Laminar Range Research Articles

Efficacy of jute-glass hybrid laminate composite wrapping under flexural loading

The demand for sustainable engineering materials has catalyzed interest in hybrid composites that combine natural fibers like jute with synthetic fibers such as E-glass. This study investigates the flexural strength of jute/E-glass/epoxy hybrid composite laminates under different stacking sequences, employing the ANOVA method to analyze their mechanical performance. The materials, including jute fabric, E-glass fabric, and epoxy resin, were arranged in various configurations and tested for flexural strength following ASTM D790 standards. The results indicated significant variability, with the GJGJ configuration exhibiting the highest average flexural strength of 71.20 MPa, while the GJG configuration had the lowest at 26.33 MPa. The ANOVA analysis confirmed a statistically significant effect of laminate configuration on flexural strength (F = 6.41, p = 0.004). These findings underscore the critical role of laminate arrangement in enhancing the mechanical properties of hybrid composites. The superior performance of the GJGJ configuration suggests that alternating layers of jute and E-glass fibers can effectively distribute stress and enhance load-bearing capacity. Conversely, suboptimal configurations like GJG demonstrated lower performance, highlighting the importance of strategic fiber arrangement. This research contributes to the development of optimized hybrid composites for various engineering applications, providing valuable insights into the interplay between natural and synthetic fibers within a composite matrix. The study's conclusions support the broader use of hybrid composites in industries such as automotive, construction, and aerospace, where material sustainability and performance are paramount. Future research should explore further optimization of stacking sequences and volume fractions of fibers, as well as investigate other mechanical properties such as tensile and impact strength, to fully realize the potential of hybrid composites in advanced engineering applications

Analysis of the Spanwise Effect behind a Cylindrical Body

The study of the flow around the cylinder is still a focus of research in various aspects. In this case, the flow around an electrically heated cylinder with a diameter Ød=10 mm is investigated at low velocities (mainly in the laminar range). In the literature, the wall temperature Tw is used in many places to characterize such flows. This is usually considered constant, because experimental tests are mainly performed with electrically heated rods of small diameter (max ~2 mm). Since in our case the rod diameter is a multiple of this, the question arises whether the two-dimensional nature of the flow behind the cylinder is preserved. The spanwise effect behind a transversely placed heated cylinder was investigated. The results obtained provide a good basis for designing further measurement options.

Determining Quasi-Static Load Carrying Capacity of Composite Sandwich Rotor Blades for Copter-Type Drones

The development of light composite rotor blades with acceptable load carrying capacity is an essential issue to be dealt with in the design of relatively large copter-type drones. In this paper, a method is established to determine the quasi-static blade load carrying capacity which is vital to drone reliability. The proposed method, which provides a systematic procedure to determine blade load carrying capacity, consists of three parts, namely, a procedure to determine the distributed quasi-static blade aerodynamic load via the Blade Element Momentum (BEM) approach, a finite element-based failure analysis method to identify the actual blade failure mode, and an optimization method to determine the actual blade load carrying capacity. The experimental failure characteristics (failure mode, failure thrust, failure location) of two types of composite sandwich rotor blades with different skin lamination arrangements have been used to verify the accuracy of the theoretical results obtained using the proposed load carrying capacity determination method. The skin lamination arrangement for attaining the optimal blade-specific load carrying capacity and the blade incipient rotational speed for safe drone operation has been determined using the proposed method.

Evaluation of tensile strength and flexural strength of GFRP composites in different types of matrix polymers

