Pitch Distance Research Articles

Computational Analysis of Flow Around Two Wall-Mounted Trapezoidal Bluff Bodies Arranged in Tandem Position

Abstract Flow around two identical wall-mounted trapezoidal bluff bodies, arranged in tandem, is numerically investigated at a Reynolds number of 750,000. The investigation employs Reynolds-averaged Navier–Stokes (RANS) equations and the k–ω SST turbulence model. The effect due to the change of the angular orientation of the inclined faces (α) of this bluff body and the pitch distance (L/D) on hydrodynamic quantities and turbulence quantities is investigated. Furthermore, the drag coefficient and Strouhal number have also been evaluated to understand the vortex shedding and flow pattern-related phenomena. For d and intermediate types of bluff bodies, the streamwise mean velocity, cross-stream mean velocity, turbulence kinetic energy, and recirculation length decrease with the increase of α or L/D. Significant changes are also observed in the case of Strouhal number. Reduction in drag coefficient and recirculation length is observed with increased L/D at a constant α for d-type bluff bodies. The change of α and L/D also creates the formation of a periodic von Kármán vortex street at downstream of the second bluff body in the case of L/D = 7, making the flows more complex and unstable. The maximum size of the recirculation bubble occurs in the case of L/D = 10 at α = 30 deg. The investigation provides valuable insight into the complex dynamics of tandem configurations of wall-mounted bluff bodies.

Enhancing tribological performance of AISI 52100: the role of laser surface texturing in dry and lubricated conditions

Abstract Laser surface texturing (LST) is a valuable technique in surface engineering that offers significant improvements in the tribological behavior of metals and alloys. This study investigates the synergistic effect of incorporating hexagonal boron nitride (h-BN) as a solid lubricant with laser surface texturing on the tribological performance of AISI 52100. Dimple textures with varying pitch distances (100, 150, and 200 μm) were created on the surfaces of the mentioned materials using LST. The friction coefficient and wear behavior of both non-textured surface (NTS) and textured surfaces (TS) were analyzed under dry sliding (DS) and lubricating sliding (LS) conditions. Wear tests were conducted using a universal tribometer under a load of 10 N, a sliding frequency of 10 Hz, and a sliding time of 1250 s. The results demonstrate that the presence of dimple textures significantly influences the tribological behavior of the materials. In DS, the wear coefficient exhibits a significant reduction compared to NTS, with decreases of 88.1% for TSP-100, 28.5% for TSP-150, and 76.1% for TSP-200. In LS, the TSP-L-100 (h-BN NPS) surface demonstrates the lowest average wear coefficient among all textured surfaces. Specifically, the TSP-L-100 surface shows a remarkable 97.61% reduction in average wear coefficient compared to NTS. This study demonstrates the potential of LST combined with h-BN as a solid lubricant in improving the tribological properties of metals, offering valuable insights for surface engineering applications in various industries.

Group resistances of tensile-loaded anchored-bolted connections with CFST columns: Tests, simulations, and theoretical models

The performance of the connections in concrete-filled steel tubular (CFST) columns fabricated with a group of two anchored blind-bolts under tensile forces is evaluated. Based on the bolt group arrangement, two sets of experiments, comprising eight full-scale specimens, were tested. Test parameters include the presence of concrete, bolt anchorage length, pitch distance, and gauge distance. Further, numerical models were developed, which, after validation, were used for parametric studies. Key findings indicate that bolt gauge distance, anchorage length, concrete grade, and column cross-section slenderness significantly influence the connection behaviour, but pitch distance has the least influence. Tube and concrete failure modes, as well as critical gauge and pitch distances, are identified, which govern tube deformation and concrete crushing zones. Finally, a bi-linear theoretical model is developed that can provide a fair prediction of the connection strength and stiffness.

