Tube Shape Research Articles

Enhancing heat transfer in the heat exchange medium of energy piles

As systems for utilizing geothermal energy, energy piles have been widely employed in many engineering applications, and they offer various advantages. A significant amount of research has been devoted toward developing methods to enhance the heat exchange efficiency of these systems, including studies on the shape of the heat exchange tube and the shape and spacing of the energy piles. After around four decades of research and development, existing methods for improving the heat exchange efficiency have become relatively mature, thus hindering further improvements. Therefore, it is essential to develop an alternative approach for enhancing the heat transfer and improving the heat exchange efficiency of these systems. To this end, this paper first summarizes the conventional heat transfer model and then elaborates on the selection of the concrete pile material as the heat transfer medium. In this study, samples of graphite concrete and silicon carbide (SiC) concrete were prepared. Subsequently, several tests on the heat transfer behaviors and mechanical performances of the samples were conducted, in order to determine the physical and mechanical properties of the modified concrete. The results showed that, at the same ambient temperature, when the graphite content exceeded 15%, the heat transfer coefficient increased, leading to a significant improvement in heat transfer. However, the compressive strength decreased noticeably. With an increase in the SiC content, the thermal conductivity of the concrete gradually increased, while the compressive strength of the concrete with SiC increased considerably. The results proved that modifying the concrete used in energy piles is a feasible method for improving heat transfer.

Fabrication and Characterization of CdO Gas Sensor with Tube Shape

The based semiconductor-metal oxide gas 3D-detector of cadmium oxide has been fabricated from cadmium chloride salt upon a glass substrate via the technique of spray pyrolysis with a thickness around (0.5 ± 0.01 μm) utilizing precursors in form of water soluble at a flat glass substrate and a tube hollow design. Three different dimensions were used at temperature 450oC±5, in 0.1 and 0.2 M concentration, and their gas sensing characteristics toward the (CO) and (NO) gases at various concentrations (50, 100, and 500 ppmv) in the air were studied at the room temperature which are related to oil industry. Different inspection distances (0, 1 and 5 m) were carried out. Furthermore, structural and morphology properties were inspected via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results manifested that the composition of the formative oxide CdO is related to the tested oxidation gases sensitivity. And, the installation of hollow design is best from flat to capture the gas molecules.

Twisted tape variable wavelength effect on nanofluid flow and heat transfer inside elliptical shape tube

In this investigation, fluid flow and heat transfer in a tube having circular and elliptical shapes are studied numerically. Using twisted tapes with constant and variable wavelengths along the flow on the flow field and heat transfer is investigated. The governing equations are solved with the finite volume method. The accuracy of numerical results in the turbulent flow simulation is assessed by validating and comparing the numerical results with the available experimental data. MWCNT/water nanofluid was used to enhance the heat transfer. The influence of volume fraction of nanoparticles on flow behavior and heat transfer in the presence of the twisted tape was studied. The tube shape (circular and elliptical shape with aspect ratios of 0.6 and 0.8), Reynolds number (from 4000 to 16,000), twisted tape wavelength (0.1 and 0.2), and the nanoparticles volume fraction (from 0.005 to 0.03%) are the independent parameters. The obtained numerical results showed that modifying the tube’s shape to elliptical and increasing the number of tape twists increase the heat transfer and friction coefficient. According to the results, in the flow with the maximum Reynolds number (16,000) and minimum tape wavelength, heat transfer was enhanced by 21%, while the pressure drop was augmented by 1.4 times. Investigation of the thermo-fluidic performance of the nanofluid revealed that for flows inside tubes with elliptical shape, the use of nanofluid is more desirable than pure water, and nanofluid is recommended when there is a twisted tape in the flow path. Streamlines at Reynolds number of 16,000 inside elliptical shape for λ2-3 = 0.1–0.2 m with variable wavelength

