukar Kalor Udara-Tanah Menggunakan Siklus Terbuka

In heat exchanger analysis using the Earth Air Heat Exchanger method, the overall heat transfer coefficient is known. This tool uses tubes in its design. The weakness of tube and plate type heat exchangers is the relatively low heat transfer coefficient, which can only reach a maximum of 60%. Therefore, a method to improve the heat transfer efficiency is using a fin. The purpose of this study is to calculate and compare the effectiveness (ε) value of experimental and theoretical of the Earth Air Heat Exchanger, as well as to find out the value of the coefficient of performance. The result showed that the average COP value of the experimental result is 0.63 at a speed of 1 m / s, 0.54 at the speed of 2 m / s, and 0.75 at the speed of 3 m / s, while theoretically is 0 , 73 at 1 m / s, 0.57 at 2 m / s, and 0.80 at 3m / s. For the value of the average effectiveness of the experimental results obtained 0.85 at the speed of 1 m / s, 0.93 at the speed of 2 m / s, and 0.89 at the speed of 3 m / s, while the theoretical result is 0.995 at the speed of 1 m / s, 0.997 at 2 m / s, and 0.998 at 3 m / s.

Compensating for the end-plate effect on heat transfer in brazed plate heat exchangers

• The end-plate effect in brazed plate heat exchangers is theoretically analyzed. • Numerical and analytical models are developed to quantify the end-plate effect. • The developed models are validated by the experiments. • An algorithm is developed to correct the end-plate effect in heat transfer tests. The two end plates in plate heat exchangers transfer heat through contact with the corrugated surface of the adjacent thermal plate. This phenomenon effectively increases the active heat transfer area and significantly affects the heat transfer when the heat exchanger has a very small number of plates. That is especially important when such a heat exchanger is used for the determination of the heat transfer coefficient in the development of heat transfer correlations. This paper presents a theoretical analysis of the effect of the end plate on heat transfer in brazed plate heat exchangers. The governing equations are derived through the energy balance analysis for a small element of the end plate. Numerical and analytical models are developed to solve the governing equations. The predictions by the two models agree well with each other. The heat transfer data for single-phase water in the BPHEs with different numbers of plates are used to validate the developed models. Both experiments and theoretical analyses show that the influence of the end plate is more significant in a heat exchanger with a small number of plates and a lower convective heat transfer coefficient. An iteration algorithm is developed to compensate for the end-plate effect in the development of heat transfer correlations.

Experimental Characterization of the Heat Transfer in Multi-Microchannel Heat Sinks for Two-Phase Cooling of Power Electronics

This study aims to characterize experimentally the heat transfer in micro-milled multi-microchannels copper heat sinks operating with flow boiling, in the attempt to contribute to the development of novel and high heat flux thermal management systems for power electronics. The working fluid was R-134a and the investigation was conducted for a nominal outlet saturation temperature of 30 ∘C. The microchannels were 1 cm long and covered a square footprint area of 1 cm2. Boiling curves starting at low vapor quality and average heat transfer coefficients were obtained for nominal channel mass fluxes from 250 kg/m2s to 1100 kg/m2s. The measurements were conducted by gradually increasing the power dissipation over a serpentine heater soldered at the bottom of the multi-microchannels, until a maximum heater temperature of 150 ∘C was reached. Infrared thermography was used for the heater temperature measurements, while high-speed imaging through a transparent top cover provided visual access over the entire length of the channels. The average heat transfer coefficient increased with the dissipated heat flux until a decrease dependent on hydrodynamic effects occurred, possibly due to incomplete wall wetting. Depending on the channel geometry, a peak value of 200 kW/m2K for the footprint heat transfer coefficient and a maximum dissipation of 620 W/cm2 at the footprint with a limit temperature of 150 ∘C could be obtained, showing the suitability of the investigated geometries in high heat flux cooling of power electronics. The experimental dataset was used to assess the prediction capability of selected literature correlations. The prediction method by Bertsch et al. gave the best agreement with a mean absolute percent error of 24.5%, resulting to be a good design tool for flow boiling in high aspect ratio multi-microchannels as considered in this study.