A Study on the Manufacture of CNT Composites Bipolar Plate for the Fuel Cell Using a Nanosecond Pulsed Laser

The channels of the graphite-based bipolar plate for hydrogen fuel cells were mainly manufactured through milling due to low forming elongation and processability. However, during the milling process, the machining precision is low due to tool wear and vibration, and there is a risk of breakage. Non-traditional laser processing can solve the problems of tool wear and vibration through non-contact processing. In this study, the interaction characteristics of the nanosecond pulsed laser and CNT composites were observed, and channels and bipolar plates were manufactured. The effect of scanning speed and pulse duration was observed for interaction characteristics. Defects were observed due to high thermal effects at low scanning speed and high pulse duration. Channels were created depending on parallel pitch distance [] and Number of scans (NOS). The channel was evaluated for depth, top width, bottom width, channel angle, material removal rate, and surface roughness, and significant changes were observed depending on . The chemical composition, surface resistance, and contact angle of the laser-processed channel were measured. The laser processed channel was oxidized, and the surface resistance and contact angle increased. Finally, the manufacturability of the CNT composites bipolar plate using laser was examined.

Impact of Toolpath Pitch Distance on Cutting Tool Nose Radius Deviation and Surface Quality of AISI D3 Steel Using Precision Measurement Techniques.

The selection of the right tool path trajectory and the corresponding machining parameters for end milling is a challenge in mold and die industries. Subsequently, the selection of appropriate tool path parameters can reduce overall machining time, improve the surface finish of the workpiece, extend tool life, reduce overall cost, and improve productivity. This work aims to establish the performance of end milling process parameters and the impact of trochoidal toolpath parameters on the surface finish of AISI D3 steel. It especially focuses on the effect of the tool tip nose radius deviation on the surface quality using precision measurement techniques. The experimental design was carried out in a systematic manner using a face-centered central composite design (FCCD) within the framework of response surface methodology (RSM). Twenty different experiment trials were conducted by changing the independent variables, such as cutting speed, feed rate, and trochoidal pitch distance. The main effects and the interactions of these parameters were determined using analysis of variance (ANOVA). The optimal conditions were identified using a multiple objective optimization method based on desirability function analysis (DFA). The developed empirical models showed statistical significance with the best process parameters, which include a feed rate of 0.05 m/tooth, a trochoidal pitch distance of 1.8 mm, and a cutting speed of 78 m/min. Further, as the trochoidal pitch distance increased, variations in the tool tip cutting edge were observed on the machined surface due to peeling off of the coating layer. The flaws on the tool tip, which alter the edge micro-geometry after machining, resulted in up to 33.83% variation in the initial nose radius. Deviations of 4.25% and 5.31% were noted between actual and predicted values of surface roughness and the nose radius, respectively.

Improving the thermal performance of vertical ground heat exchanger by modifying spiral tube geometry: A numerical study

Ground heat exchanger (GHE) is the most crucial element of a ground source heat pump (GSHP) system for building cooling and heating by the utilization of geothermal energy. Therefore, intending to enhance the performance of GHE, the present study conducts a computational investigation of the thermal performance of modified spiral tube vertical GHEs. Several modifications of uniform-pitched spiral GHE are made to increase its thermal performance. Some modifications are introduced as variable-pitched spiral tube GHE where spiral inlet pipes are densified in the lower part of GHEs by reducing pitch distance. Conversely, in some modifications, the position of the outlet straight pipe is changed. Water is considered as the working fluid and the inlet temperature of the water is maintained fixed at 300.15 K. After extensive analysis, it is evident that, when the outlet pipe is placed outside of the spiral coil, there is a 7.67 % enhancement in the thermal performance than a traditional uniform-pitched spiral tube GHE. However, modifications like variable-pitched spiral tube GHEs are not significant to improve the thermal performance due to the quick saturation of the ground soil temperature around the GHE pipes. To have a balance between heat transfer rate and pressure drop, thermal performance capability (TPC) and coefficient of performance improvement (COPimprvt) criterion were evaluated and it is found that the uniform-pitched spiral tube GHE along with the outlet pipe at the outside of the spiral provides maximum thermal performance with a maximum TPC value of 1.062 and provides the positive value of COPimprvt criterion. The positive values of COPimprvt indicate that the spiral tube GHEs are energy efficient based on heat transfer and pressure drop. Moreover, spiral GHE with high-density polyethylene (HDPE), concrete pile, and sandy clay outperform the other materials for pipe, backfill, and soil, respectively. Specifically, HDPE pipe, concrete backfill, and sandy clay as soil offer around 7 %, 5 %, and 7.8 % higher thermal performance compared to polyethylene, sand silica, and clay, respectively.