Resin selection has a crucial role in determining the properties and performance of GFRP composites; this study aims to investigate the effects of different resin types, specifically epoxy, bisphenol, ripoxy, and polyester, on the mechanical strength of GFRP composites.The composites were fabricated using the conventional method of hand lay-up technique with a fiber to matrix ratio of 60:40 wt%. The glass fibre laminate arrangement consists of 4 layers, two layers of Woven Roving Mat (WRM) fibres (0/90) and 2 layers on the outer side of the Chopped Strand Mat (CSM). The composite specimens were molded using the ASTM D-838 tensile test standard and ASTM D-790 for the bending test.The research results found that the maximum tensile strength was obtained by GFRP composite with ripoxy matrix type of 181.6 MPa, strain of 0.028%, and flexural strength of 1387 MPa. Composites using polyester matrices can generally be classified as splitting in multiple areas where failure occurs in various areas, but the composite has very high strength.Material experiments conducted on a scientific laboratory scale may not fully reflect the behaviour of composites in actual conditions. Furthermore, aspects such as environmental influences, sustained stresses, or fatigue effects may need to be considered in further research. This evaluation also does not consider the effects of long-term exposures or ageing on the mechanical properties of GFRP composites. Investigating the behaviour of materials over long periods can provide important insights into their durability and reliability in practical applications.In GFRP composites, the application of resin to the fibres is critical. The performance and mechanical characteristics of GFRP composites are largely determined by the polymer matrix. Composites with epoxy, polyester, or bisphenol matrices can be compared to composites with the most equivalent tensile strength values, but composites with ripoxy matrices can be suggested. However, the GFRP composite with bisphenol matrix has an excellent bending strength value. As a result, numerous applications exist for implementing matrix selection in producing GFRP composites.The reliability of the tensile properties of GFRP composites was obtained using the ripoxy matrix type. Furthermore, the reliability of the flexural properties of the composites was obtained using the bisphenol matrix type.

Numerical simulation of the laminar boundary layer flow over a flat plate

Understanding the dynamic and thermal characteristics of the boundary layer (BL) flows is an essential step toward the best design and operational conditions for many engineering devices. Flow characteristics within the boundary layer are governed by two forces that are in a mutual race to dominate the flow, the viscous and inertial forces. The state of the flow is determined by the relative domination of these two forces inside the boundary layer zone. Theoretical solutions for many BL flow types existed since the beginning of the 20th century. Theoretical solutions are strictly possible for simple boundary layer flow configurations within the laminar range and before flow separation occurs. For practical situations where boundary layer flow problems are prescribed with complex flow configurations, CFD techniques represent the most suitable approach to tackle such types of flows. In this study, the laminar boundary layer flow over a flat plate has been solved numerically leading to a detailed analysis of the boundary layer flow with accuracy comparable to that of the theoretical solution

Thermo-fluidic analysis of microchannel heat sink with inline/staggered square/elliptical fins

The present study reports the thermo-fluidic behavior of a microchannel heat sink employed over a heat source dissipating a heat flux of 50 W/cm2. The microchannel heat sink is embedded with elliptical and square fins varied from 11 × 3 (11 fins per row with a total of 3 rows) to 79 × 3 fins and 100 μm to 300 μm height to obtain the optimum configuration for maximum heat transfer and minimum frictional loss. Fluid flow is considered in the laminar range of Re varying from 100 to 400. The problem is solved numerically using a Finite Volume Method based multigrid solver of ANSYS Fluent. The aim of the present study is to investigate the shape effect of square fin (α = 0), square fin (α = 45) and elliptical fins on the heat transfer from the heater surface and frictional loss. This is achieved by keeping the correctional area and the surface the same for all types of fins. It is found that the heater surface temperature monotonously decreases with the number of fins for a fin height more than 200 μm. When different fin shapes are compared, no remarkable difference in the heater surface temperature is observed; however, elliptical fins are marginally more effective for a greater number of fins than the square fin with α = 0 followed by α = 45. Increasing the fin height results in augmenting the heat transfer for all cases. When different arrangements are compared, staggered fins result in slightly better heat transfer than the inline fins except 11 × 3 and 79 × 3 fins. As far as friction factor is concerned, elliptical fins with staggered arrangement provide the least frictional resistance.