EVALUACIÓN DEL COMPORTAMIENTO MECÁNICO DE BARRERAS TÉRMICAS MEDIANTE TÉCNICAS DE EMISIÓN ACÚSTICA

To develop more efficient turbines, it is necessary to increase the inlet temperature and / or decrease the temperature losses for these reasons it is necessary to develop materials resistant to higher temperatures and with lower heat transfer coefficients. A technological solution to this problem is the implementation and subsequent improvements of thermal barriers coating (TBC). In general, these TBCs are composed of a ceramic coating and an intermetallic layer that serves as a bond coat between the ceramic and the substrate to be protected. The Y2O3 stabilized ZrO2 (Y-TZP), is one of the ceramics used as TBC. However, the thermomechanical fatigue to which these barriers are subjected causes them to deteriorate, forming cracks and / or delaminations. One way to counteract this effect is the addition of an agent that allows self-healing, that is, as a crack in the barrier occurs, at the same time, the recovery of this defect is generated as a result of temperature, diffusion and / or self-healing reaction. The aim of this work is the study by acoustic emission AE of the mechanical behavior of the TBCs with the addition of SiC in the suspension of Y-TZP / Al2O3. In the same way, a microstructural analysis and a finite elements model was carried out in order to compare results. The coatings were made by Suspension Plasma Spray (SPS) on metal plates of 70x10x2 mm, an intermetallic was deposited as a bond coating and finally a coating of Y-TZP / Al2O3 with and without 15% wt SiC. The AE becomes a fundamental tool in the study of the mechanical behavior of thermal barriers. The use of wavelet transforms streamlines the study and analysis of recorded sound spectra. The cracks generation arises at very low stress levels.

Louver and effusion cooling heat transfer for a double wall effusion plate with impingement jet array coolant supply

Louver slot cooling is employed, which consists of an aligned collection of film cooling holes, contained within a specially-designed device which concentrates, and directs the coolant from a slot, so that cooling air then advects as a layer downstream along the test surface. This louver-supplied coolant is then supplemented by coolant which emerges from different rows of downstream film cooling holes. Coolant for both cooling arrangements is supplied using an array of impingement jets. Experimental data are provided for a mainstream Reynolds number Rems range of 168,000–181,000. Full-coverage film cooling initial blowing ratio values are 2.5, 3.2, 4.4, and 5.2, with respective louver slot blowing ratios of 1.2, 1.5, 2.1, and 2.4. Measured lateral-averaged adiabatic effectiveness results show that, with impingement supply cooling only, for blowing ratios of 4.4 and lower, the louver and effusion cooling arrangement generally provides higher effectiveness, relative to an effusion cooling only arrangement. For all blowing ratios considered, another advantage of the louver slot is more uniform values of increased effectiveness along the entire test surface, including locations which are just downstream of the slot. Relatively weak dependence on blowing ratio is present for the louver and film cooling arrangement, in contrast to the effusion only configuration, where effectiveness data generally increase progressively and substantially (at most x/de locations) as the blowing ratio becomes larger. Lateral-averaged heat transfer coefficient values for the effusion cooling only arrangement, and for the louver and effusion cooling arrangement, are approximately quantitatively similar when the blowing ratio is 4.3 to 4.4. Data for blowing ratios BR of 5.2 to 5.5 show that the louver and effusion cooling gives much lower lateral-averaged heat transfer coefficients, compared to the effusion cooling only arrangement. This is a result of reduced local turbulent thermal transport levels within the wake flows which are present downstream of the louver leap device.

Influence of SiC Addition on Mechanical Behavior of Thermal Barriers with the Aid of Acoustic Emission

The improvement of high temperature materials with lower heat transfer coefficients lead to the development of thermal barrier coatings (TBCs). One of the most widely used materials for thermal barrier coatings is Y2O3 stabilized ZrO2 (Y-TZP) because of its excellent shock resistance, low thermal conductivity, and relatively high coefficient of thermal expansion. The aim of this work is to study the TBCs mechanical behavior with the addition of SiC into the suspension of Y-TZP/Al2O3 by acoustic emission (AE). Additionally, a microstructural analysis and a finite elements model were carried out in order to compare results. The coatings were made by suspension plasma spray (SPS) on metal plates of 70 × 12 × 2 mm3. An intermetallic was deposited as a bond coating, followed by a coating of Y-TZP/Al2O3 with and without 15 wt.% SiC, with thicknesses between 87 and 161 μm. The AE becomes a fundamental tool in the study of the mechanical behavior of thermal barriers. The use of wavelet transforms streamlines the study and analysis of recorded sound spectra. The crack generation arises at very low stress levels.