The role of cavity shapes in improving the performance of a heat sink incorporating nano-enhanced phase change material

Improving the cooling performance of heat sink is critical for providing better thermal management to compact electronic devices. Thus, analyzing various cavity shapes for a heat sink containing Nano-enhanced Phase Change Material is of utmost necessity. The present study focuses on a two-dimensional conjugate heat propagation in a Heat sink with Rectangular (HRC), Trapezoidal (HTC), and Wavy (HWC) cavities. Various cavity shapes are examined to identify the ideal shape for a heat sink containing nano-enhanced Phase Change Material (Ne-PCM). The copper oxide (CuO) nanoparticle enhanced paraffin is considered as Ne-PCM. The analysis encompasses identification of the potent cavity shape, its optimum geometric parameters, the dominant mode of heat transfer and ultimately the desirable thermophysical properties of the Ne-PCM. Among HRC, HTC, and HWC, the heat sink with HRC performs the best by maintaining the lowest base temperature. The HTC, has a better initial performance than the HRC, though HTC has low PCM content. Nevertheless, as time progresses, HTC fails to inhibit the base temperature rise. In contrast, due to increased contact surface area, PCM in HWC experiences a stronger opposing viscous force. Consequently, HWC has conduction-dominated heat transfer and the slowest melting of PCM that elevates the base temperature, accumulating heat near cavity walls. Shortening the relative pitch distance and elongating the relative height of the HRC further lowers the base temperature of the heat sink. Notably, the heat transfer mode analysis reveals that in the cavity with maximum height, heat diffusion dominates convective heat transfer. Heat diffusion increases away from the cavity walls towards the middle of the cavity. Ultimately, it is noted that a denser PCM with high thermal conductivity and low viscosity effectively maintains a low heat sink base temperature. A denser PCM imparts more sensible and latent heat absorption capability and maintains a lower base temperature. On complete melting, the convective heat transfer is much higher in a denser PCM. A PCM with higher thermal conductivity marginally lowers the base temperature with a small increase in PCM melting rate.

Rough bed hydrodynamics under wave-current interactional flow field: double averaging approach

ABSTRACT The effect of surface wave on the double-averaged (DA) current-only flow properties is examined over two different types of rough beds comprising hemispherical elements with regular and staggered arrangements. For each case, the relative roughness spacing of p/r = 4 is maintained, where p = pitch distance and r = hemisphere height. The changes in turbulence characteristics against the water depth are analysed for superimposed surface waves propagating along the current with 1 and 2 Hz frequencies. The effect of regular and staggered roughness arrangements on different turbulence characteristics is explored. Results demonstrate that the DA stream-wise velocity decreases and increases at the outer region and within the roughness region, respectively, due to wave propagation. Owing to the surface wave, the DA intensity and form-induced intensity increase above the roughness layer and decrease within the bottom boundary layer. The values of form-induced intensities are smaller (greater) than the DA turbulence intensities at each considered flow depth within the roughness (outer) layer. For the entire flow depth, the values of DA Reynolds stress decrease due to wave interactions along a steady current. Again, the turbulence is observed to be close to isotropic for the current-only flow at the outer zone, while the flow transits to an anisotropic state with wave imposition on current. Further, the computed values of the turbulence indicator and dispersion functions are used for the identification of the level of turbulence and dispersion at each flow depth for the locations upstream and downstream of a hemisphere in the hemispherical bed.

Elimination of splash damage for smaller scribe widths in next-gen memory devices via stealth dicing

Scattered light damage (splash) is one of the common defects that can be observed from the stealth dicing process, and it is mainly due to the interaction of the pulsed laser beam with the micro-crack and modified layer formed. This might cause thermal damage on the active layer of the die and degrade the reliability and yield of the device. The development of new technology node for memory devices aims to reduce scribe width, thereby increasing the number of dies per wafer. The ongoing trend towards scribe width reduction from 120 μm to current sub-60 μm, results in increased throughput and decreased cost per die. Furthermore, this reduction allows for greater functionality integration within a confined space, thereby enhancing overall device performance. Hence, the elimination of splash during the SD process is imperative to enable further shrinking of scribe width. This paper focuses on the impact of pulse pitch and distance from 1st focal depth to silicon (Si) frontside on the maximum splash distance. Lower pulse pitch and lower distance from 1st focal depth to Si frontside will introduce higher splash distance. An empirical model for splash elimination was established to determine the critical distance from 1st focal depth to Si frontside as a function of pulse pitch.