Lattice Boltzmann Computation of Steady Cross-Flow Across a Rectangular Obstacle with Different Aspect Ratio: Effect of Blockage Ratio

This work presents a two dimensional lattice Boltzmann analysis of steady and cross-flow of New tonian fluid across a built-in rectangular cylinder. In particular, the effects of the blockage ratio and aspect ratio of rectangular cylinder (width/height) on the momentum characteristics have been explored for range of flow governing parameters such as, blockage ratio (β = 1/8, 1/12, 1/16), aspect ratio of rectangular cylinder (1 ≤ a_r ≤ 6) at constant Reynolds number of Re = 40 corresponding to the laminar range. The physical insight of system is gained by evaluation of stream-function, vorticity and pressure coefficient variation, etc. Further, the engineering gross parameter, such as drag coefficient is determined for possible use in engineering design purpose. It is observed that the increase in blockage ratio drag coefficient values decreases and drag values show proportional variation with aspect ratio. Finally, a closure relationship is developed between drag coefficient, blockage ratio and aspect ratio of rectangular cylinder for possible use in engineering/scientific practices

Heat Transfer and Entropy Generation in a Lithium-Ion Battery Pack Against Battery Spacing and Discharge Rate

Abstract Three-dimensional continuity, momentum, and energy equations have been solved in a battery pack of a unit module with 3 × 3 × 3 and 4 × 4 × 4 Li-ion cells to obtain the flow field and temperature distribution around the batteries. The battery spacing to hydraulic diameter ratio in x, y, and z directions have been varied in a wide range from 0.04458 to 0.08172, 0.00833 to 0.07133, and 0.007496 to 0.08052 for 4 × 4 × 4 cells, and 0.06 to 0.11, 0.0111 to 0.09649, 0.01 to 0.11 for 3 × 3 × 3 to obtain the optimum configuration for maximum heat transfer and minimum entropy generation. Air is pumped through the battery pack as a transport medium for heat transfer with Reynolds number (Re) varying in the laminar range from 400 to 2000. The results are plotted in terms of the average surface Nu over the battery surface and average volumetric temperature of the battery and air. It is found that the temperature of the battery pack remains almost constant against Sx. However, a significant rise in battery temperature is observed when we increase Sy. The scenario becomes different when spacing is varied in the z-direction. An optimum spacing for the minimum temperature of the battery pack is obtained at Sz/Dh = 0.03. The temperature variation trend is almost identical in 3 × 3 × 3 and 4 × 4 × 4 cells; however, the absolute temperature inside the pack is lower in 3 × 3 × 3 cells. In each case, the maximum temperature is seen on the batteries located at the top and bottom corners of the outlet. Among all the cases, the maximum temperature of 355 K has been found in 4 × 4 × 4 cells with a 3.6C discharge rate at Sy/Dh of 0.07133. Different discharging rates (1C, 2C, 3.6C, and 4C) have been considered to generate different amounts of heat inside the battery. However, it is numerically and theoretically proved that Nu and the nondimensional volumetric average temperature inside the pack are independent of the heat generation rate inside the battery pack.

Design of a packed bed chemical looping (unmixed) combustion reactor for the application of heating liquid: A theoretical study

AbstractA packed bed reactor (PBR)‐based chemical looping combustion (CLC), also referred to as unmixed combustion (UMC), was reported as an alternative to fire in the literature. In this process, the oxygen carriers undergo oxidation and reduction reactions in alternate cycles using air and fuel as the reactive gases, respectively. The energy generated in these reactions can radially be transferred for applications like heating air which was successfully demonstrated. The results showed that 85–95% of the generated energy can radially be transferred while maintaining sustained combustion in the bed (at temperatures between 723 and 1173 K). While extending its application for heating liquids like water, it was found in the modeling and simulation study that the existing design resulted in quenching of the bed below 773 K in the oxidation cycle and achieving sustained combustion was not possible for all practical ranges of operating parameters. Hence it was decided to modify the existing system by increasing the volume ratio of the annular bed to the liquid section. Theoretical estimations revealed that increasing this ratio by four times or higher can result in maintaining sustained combustion conditions in the bed while having continuous radial heat transfer to the water flowing in the laminar range. The general guidelines for designing a UMC‐based liquid heating system were then prepared and used to propose a new design for water heating. The modeling and simulation studies for this proposed design also indicated that it is a feasible design. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Improvement of Plate-Fin Heat Exchanger Performance with Assistance of Various Types of Vortex Generator