Enhancing the output performance of fluid‐based triboelectric nanogenerator by using poly(vinylidene fluoride‐co‐hexafluoropropylene)/ionic liquid nanoporous membrane

Over the past few years, triboelectric nanogenerators (TENGs) have emerged as promising devices for energy harvesting and self-powered sensing owing to their miniaturized structural design, lack of material limitation, high stability, and eco-friendly nature. In this study, the membrane consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and ionic liquid (PIL) is fabricated as triboelectric material, namely PIL membrane. To further improve the hydrophobicity of the membrane and the output performance of the TENG, different PIL membranes are prepared using various IL concentrations and their structures are modified using the evaporation phase inversion technique. The PIL membranes with nanoporous structures and strong hydrophobicity are synthesized by blade coating and bent to generate circular tube shapes for use in PIL-TENG cells. Therefore, the PIL-TENG has a high output performance owing to the availability of more ions through the establishment of an electrical double layer and an increase in electronegativity properties by doping with more fluoride atoms. Under optimal conditions, a nanoporous PIL-TENG of 10 wt.% ionic liquid exhibited the maximum peak-to-peak with an output voltage of 16.95 V and current of 2.56 μA. Especially, the instantaneous peak power density of the PIL-TENG reached the highest value of 26.1 mW/m2, which was 212% higher than that of the pristine PVDF-HFP TENG (P-TENG). In this manner, a new material for the triboelectric layer is presented to effectively improve the output performance, stability, and durability of TENGs, which are promising for use in practical applications related to harvesting hydrokinetic energy, self-powered sensors, and other applications.

Усовершенствованный резонатор Гельмгольца

The three-dimensional acoustic finite element method is used to predict the transmission loss of the Helmholtz resonance muffler. The results are in good agreement with the experimental results, indicating the applicability and accuracy of the numerical method used in this paper. On the one hand, in order to reduce the resonance frequency without changing the shape of the resonator, the connecting tube is extended to the inside of the resonator, and the influence of the extension length and the cross section shape of the extension tube on the acoustic characteristics of the resonator is discussed in detail. On the other hand, in order to broaden the muffled frequency band of the traditional Helmholtz resonators, the resonators are combined in series and parallel, and the influence of the combined structure on the acoustic characteristics is discussed in detail.

Numerical simulation of filling and evacuating process of impurity gas in target capsule of inertial confinement fusion

Cryogenic target is one of the key components of inertial confinement fusion. The removal degree and efficiency of impurity gas in cryogenic target are of great significance to the on-line preparation of ice layer for cryogenic target fuel. According to the design requirements of cryogenic target physics for impurity content in ice layer, the influence factors of upper limit of partial pressure are analyzed, based on the derivation of the calculation formula of maximum allowable partial pressure of impurity gas in the target. Then the flow field of air and hydrogen in microchannels is investigated, and the filling and evacuation model of gas flow in a microscaled filling tube is established. The dynamic simulations of microtubules with different lengths and diameters are carried out. The results show that the microtubules with a length of 5 mm could save 80% of the time compared with the microtubules of 50 mm in length when the microtubule is 5 μm in diameter. At the same time, the total flow washing time decreases by 46% when the diameter of 2 μm is doubled under the condition of 20-mm-long microtubule. Considering the requirements for efficiency and fusion stability, four kinds of tubes are proposed and simulated. The results indicate that the conical transition tube has a strong flow capacity and high flow evacuation efficiency, and is suitable for use as a filling microtubule. On the basis of the best tube shape, the comparison between the two processes under different intermediate pressures is carried out with the time and number of filling and evacuating serving as evaluation criterion. Ultimately, the intermediate pressure of 52000 Pa is selected, the total number of evacuation is 10 and the time is 758 s. Finally, the effect of temperature on the evacuation efficiency is studied in a temperature range of 113 K－293 K in steps of 60 K. The results show that the total time of filling and evacuation will be reduced by 15% on the basis of normal temperature when the temperature is reduced by 60 K, which proves the feasibility of evacuation at low temperature in practical operation.