Numerical analysis of a solar air heater with offset transverse ribs placed near the absorber plate

Solar air heater (SAH) is used to convert readily available solar energy into useful thermal energy. Several studies have been conducted with different roughness elements on the absorber plate. However, study with ribs which are placed slightly above the heated plate, termed as offset transverse ribs, are still scant in the literature. Such study would explain the effect of flow between the ribs and the absorber plate on heat transfer augmentation in a SAH. With this objective a 2-D numerical study is performed here by solving steady RANS equations with RNG k−ɛ turbulence model. The effect of offset transverse ribs on heat transfer, pressure drop and thermal enhancement factor (TEF) is investigated. The geometrical parameters, such as, relative gap (α), relative height (β) and relative pitch (λ) are varied in the range of 0.0–0.045, 0.015 to 0.09, and 0.0333 to 0.1, respectively. The performance of SAH is evaluated on the basis of highest enhancement in relative Nusselt number (NuR/Nu) and thermal enhancement factor (TEF). A slight gap between the ribs and the absorber plate (α = 0.0075) is observed to yield better thermal performance than that for the attached ribs (α = 0). The maximum enhancement in NuR/Nu is found to be 1.52 for α = 0.0075. However, increasing the gap (i.e., α) prevents the flow reattachment with the absorber plate. Increase in rib height, on the other hand, is found to be more effective in heat transfer enhancement, but with a price of a significant enhancement in pressure drop. This leads to a reduction in the overall performance of SAH. Increment in pitch distance, however, reduces the enhancement in both Nusselt number and friction factor. By considering these three parameters, the highest TEF is found to be 1.042 for α=0.0075, β=0.030, and λ=0.0333 at Re equal to 13000. Finally, correlations for NuR and fR are derived as a function of the parameters investigated for helping the design of SAHs.

Numerical assessment of solar air heater performance having a broken arc and broken S-shaped ribs as roughness

This research article aims to provide a detailed numerical study of the multifaceted impact of S-shaped and broken arc roughness on solar air heaters. Therefore, a strong comparison was made between the modified heaters and smooth heaters for Reynolds numbers ranging from 2 00022 000. Also, the impact of two parameters, i.e. pitch and gap was analyzed to optimize the performance of the heater. The gap varies from 0.3 mm to 0.9 mm in both types of ribs with a step size of 0.2 mm. Afterwards, the pitch distance between both types of roughness was varied from 15 mm to 25 mm in the step size of 5 mm. Notably, it has been observed that among all the considered configurations, the gap length of 0.9 mm and pitch length of 25 mm have shown significant improvements in heat transfer characteristics. The specific combination of the gap of 0.9 mm and pitch of 25 mm has demonstrated better heat transfer capabilities at the expense of an increased friction factor. Lastly, the thermal performance factor of the systems was analyzed and reported. It was reported that the pitch length of 25 mm and gap length of 0.9 mm have shown a maximum thermal performance factor value from 2.9 to 3.3, while the pitch length of 25 mm and gap length of 0.3 mm have depicted the lowest thermal performance factor value. In terms of the overall performance, i.e. the thermal performance factor, the combination with a gap of 0.9 mm and pitch of 25 mm has shown the best performance, while a gap of 0.3 mm and pitch of 25 mm has yielded the worst performance.