A 3-dimensional incompressible laminar flow and heat-transfer in a plate-fin heat exchanger (PFHE) where investigated numerically in this article. The influence of mounting a longitudinal vortex generator (LVG) on the offset rectangular-triangular fin (ORT) in the PFHE, on thermal and hydro-dynamic fields are presented. The novelty of this study is by attaching a LVG to an offset strip fin (OSF) surface. The cases of study for the PFHE are established, by using a built-in rectangular winglet pair type RWP longitudinal vortex generator carried out and fitted on this fin to improve the convective heat transfer of the (ORT) fin while minimizing pressure loss. The upper and lower plates are exposed to constant heat flux and the working fluid is air where chosen under a laminar range of RE (600 to 1400). The laminar flow and heat-transfer are governed by continuity, momentum and energy equations. ANSYS FLUENT (2021 R1) is used to get the numerical results, based on the finite volume method. The performance of the VG is assessed for an optimum winglet attack angle (45°), as well as by modifying the geometrical size parameters, namely the height and placement (L) of the RWP LVG. The result shows that the Nusselt number reaches its optimum enhancement values by using a common flow up CFU built-in rectangular winglet pair type RWP VG with a height and entrance length of (h=1.25mm, L=0.5mm), by 22.23% as compared with base case configuration (ORT). Finally, a two more LVG are tested with the optimum conditions of the RWP, which they are a delta winglet pair (DWP) and trapezoidal winglet pair (TWP). In addition, the temperature fields for the primary and secondary flows were shown in contour and streamline diagrams

Buckling in rectangular hybrid composite plates with angled groove-shaped cut-outs

Abstract In this paper, eight-layer composite laminates were produced using twill and plain woven glass and carbon laminate fibers as a reinforcement element and as a matrix with epoxy resin. All laminates having the layup of [(0°/90°)2]s but the hybrid laminate arrangement varies between the number of woven glass and carbon laminates. The buckling behaviour of woven composite laminates used for typical of the aerospace industry is investigated. Un-grooved and grooved with centered elliptical groove angles with 0°, 15°, 30°, 45°, 60°, 75° and 90° specimens were subjected to buckling tests. It was investigated how the woven type, laminate designation, and groove angles affect the buckling behaviour. Cut-out causes to decrease of buckling load of composite plates. It is understood that the buckling load increased with regard to the increase groove angle (from 0° to 90°) of the composite plates. As the laminate designation changed, the buckling load also changed significantly. The buckling load of composite plates is highly influenced by its weave type. As a fiber, it has been determined that the buckling behaviour of carbon fiber is better than glass fiber. In addition, it was concluded that the twill weave type is generally better than the plain weave type.

Characterization of the Liquid–Lubricant Interface in a Dovetail Cavity for a Viscous Laminar Flow

Lubricant-infused surfaces (LISs) have application in diverse fields based on their liquid-repellent properties. In bulk flow, LISs, however, are susceptible to drainage failure caused by external shear imposed at the liquid–lubricant interface. In this study, the shear-flow-induced lubricant depletion in a dovetail-shaped cavity microchannel has been numerically examined. Lubricant is exposed to five external liquids with different viscosities (μr = 0.2–1) in the laminar range (100 ≤ Re ≤ 1000). Temporal variations in the lubricant depletion from the microchannel and cavities were observed with time. Meniscus shapes were characterized for flows at different viscosity ratios. The results show that when the lubricant is kept fixed, a less viscous external liquid aids in better lubricant retention. Due to the shear imparted, three stable and two failure meniscus shapes have been distinguished. The results are further supported by vortex formation within the cavity and interface velocities contributing to meniscus shapes based on the magnitude of external shear. Additionally, it was evident that, as the viscosity ratio was reduced, the effect of the cavity opening was no longer dependent on the flow rate. It was envisaged that the results will help in the design of a robust LIS system.