Cells into tubes: Molecular and physical principles underlying lumen formation in tubular organs.

Tubular networks, such as the vascular and respiratory systems, transport liquids and gases in multicellular organisms. The basic units of these organs are tubes formed by single or multiple cells enclosing a luminal cavity. The formation and maintenance of correctly sized and shaped lumina are fundamental steps in organogenesis and are essential for organismal homeostasis. Therefore, understanding how cells generate, shape and maintain lumina is crucial for understanding normal organogenesis as well as the basis of pathological conditions. Lumen formation involves polarized membrane trafficking, cytoskeletal dynamics, and the influence of intracellular as well as extracellular mechanical forces, such as cortical tension, luminal pressure or blood flow. Various tissue culture and in vivo model systems, ranging from MDCK cell spheroids to tubular organs in worms, flies, fish, and mice, have provided many insights into the molecular and cellular mechanisms underlying lumenogenesis and revealed key factors that regulate the size and shape of cellular tubes. Moreover, the development of new experimental and imaging approaches enabled quantitative analyses of intracellular dynamics and allowed to assess the roles of cellular and tissue mechanics during tubulogenesis. However, how intracellular processes are coordinated and regulated across scales of biological organization to generate properly sized and shaped tubes is only beginning to be understood. Here, we review recent insights into the molecular, cellular and physical mechanisms underlying lumen formation during organogenesis. We discuss how these mechanisms control lumen formation in various model systems, with a special focus on the morphogenesis of tubular organs in Drosophila.

Crashworthiness Analysis of a Thin-Walled Structure in the Frontal Part of Automotive Chassis

With increasing road accidents, researchers found a need to reduce the impact which gets transferred to the driver and passengers during a collision. Chassis is the main rigid component which transmits the impact or jerk to the entire vehicle. So, the changes can be done in the frontal head tube shape in order to achieve maximum energy absorption. The objective of this article is to produce a thin-walled impact absorption structure. The unique strength absorption, the maximum crushing force, all through the frontal impact are the primary dimensional parameters of the performance. Explicit dynamics feature of Ansys can be used and the results of Peak Force (PF) and Specific Energy Absorption (SEA) can be acquired virtually. Based on the results, the shape with the highest amount of SEA can be concluded as the best shape so that it can be used to absorb the maximum energy while collision of the vehicle takes place. The results show an increment of 30% in SEA.

Effects of Rotational Feed at Constant Angles on Forged Shape in Mandrel-Less Incremental Forging of Thick Circular Tube

This paper focuses on the formability of mandrel-less incremental forging to produce tubes with variable wall thickness. Tubes with variable wall thickness have advantages in weight saving and resource saving; therefore, their application to industrial parts such as automotive shafts and railway axles is proposed. Conventional forming technologies, for example, radial forging and drawing, require special tools for each tube shape. It is effective to reduce the necessity of special tools to promote tailor-made production by mandrel-less incremental forging. To produce tubes of specified shape and quality by mandrel-less incremental forging, an understanding of the effects of forging conditions on forming characteristics is necessary. As a first step in this research, the effects of rotational feed at a constant angle, which is a simple condition, on forged shape were examined by forging experiments and finite element simulation. The forming characteristics that the forged shape depends on the geometrical contact angle between the workpiece and the die and on the total rotational angle were clarified.