An experimental study of the flow structure in arrays of cold bidirectional swirling jets

Jets arrays have become a promising technology for industrial applications, including heat transfer and combustion processes. This paper presents the first experimental results of arrays of bidirectional swirling jets, including their flow structures and specific turbulent interactions. Particle image velocimetry of non-reacting linear arrays showed the formation of recirculation zones within each jet of the array. These regions are the most stable, with fluctuations less than 0.002 of the bulk inlet velocity Vin. In addition, jets merging locations also show a significant decrease in velocity fluctuations, with values V′/Vin < 0.005, which is most clearly seen at a smaller pitch distance. However, the highest turbulent fluctuations occur in shear layers, reaching values of V'/Vin ≈ 0.02 for linear arrays and V'/Vin ≈ 0.03 for planar configurations. The flow structure of planar arrays is more complex, leading to the formation of secondary vortex structures at locations of jet interaction. This results in a significant decrease in the flow swirl number, from an initial value of Sin = 2.1 in the vortex chamber, to S1 = 0.36–0.49 at z/dout2 = 1 and S2 = 0.19–0.27 at z/dout2 = 2 beyond the outlet nozzle. Strong cross-sectional motions are observed in planar arrangements, leading to the development of additional regions of negative axial velocity between the outlet nozzles. The boundaries of these regions have nearly zero axial velocity values and can provide reliable ignition and flame stabilization in the case of reactive bidirectional jets. Therefore, the flow structure in planar arrays forms a large stabilization zone, and the obtained results can be used to develop a new multipoint combustion technique.

STensile behaviour of T-stub to hollow section column using elliptical-head one-side bolts

The Elliptical-head one-side bolt (EOB) is a typical representative of the third generation for one-side bolts, relying on its elliptical head and bolt hole to achieve orthogonal anchorage, and the application scenario is mainly the bolted connection of closed-section members. Studies have been reported for the shear performance of EOBs bolted lap connections and the tensile behaviour of concrete-filled steel tubes, but there is still a lack of the tensile performance of EOBs connecting Hollow section columns (HSCs), which is necessary for the application of the component method for the beam-column joints design. Therefore, numerical simulation and theoretical analysis methods were employed in this paper to demonstrate the feasibility of adopting EOBs for this type of connection, including typical failure modes, novel yield line pattern in the HSC wall, comparison with the Conventional high-strength bolt (CHB) connections, analysis of the parameters related to the elliptical bolt head and hole, and the establishment and validation of the methodology for calculating the HSC bearing capacity. The results show that: The novel trapezoidal yield line pattern tended to show in the HSC wall with the smaller bolt pitch distance and larger gauge distance; The yield strength of the EOBs bolted T-stub to HSC connections was reduced by about 15% compared to the CHBs bolted ones; Vertical layout of bolt holes, accuracy of rough assembly, rotation deviation of bolt shank within 20° and avoidance of bolt offsets in bolt hole were recommended for EOB connections; The novel yield line pattern established in this paper predicted the yield strength of the connections, and the accuracy and stability were verified by comparing with finite element modelling (FEM) results.

The Effect Of Pitch Ratio On Screw Turbine Performance With Tip Fin

A water turbine is an energy conversion machine that converts water head into shaft movement. In screw-type turbines, performance is influenced by several parameters including outer diameter, inner diameter, rotor length, head angle, number of blades, and pitch distance. This research uses a screw turbine type with a tip fin. The research aims to determine the performance of screw turbines with tip fins on mechanical power and efficiency. The research independent variables consist of pitch ratio and flow rate. The pitch ratio variations used are 1.2; 1.4 and 1.6 while the variations in flow rate used are 3 l/s, 3.5 l/s, and 4 l/s. The method used in this research is experimental. This study's data analysis employed the two-way Anova method with an alpha (α) of 5%. Anova's results show that the P-value of the interaction of the two independent variables, pitch ratio and water discharge, is <0.05, meaning that the independent variables have a significant influence on the performance of the screw turbine. The highest turbine performance results were at a pitch ratio of 1.4 at a water flow rate of 4 l/s resulting in an efficiency value of 34.91% and a mechanical power value of 6.82 watts at a rotational speed of 125 RPM. The lowest turbine performance results at a pitch ratio of 1.2 with a flow rate of 3 l/s resulting in an efficiency of 22.64% and a mechanical power of 3.32 watts at a rotational speed of 56 RPM.