Verification of Similarity of Scaling Laws in Tunnel Fires with Natural Ventilation

Scaling laws based on the conservation of the Froude number have been widely used in both fire research and fire engineering design in tunnels. However, the applicability of scaling laws in tunnel fires with natural ventilation has not been systematically verified. In order to verify the scaling laws for tunnel fires with natural ventilation, two model tunnels were tested: Tunnel-L, measuring 20 m long, 0.9 m wide and 0.46 m high, representing the prototype tunnel, and Tunnel-S, measuring 10 m long, 0.45 m wide and 0.23 m high, representing a ½-reduced-scale tunnel. Both tunnels were made of material with a very low heat transfer coefficient, thus heat loss at the boundaries was negligible. The first series of fire tests, with heat release rates of 15.8 kW, 31.6 kW and 63.2 kW, was conducted in Tunnel-L and the second series of fire tests, with heat release rates of 2.8 kW, 5.6 kW and 11.2 kW, was conducted in Tunnel-S. The experimental results showed that compared to the physically measured data in Tunnel-L, the data deduced from Tunnel-S based on scaling laws could lead to a significant under-estimation of the peak temperature rises along the tunnel with errors as high as 50 ~ 70%, except those above the fire sources, and a remarkable over-estimation of smoke concentrations. The study demonstrated that scaling laws could be invalid for tunnel fires with natural ventilation and that results measured in reduced-scale tunnels should be further verified when applied to full-scale prototypes.

Investigation of Ethylene Glycol Heat Transfer Coefficient Trough Double Pipe and Coil Heat Exchanger

The research objective is to assemble a convection test system which acts as a heat exchanger (HE) and test its applicability using ethylene glycol. A Double Pipe (DP)-type HE consists of an inner pipe surrounded by an outer pipe (annulus) whereas a Coil-type HE composed of a coil surrounded by an outer pipe. Water flows through the outer pipe in both types of HE, while ethylene glycol flows through the inner piper or coil. HE in combination with other components (such as) forms a convection test system. The applicability of the system was tested to determine the heat transfer coefficient of ethylene glycol in a DP-type and Coil-type HEs. After that, the heat transfer rate was calculated and compared. The results show that the heat transfer coefficient in the DP-type HE is the lowest at 12.2 W/m2 oC and the highest at 26.8 W/m2 oC; and the corresponding heat transfer rate is the lowest at 8.3 W and the highest is 56.3 W. In comparison, for Coil-type HE, the lowest heat transfer coefficient is 38.9 W/m2 oC and the highest is 66.2 W/m2 oC which correspond to the heat transfer rate 19.9 W at the lowest and 225 W at the highest.

Increasing the efficiency of heat and mass exchange in an improved rotary film evaporator for concentration of fruit-and-berry puree

An improved model of a rotary film evaporator with a cutting blade having a reflective surface and equipped with an autonomous heating system which is fed by a power supply from Peltier elements. The reflective surface of the advanced cutting blade had an area of 0.06 m 2 and was heated by a flexible film resistive electric heater of radiating type with a ~15...20 W power supply. This solution provides additional heating and mixing and helps to capture the cut-off layer of puree while reducing the useful surface of the working chamber by 7 %. Most evaporators have a low heat transfer coefficient reducing the energy content of the process and final quality of the product. The heat exchange efficiency can be increased by improving the design of the film-forming element of the rotary film evaporator. The use of the proposed cutting blade with a reflective surface enables an increase in the heat transfer coefficient by approximately 20 % compared to the basic rectangular blade design. When comparing the calculated data, it can be concluded that the main indicator of resource efficiency, namely specific energy consumption for heating a unit volume of product in the RFE amounts to 408 kJ/kg compared to 1,019 kJ/kg with the basic vacuum evaporator which means a 1.97 times consumption reduction. The duration of heat treatment in the RFE is 60 s compared to 1 h in the basic VE which shows a significant reduction of raw material exposure to high temperatures. The obtained data show the effectiveness of engineering and technological solutions. The engineering and technological component of any heat and mass exchange processes, in particular the concentration of fruit-and-berry raw materials, is the main component in the production of semi-finished food products of a high degree of readiness