Augmentation of Plate-Fin Heat Exchanger Performance with Support of Various Types of Fin Configurations

A plate fin heat exchanger PFHE is a form of compact heat exchanger CHE containing of a block of alternating layers of fins and flat separators known as parting sheets. In this paper, 3-dimensional incompressible laminar flow and heat transfer in a (PFHE) has been investigated numerically. The influences using different fin configurations and the effect of the offset of these fins, on thermal and hydro-dynamic fields are presented. The cases of study for the PFHE are established, by using the fins with different configurations (plain rectangular (PR) and it's offset (OR), plain triangular (PT) and it's offset (OT) which is a novel shape, and a novel combination of a two fin shapes, between rectangular and triangular (ORT)). The upper and lower plates are exposed to a constant heat flux and the working fluid is air where chosen under a laminar range of (Re) number (600 to 1400). The laminar flow and heat transfer is governed by continuity, momentum and energy equations. ANSYS FLUENT (2021 R1) is used to get the numerical results, based on finite volume method. One of the most utilized fins for a PFHE is the offset fin arrangement due to its higher heat change amount, adjustable structure, and enhances flow turbulence and heat transfer coefficient by interrupting the thermal boundary layer. The obtained results of using of the offset configuration increases the Nusselt number by 20.32% and 17.82% for OSF rectangular and OSF triangular, respectively as compared with the with plain configurations, as a result, a significant heat transfer enhancement is observed. And significant increase in the friction-factor is found to be 79.8% and 48.7% for OT and ORT, as compared with the PT. It can be observed that use of the OSF configuration leads to greater f-factor for triangular configuration values. In addition, the temperature fields for the primary and secondary flows were showed in a contour diagram.

Thermal and exergy analysis of Pin-finned heatsinks for nanofluid cooled high concentrated photovoltaic thermal (HCPV/T) hybrid systems

• Cooling performance of HCPV/T is systematically investigated. • Different shaped pin-finned heat sinks (inline and staggered) are examined. • Thermal performance is determined for MWCNT nanofluids. • Exergy efficiencies of pin-fin heat sinks in HCPV/T are evaluated. • 2% MWCNT nanoparticle concentration is found to be the optimum. Cooling of High Concentrated Photovoltaic (HCPV) cells is a major concern among researchers due to higher heat generation in the cells from highly concentrated solar radiation. In the present investigation, a numerical study of the High Concentrated Photovoltaic Thermal (HCPV/T) system is conducted for the combined effect of nanofluids and pin-finned heatsinks on the cooling performance. The investigation is carried out for AZUR SPACE solar cell (Model: 3C44C) for 1000 Concentration Ratio (CR) and the Reynolds number ( Re ) varies within the laminar range (600 ≤ R e ≤ 2200). Different shapes of pin-fins and their orientations are systematically investigated for the effect of Multi-walled Carbon Nanotube (MWCNT) nanoparticles in a base fluid. The results show a significant reduction in the temperature (up to 18K) of the solar cells for the MWCNT nanofluid compared to its base fluid counterpart. A higher heat transfer characteristics (Nusselt numbers) and lower average temperature of top surface of HCPV cells are found to occur for the staggered arrangements of pin-fins. It is also noticed that the volume concentration of MWCNT in water affects heat transfer characteristics and reduction in temperature takes place up to the volume concentration of 2%. About 1.3% reduction in temperature is predicted for adding MWCNT nanoparticle concentration from 0.5% to 2%. However, in terms of exergy efficiency, maximum overall exergy (about 67% for water flow rate of 0.00167 kg/s) is found for square pin-fins with inline arrangements. The average increase in Nusselt number from inline to staggered arrangement are around 11%, 74%, and 22% respectively for circular, square and triangular fins. The maximum electrical efficiency reaches to 42.2% for both 2% and 4% MWCNT with staggered circular pin-fins for a mass flow rate of 0.0058kg/s. Finally, it appears that a combination of nanofluids and pin-finned heatsinks gives a better cooling rate in the HCPV/T system and could be a promising alternative along with other cooling techniques.

Investigation of an electrolysis system with boron-doped diamond anode and gas diffusion cathode to remove water micropollutants.