Experimental Analysis of Fin Pitch Distance Variation of Adsorber for Adsorption Chiller Performance

The purpose of this study was to study the performance of silica gel-air adsorption chiller on two types of adsorber fins by conducting experiments at several cycle times, namely 500, 600, 700 and 800 seconds with specific mass recovery times, heat recovery times, and also variations on the input of the cooling fluid, so that optimal cycle times can be obtained related to COP and SCP. The adsorber fin-spacing which has more tightly fin distance does not determine the better performance of the adsorber for chiller application because the shorter distance of the fin, the cross-sectional area of the silica gel surface that has initial contact with the adsorbate will decrease so that the performance of the adsorber will decrease. The highest cooling capacity and COP obtained are 3.1 kW and 0.52, respectively. The results are obtained on adsorber with 3 mm fin distance and 700 s cycle with hot water inlet temperature of 79°C, cooling water inlet temperature of 29.4°C and chilled water outlet temperatures of 8.5°C

Effect of hemispherical roughness spacing on double-averaged turbulence characteristics for different flow submergence

The double-averaged (DA) turbulence characteristics over rough bed comprising of hemispherical elements with different spacing ( p/ r = 2, 4, 6, and 8; p = pitch distance; r = height of hemisphere) is quantified for three flow-submergences ( h/ r = 7.14, 5.35, 3.57; mean flow-depth ( h) = 20 cm, 15 cm, and 10 cm). The production and dissipation rates of turbulent kinetic energy are maximum at and below the crest level. Within interfacial sublayer, the degree of anisotropy is observed to be maximum for p/ r = 4 and the tendency for the return to isotropy is strongest for p/ r = 8 in the outer layer. The turbulence generated in the bottom region is still present in the outer region for low flow-submergences. The turbulence strength is maintained in the roughness order (descending) as p/ r = 4 > 2 > 6 > 8 > plane bed; wherein the change in flow-submergence does not change this order.

Thermo-hydraulic Analysis of Fluid Flowing Through Circular Pipe with Wire Mesh Inserts having Varying Mesh Porosity

The experimental investigation was made to analysis the rate of heat transfer of fluid flowing through a heat exchanger with varying wire-mesh porosity inserts. The Nusselt number (Nu), friction factor (f), and overall heat transfer rate (Q) were evaluated using experiments. Three different wire mesh inserts of square, hexagonal and diamond porosity were examined. The SS 316 stainless wire mesh with a porosity of 9 pores per inch (PPI) were inserted normal to the flow field with a pitch distance of 5 cm for each shape of wire mesh. The experiments were conducted on test rig with air as a working fluid for turbulent flow regime having Reynolds number ranging from 6,000 to 16,000. Experiments were performed on computerized test rig with heated air flowed in one direction through inner pipe and counter flow cold water flowing through the outer concentric pipe. The circular inner pipe of 40 cm long having 4 cm inner diameter (Di), and 3 mm thick was used for experimentation. The experimental results showed that Nusselt number (Nu) increases with decrease in friction factor (f) with increase in Reynolds number (Re). Also, it is observed that the hexagonal porosity shape of wire mesh insert provides higher material contact and gain more energy absorption from hot air resulted in improvement in heat transfer coefficient as compared to diagonal and square porosity shapes of wire mesh inserts, under similar operating conditions. The friction factor and pressure drop for square porosity shape of wire mesh insert is higher as compared to hexagonal and diagonal porosity shapes of wire mesh inserts respectively. This is due to the fact that square porosity wire mesh provides more obstruction in the flow field compared with hexagonal and diagonal porosity shapes of wire mesh inserts. The hexagonal porosity shape of wire mesh insert provides better option for heat exchange applications.

Taguchi ve ANOVA Analizi Kullanılarak Fotovoltaik Enerji Santrallerinde Dizi Tasarımının Optimizasyonu