Thermal and Mechanical Analyses of Compliant Thermoelectric Coils for Flexible and Bio-Integrated Devices

AbstractThree-dimensional coil structures assembled by mechanically guided compressive buckling have shown potential in enabling efficient thermal impedance matching of thermoelectric devices at a small characteristic scale, which increases the efficiency of power conversion, and has the potential to supply electric power to flexible bio-integrated devices. The unconventional heat dissipation behavior at the side surfaces of the thin-film coil, which serves as a “heat pump,” is strongly dependent on the geometry and the material of the encapsulating dissipation layer (e.g., polyimide). The low heat transfer coefficient of the encapsulation layer, which may damp the heat transfer for a conventional thermoelectric device, usually limits the heat transfer efficiency. However, the unconventional geometry of the coil can take advantage of the low heat transfer coefficient to increase its hot-to-cold temperature difference, and this requires further thermal analysis of the coil in order to improve its power conversion efficiency. Another challenge for the coil is that the active thin-film thermoelectric materials employed (e.g., heavily doped Silicon) are usually very brittle, with the fracture strain less than 0.1% in general while the overall device may undergo large deformation (e.g., stretched 100%). Mechanical analysis is therefore necessary to avoid failure/fracture of the thermoelectric material. In this work, we study the effect of coil geometry on both thermal and mechanical behaviors by using numerical and analytical approaches, and optimize the coil geometry to improve the device performance, and to guide its design for future applications.

Numerical Study on Regenerative Cooling Characteristics of Kerosene Scramjets

The use of kerosene-based regenerative cooling for scramjet has been found widespread attention due to its inherent nature of high energy utilization efficiency and good thermal protection performance. In order to provide a reference for the later design and experiments, three-dimensional turbulence simulations and sensitivity analysis were performed to determine the effects of three operating mode parameters, heat flux, mass flow rate, and outlet pressure, on the regenerative cooling characteristics of kerosene scramjets. A single rectangular-shaped channel for regenerative cooling was assumed. The RNG k-ε turbulence model and kerosene cracking mechanism with single-step global reaction were applied for the supercritical-pressure heat transfer of kerosene flows in the channel. Conclusions can be drawn that as the kerosene temperature rises along the channel, the decrease of fluid density and viscosity contributes to increasing the fluid velocity and heat transfer. When the kerosene temperature is close to the pseudocritical temperature, the pyrolysis reaction results into the rapid increase of fluid velocity. However, the heat transfer deterioration occurs as the specific heat and thermal conductivity experience their turning points. The higher heat flux leads to lower heat transfer coefficient, and the latter stops rising when the wall temperature reaches the pseudocritical temperature. The same rising trend of the heat transfer coefficient is observed under different outlet pressures, but the heat transfer deterioration occurs earlier at smaller outlet pressure for the reason that the corresponding pseudocritical temperature decreases. The heat transfer coefficient increases significantly along with the rise of the mass flow rate, which is mainly attributable to the increase of Reynolds number. Quantitative results indicate that as the main influence factors, the heat flux and mass flow rate are respectively negatively and positively relative to the intensification of heat transfer, but outlet pressure always has little effects on cooling performance.

Viscous dissipation and joule heating effect on MHD flow and heat transfer past a stretching sheet embedded in a porous medium

An analysis is made to illustrate the MagnetoHydroDynamics (MHD) flow and gradient heat transport of a Newtonian fluid over a stretching sheet embedded in a porous matrix. The governing nonlinear partial differential equations are reconstituted as ordinary differential equations utilizing suitable similarity transformation and then treated numerically using 4th order Runge-Kutta method along with shooting technique and analytically by Homotopy Perturbation Method. The verification of present study with earlier works serves as the benchmark of reliability of the present study. The important outcomes of this study are: porous parameter (Kp) acts as aiding force i.e when Kp is increased from 0.1 to 10 gradually there is a significant growth in velocity and after that rate of increment gets slowdown, greater Eckert number and joule heating parameter cause a rise in temperature as well as enhance the thermal boundary thickness. Consequently rate of heat transfer diminishes as thickness leads to low heat transfer coefficient. The applications of this study are shown in: multiple heating devices and industrial processes such as incandescent light bulb's filament emitting light, food processing and polymer processing etc.