Cushioning energy absorption of regular polygonal paper corrugation tubes under axial drop impact

Abstract The paper corrugation tube is an attractive and innovative mode of cushioning protection and energy absorption for the general protection and packaging technology of military and civil products. The aims of this paper focus on the dynamic compression characteristics of four kinds of regular polygonal paper corrugation tubes under the conditions of axial drop impacts, and the influence rules of structural parameters and load parameters on the dynamic cushioning energy absorption. The results show that, the tube direction has a crucial effect on the deformation mode of the paper corrugation tubes, the deformation of X-direction paper corrugation tubes has a stable accordion mode, but that of Y-direction paper corrugation tubes is a mixture of steady progressive buckling and other non-ideal modes. The X-direction paper corrugation tubes have lower peak stress, stable and controllable deformation mode with multiple folds, and higher total energy absorption, unit area energy absorption, specific energy absorption and stroke efficiency than the Y-direction paper corrugation tubes. Moreover, the change of cross-section shape of X-direction paper corrugation tubes has no obvious influence on the total energy absorption, while the total energy absorption of Y-direction paper corrugation tube obviously rises with the increase of the number of cross-section edges of the tubes, but the unit area energy absorption, specific energy absorption and stroke efficiency decrease with the increase of the number of cross-section edges of the tubes. Moreover, the increase of the number of cross-section edges of the tubes made the total energy absorption of Y-direction tubes rise, while the total energy absorption of X-direction tubes has no obvious change. But the unit area energy absorption, specific energy absorption and stroke efficiency decrease with the increase of the number of cross-section edges of the tubes. Furthermore, the tube length, impact block mass and impact energy have also important influence on the cushioning energy absorption of the paper corrugation tubes under axial drop impact.

Cavity receivers in solar dish collectors: A geometric overview

Many studies, as numerical and experimental, regarding the applications of solar dish concentrators have been performed. Most researchers focused on the maximum thermal efficiency, the minimum heat loss, and their relations to the solar receiver geometries. This paper presents and discusses the previous studies investigating different cavity receiver geometries and their optimization methods with parabolic dish collectors. More specifically, cylindrical, hemispherical, conical, and flat sides cavity receivers are investigated in this manuscript. For an inlet operating temperature of 200 °C, the conical cavity shape has shown a thermal efficiency of around 70%, exergy efficiency of 30%, and optical efficiency of around 87%. The working fluid temperature is often around 650 °C–750 °C in the solar dish collectors. Due to high working temperature and cavity shape, heat losses such as radiation, conduction, and convection losses are highlighted that could provide adverse effects upon the system thermal efficiency. Besides, the diameter aspect ratio, the cavity inclination angle, type of tube, and the tube shape can be impressive on the cavity heat losses value. Therefore, the optimized geometry of the cavity receiver is a vital subject. Based on the analyzed issues, some suggestions and concluding remarks are presented.

Numerical investigation and design optimization of a novel polymer heat exchanger with ogive sinusoidal wavy tube

In this paper, a novel polymer bare-tube heat exchanger (BTHX) with an ogive tube shape and a sinusoidal wavy channel is proposed and investigated for the liquid-to-gas application. The thermal-hydraulic performance of the proposed polymer BTHX is calculated using a validated computational fluid dynamics (CFD) simulation model, and the performance is optimized by setting nine independent design variables. A selective-series CFD method with an approximation-assisted optimization technique is developed for the multi-objective optimization to reduce the computational time. As a result, the thermal-hydraulic performance of the optimized novel polymer BTHX shows 91.5% and 134.9% of that of the target aluminum louvered-fin micro-channel heat exchanger (MCHX), respectively. This is mainly due to the improved air-side heat transfer coefficient of the proposed polymer BTHX by 70.2% compared to the target aluminum MCHX. Compared to the recent teardrop-shaped polymer BTHX, the thermal-hydraulic performance of the proposed BTHX is significantly improved. Regarding the polymer thermal conductivity, it is found that the thermal performance degradation can be minimized with at least 8.0 W·m−1·K−1 of the thermal conductivity. The flow field of the proposed polymer BTHX is also discussed and shows that the unique structure of the sinusoidal wavy tube can reduce the air-side pressure drop and promote the mixing of the air flow, thereby improving the air-side convective heat transfer.