Using electrolysis systems to degrade organics in wastewater encourages this technique to remove micropollutants (MPs) in different types of water. In this work, a cell consisting of an anode as a boron-doped diamond (BDD) electrode combined with a gas diffusion (GDE) cathode without a separator showed that MPs degradation can be effectively achieved. Investigating different operating parameters, it was stated that applying a low current density (2 mA/cm2) and setting the Reynolds number of the electrolyte flow through the cell at the laminar range raised the treatment time by 3-fold at the same energy demand. This arrangement increased the MPs removal. Some substances like diclofenac were removed up to 84% at a longer treatment time of 180 min coupled with an increase in energy demand. The results at the mentioned parameters indicated an adequate generation rate of radicals needed to remove MPs and the oxidation reactions were promoted. The results show high potential to the investigated electrolysis system in removing MPs in wastewater under considering the need for further reduction of the energy demand.

Natural Convection From an Isothermally Heated Hollow Vertical Cylinder Submerged in Quiescent Power-Law Fluids

Abstract An attempt has been made to study the natural convection around a hollow vertical cylinder numerically which is suspended in motionless power-law fluids in the laminar range. The influence of various non-dimensional pertinent parameters, such as Grashof number (10 ≤ Gr ≤ 105), Prandtl number (0.71 ≤ Pr ≤ 100), and power-law index (0.2 ≤ n ≤ 1.8) on thermofluid characteristics around the hollow cylinder, is predicted computationally. Simulations are performed by varying the cylindrical aspect ratio (L/D) over the range of 1 ≤ L/D ≤ 20. It is reported that the average Nusselt number appreciably grows with the rise of Gr or/and Pr for a constant L/D. Moreover, the rate of rising of Nusselt number (Nu) with Gr or/and Pr strongly depends upon the power-law index (n); i.e., Nu finds a stronger dependence on Gr than that of Pr with a lower value of n (shear-thinning fluids, (n < 1)) and a completely different pattern has been noticed in shear-thickening fluids (n > 1). Furthermore, the average Nu on the outer wall (Nuouter) grows approximately in a linear way with an increase in aspect ratio for a particular Gr, Pr, and n. In contrast, Nuinner drops drastically and almost attains the asymptotic trend at a greater value of aspect ratio for lower Gr or/and Pr. The decreasing pattern of Nuinner is found to be remarkably steep for n < 1 (shear-thinning fluids) in comparison to n > 1 (shear-thickening fluids). Correlations are developed for Nuouter and Nuinner in terms of Gr, Pr, n, and L/D, which operate extremely well within ± 6% of the computational data.

Three-dimensionality in the flow of an elastically mounted circular cylinder with two-degree-of-freedom vortex-induced-vibrations

The study numerically investigates the three-dimensionality in the flow and two-degree-of-freedom (2DOF) vortex-induced-vibrations (VIV) characteristics of an elastically mounted circular cylinder. The cylinder is allowed to vibrate in both streamwise and transverse directions. A low value of mass-ratio (m*=2.546) with the zero-damping coefficient (ζ=0) is taken for the simulations. The primary aim is to understand the vortex shedding behind the cylinder and the transition characteristics of the wake-flow from two-dimensional (2D) to three-dimensional (3D). The Reynolds number (Re) is varied from 150 (fully 2D flow) to 1000 (fully 3D flow), which lies inside the laminar range. The reduced velocity (Ur) is varied 2≤Ur≤17, which covers all three major VIV branches [initial branch (IB), upper branch (UB), and the lower branch (LB)]. The oscillating cylinder sweeps the figure-eight trajectory. Two branches (IB, LB) and three branches (IB, UB, LB) amplitude responses are obtained for the low and high Re values, respectively. The wake behind the cylinder with 2DOF VIV undergoes the mode-C transition of 2D to 3D flow as opposed to the direct mode-B transition observed for transverse only VIV in the literature. The critical Re range of the 2D to 3D transition for the 2DOF VIV cylinder at a reduced velocity of 6 is around 250, less than the 1DOF VIV. Also, this range varies with the variation in m* and the streamwise to transverse oscillation frequency ratio (f*). A λz−Re map (where λz represents the spanwise wavelength of the streamwise vortices) is proposed for the 2DOF VIV, highlighting different modes of transition obtained for combinations of f* and Re.