Effects of Fluid Flow Characteristics and Heat Transfer of Integrated Impingement Cooling Structure for Micro Gas Turbine

Gas turbine is one of the important sources of energy which combust a combination of fuel and compress air to produce a mechanical work that will be converted into electrical energy. Efficiency of gas turbine can be increased by raising the Turbine Inlet Temperature (TIT). The problem is current trend of TIT already exceed the allowable melting point temperature of metal blade material. The current turbine blade can withstand its high temperature by adding jet impingement cooling structure into turbine blade. The purpose of this research is to investigate the effect of combination two different stand-off distance ratio, Y/D towards the heat transfer coefficient of the target plate by using Ansys FLUENT Computational Fluid Dynamics (CFD). Combination of stand-off distance ratio, Y/D = 1.5&3.0 gave 2nd highest heat transfer coefficient on the target plate next to the original stand-off distance ratio, Y/D = 1.5 with only a slightly different in value. By combining two different stand-off distance ratio, Y/D in a set of arrays, it can affect the heat transfer coefficient on the target plate. It seems that the combination of stand-off distance may improve the performance of heat transfer coefficient of turbine blade that have relatively lower heat transfer coefficient and may be detrimental to the performance of heat transfer coefficient that have a relatively high heat transfer coefficient.

Optimization of cooling conditions to avoid surface cracks in Direct Chill casting of Cu-Fe-P alloy

The industrial production of Cu-Fe-P billet Direct Chill (DC) casting exhibits often difficulties related to the generation of surface cracks on the cast piece. The demand for always higher productivity leads to increased casting speed with significant cooling requirements. This in turn affects the thermal gradient within the billet leading often to stress concentration responsible for surface cracking. In order to deal with this issue while keeping productivity at high levels lowering the industrial cost, a 2D thermo-mechanical Finite Element (FE) model was developed, which was applied and validated based on industrial conditions. The model targets to predict the material failure during DC casting. Based on the proposed approach the billet’s temperature profile and its stress state during secondary cooling are calculated. The simulation results revealed that strong cooling using water jets cannot be applied immediately at the exit of the mold at any casting speed. However, as the distance of the secondary cooling unit from the mold exit increases, the stress concentration drops significantly, so that the jet nozzles can be applied from 750 to 2500 mm away from the mold, depending on the casting speed, without material failure. On the contrary, milder water spraying applying a lower local heat transfer coefficient, but on the same time covering broader impact surface, can result in a more efficient billet cooling. Thus, due to milder cooling the cast-piece material is less prone to failure and cooling can be applied immediately at the mold exit. Furthermore, a sequence of numerous spray arrays can further increase the cooling capacity. Concluding, it is shown that a validated thermo-mechanical 2D FE model can provide deeper insights used industrially as a setting tool, which optimizes the casting conditions in order to further improve productivity and the quality characteristics of the as-cast billet.

Fabrication of Fe‒Al Coatings with Micro/Nanostructures for Antifouling Applications

Fouling is one of the common problems in heat-transfer applications, resulting in higher fouling resistance, and lower heat-transfer coefficient. This paper introduces the design and fabrication of an Fe–Al coating with micro/nanostructures on low-carbon steel by electrical discharge coating (EDC) technology to improve the antifouling property. The Fe–Al coating with micro/nanostructures is characterized by a large number of micro/nanostructures and superior anti-fouling property, which is attributed to its hydrophobic surface. The antifouling property, fouling induction period and contact angle of the Fe–Al coating with micro/nanostructures increase with the increasing gap voltage. Compared with the polished surface of low-carbon steel, the Fe–Al coating with micro/nanostructures extends the induction period from 214 to 1350 min, with a heat flux of 98 kW·m−2. After 50 adhesion tests, the contact angle of the Fe–Al coating with micro/nanostructures decreases from 6.81% to 27.52%, which indicates that the Fe–Al coating with micro/nanostructures is durable and suitable for industrial applications.