Fossil fuels, predominant in fulfilling current energy demands, are implicated in global warming, prompting a global shift towards renewable energy sources. Among these, photovoltaic (PV) solar power plants have garnered significant attention, experiencing a rapid surge in installed power capacity. However, a notable drawback of PV solar power plants is their considerable spatial footprint, emphasizing the pivotal role of efficient space utilization and shading mitigation in their design. Notably, pitch distance, array design, and PV type emerge as critical parameters influencing the performance of these power plants during installation. In the present study, eight distinct PV solar power plant designs were conceptualized, incorporating four different PV array configurations (2P-3P-2L-3L) and two PV types (monofacial-bifacial), each with specified orientations (portrait-landscape). Other parameters were held constant across designs. Leveraging PVsyst software, simulations were conducted for each design, yielding crucial performance metrics, including the annual energy output delivered to the grid (E-grid), performance ratio (PR), and associated CO2 emissions. Subsequently, a Taguchi analysis facilitated optimization based on these results. The outcome of this analysis identified the optimal PV array design as 3D and the optimal PV type as bifacial. Further insight was gained through an ANOVA analysis, revealing the substantial contributions of parameters to overall variability. Specifically, PV type exhibited a significant contribution of 65.27%, while PV array configuration contributed 34.72% to the observed variability in plant performance. These findings not only enhance the understanding of PV power plant design intricacies but also underscore the paramount significance of array design in achieving heightened efficiency and sustainability.

Use of machine learning in predicting heat transfer and entropy generation in a flat plate solar collector with twisted tape turbulator and ferrofluid under the influence of an external uniform magnetic field: A numerical study

The flat-plate solar collector is the most common and widely used model of solar collectors. This model of solar collectors is more popular than other solar collectors due to its easy installation and lower cost. It is possible to further reduce the cost and size of these systems by improving their performance. For this purpose, simultaneous application of external uniform magnetic field (MF), water-Fe3O4 ferrofluid, and twisted tape turbulator along with changing the cross-section of the serpentine absorber tube of a collector is proposed in the present research. The outlet temperature of working fluid, pressure drop of working fluid, the rate of thermal energy transferred to the flowing fluid in the collector along with the entropy production rate in the system due to fluid friction and heat transfer were considered as the performance parameters of the system. The effect of cross-section of absorber tube (circular, square, triangular), Reynolds number (Re = 500, 1000, 1500 and 2000), pitch distance of turbulator (δ = 150 mm, 200 mm and 250 mm), ferrofluid volume fraction (σ = 0, 1 %, 2 % and 4 %) and magnetic field intensity (0, 600, 900 and 1200 Gauss) on these parameters was investigated numerically using the finite volume method. In the investigations conducted in the absence of MF, collectors equipped with circular and triangular absorber tubes showed the best and worst thermal performance, respectively, while the lowest and highest total entropy production rate was associated with collectors equipped with circular and rectangular tubes, respectively. Moreover, the escalation in σ from 0 % to 4 % and under the MF effect showed an increase of 0.14 %, 8.62 %, 0.45 %, and 4.55 % in the outlet temperature, pressure drop, useful heat, and thermal entropy generation rate, respectively. While the frictional entropy generation diminished by 8.73 %. In addition, the intensification of MF intensity from 0 G to 1200 G led to enhance the outlet temperature, useful heat, and pressure drop, by almost 0.0014 %, 3.96 %, and 0.013 %, respectively at three different σ values. While total entropy generation rate reduces by 0.195 % as MF intensity increases from 0 G to 1200G. Meanwhile, the results of neural network modeling were presented as two second-order polynomial functions to predict the total entropy generation rate and useful heat under the MF effects.

Neural network-based regression for heat transfer and fluid flow over in-line cylinder arrays with random pitch distances at low Reynolds number

Finding an arrangement, leading to a higher heat transfer and lower pressure drop, is crucial in the design of heat exchangers. Previous studies have primarily focused on regular arrangements with uniform pitch distances, which lack applicability to general configurations. In this study, we proposed a new procedure of a flow-learned building block (FLBB) to predict heat transfer in an in-line cylinder array with random pitch distances using a neural network-based regression analysis with a systematic data generation process. As a first step, we demonstrated the FLBB’s capability to predict the heat transfer and pressure drop in in-line cylinder arrays with random pitch distances at low Reynolds numbers from 1 to 100 for air ( ). Subsequently, a high-order FLBB approach was proposed to address the spatial interdependency between neighbouring cylinders, particularly in scenarios where vortex shedding occurs in the wake of cylinders at increased Reynolds numbers. The high-order FLBB approach was then shown to successfully describe various flow and temperature patterns using cylinder arrays with random pitch distances. The proposed procedure exhibited remarkable efficiency, requiring only about 1 s. Furthermore, the FLBB was successfully extended to various flow regimes, even encompassing unseen Reynolds numbers from 1 to 100.