Natural-Convection Heat Transfer from Upward/Downward/Sideward Converged or Parallel Finned Hemispheres

Natural-convection heat transfer from a finned hemisphere is solved in the laminar range of Rayleigh number ( to ) to predict the flowfield and the temperature distribution around it. Two different types of fins, namely, converged and parallel fins, have been employed with fin height varied from to and fin number from 8 to 40. The hemisphere is placed either upward, downward, or sideward to observe the orientation effect on the heat transfer. It is found that Nusselt number for the downward and sideward finned hemisphere is less than that of the upward finned hemisphere for greater than 20. The hemisphere with parallel fins results in greater Nusselt number than converged fins at any Rayleigh number for upward and downward hemispheres. The situation reverses for the downward hemisphere at a high of . For a sideward hemisphere, the Nusselt number for converged fins is more compared to parallel fins. The hemisphere with converged fins is found to be more effective in heat transfer because such fins generate more surface area for heat transfer. Eventually, the correlations for average surface Nusselt number against various input pertinent parameters have been proposed for different orientations of the hemisphere.

Parametric study of natural convection showing effects of geometry, number and orientation of fins on a finned tube system: A numerical approach

The present study provides a thorough numerical analysis of natural convection heat transfer from a horizontal cylinder with external longitudinal fins. The Three-dimensional(3D) forms of Continuity, Navier-stokes, and the energy equations have been solved to understand the flow field and temperature distribution using the Ansys Fluent software. The purpose of the study is to investigate the effects of fin length Lf, fin thickness (t), number of fins (N) and material of fin (Aluminum & Steel) on the parameters namely, the heat transfer rate from the inner isothermal wall and effectiveness (Q*)of the system for a constant Rayleigh number in the laminar range (Ra ≤ 106). Additionally, the effect of two different orientations (A&B) of fins has been discussed. Orientation-A consists of fins starting from horizontal plane placed at equal angular spacing subsequently, whereas the fins in orientation-B originate from the vertical plane followed with equal angular spacing. Non-dimensional fin length (L*) is being varied from 0.222 to 2, non-dimensional fin thickness (t*) as 0.022 ~0.044 and the number of fins (N) between 6~24. It is observed that for a fixed number of fins there exists an optimum fin length and for a fixed fin length there exists an optimum fin thickness & an optimum number of fins. For a fixed number of fins there exist an optimum fin length and maximum effectiveness, the maximum possible effectiveness for the taken fin-tube system is 4.34 for 12 fins. The maximum effectiveness reported in the current study was 1.86 for L*=0.444, t*=0.022 and N=12. Furthermore, the optimum length for N=12 came out to be L*=1.8.

Numerical and Experimental Study of a Novel Additively Manufactured Metal-Polymer Composite Heat-Exchanger for Liquid Cooling Electronics

In order to meet increasing power-dissipation requirements of the electronics industry, compact, low-cost, and lightweight heat exchangers (HXs) are desired. With proper design, materials, and manufacture, polymer composite heat exchangers could meet these requirements. This paper presents a novel crossflow air-to-water, low-cost, and lightweight metal-polymer composite HX. This HX, which is entirely additively manufactured, utilizes a novel cross-media approach that provides direct heat exchange between air and liquid sides by using connecting fins. A robust numerical model was developed, which includes the dimensional effects of additive manufacturing. The study consists of a simplified 3D CFD model based on ellipsoidal-shaped staggered tube banks for the laminar range. It then uses an analytical approach to compute entire HX performance. The model is validated experimentally within 8% for thermal performance, 12% for air-side impedance, and 18% for water-side impedance. Finally, HX is compared with a conventional CPU radiator and performs within 10% of the conventional unit for reasonable flow rates and pressure-drop ranges. Moreover, HX also provides added design and cost advantages over the conventional unit, which makes the HX a potential candidate for electronic cooling applications.