Re-distribution of residual stress in polymer extrusion: An eccentric approach

The development of residual stresses in plastic pipes due to post-die cooling rate differences of the polymer melt was investigated using concentric and eccentric circular geometries in the shape of an annular tube. Heat transfer simulations were performed to understand the effect of non-uniform wall thickness on the temperature and residual stress profiles of melt solidified polymers. Residual stress measurements and thermal analysis of the end products and heat transfer simulation of the post die cooling process were evaluated to understand the change in stress state in the polymer products as a function of temperature. This was done through an example of extruded high-density polyethylene pipes using an industrial scale extrusion line. The outcome of this research helps better understanding of the melt solidification process and its effect on application related properties in a way that was never presented before.

진공 압력에서 전열관 형상에 따른 R718의 막응축 열전달계수에 관한 실험적 연구

진공 압력에서 전열관 형상에 따른 R718의 막응축 열전달계수에 관한 실험적 연구

(Keynote) Actual Pore Morphology of Anodic Alumina Films: Straight or Branching?

Anodic oxide film on aluminum has attracted attention as a starting structure for nanomaterials because of its nano-sized straight tube shape. In this case, a straight pore of the films formed in oxalic acid electrolyte or sulfuric acid electrolyte is generally used. On the other hand, a film with a branched pore structure, like a chromic acid film, is used for practical aluminum materials such as aircraft alloy containing silicon and copper. This is because the branching action of the pores has the effect of suppressing the inhibition of uniform film growth due to the non-uniform base composition of the alloy material. Although the branched structure of the chromic acid film is considered to be unique as anodic film, it has been revealed that when the solubility of the electrolyte is low, the pore branching often appears accompanied by minute dielectric breakdown [1, 2].Recently, however, the authors found that by performing detailed TEM observation of the pore wall of anodic films, considerable branching of the pores occurred even when electrolysis was performed at 40 V in oxalic acid electrolyte, which is the self-ordering condition. The branching of the pores stops at the early stage of the process and remains as traces in the pore walls as radial fine pores. When the subsequent anodic oxidation continues, these radial micropores disappear due to chemical dissolution reaction of the oxide to the electrolyte. In this study, the actual morphology and controlling factors of pore branching in not only chromic acid electrolyte, but also of pore branching found in films formed by other typical anodizing electrolytes such as sulfuric acid, oxalic acid and phosphoric acid will be reported.[1] S. Ono, S. Chiaki, T. Sato, J. Surf. Finish. Soc. Jpn, 26, 456 (1975) DOI:10.4139/sfj1950.26.456[2] S. Ono, T. Kawaguchi, H. Ichinose, Y. Ishida, N. Masuko, J. Surf. Finish. Soc. Jpn, 40, 1361 (1989) DOI:10.4139/sfj.40.1361

PERANCANGAN ALAT TANAM BENIH PADI SEMI OTOMATIS MENGGUNAKAN METODE QUALITY FUNCTION DEPLOYMENT STUDI KASUS PETANI DI KECAMATAN BALONGPANGGANG, GRESIK

Indonesia is an agrarian country where most of the population works in agriculture or farming, and the crops planted by farmers in Indonesia are rice, but in the process of planting it still uses traditional tools, it is very time-consuming, cost and labor of farmers is very ineffective and inefficient in the processing. By using the method of distributing quality functions, it is hoped that semi-automatic rice seed planting products can be created which can reduce the performance of farmers. In the data collection process consisted of 50 respondents who worked as farmers in Balongpanggang sub-district, Gresik Regency. And get the results of the technical characteristics of this product include the shape of the circle tool, the shape of the hand grip tube, the hole is automatically obtained, the color of the tool is black, 12 holes planting holes, the material for holes is using iron, no need for tools, permanent planting hole, using stainless spring , handwork using iron wrapped in rubber, the length of the flexible tool, the design is minimalist and simple, the distance between holes 20 cm, the capacity of the seeds of 3 kg and the main wheel material PVC pipe. And requires a manufacturing fee of Rp. 665,500.00. This semi-automatic rice seed planting tool has the advantage of having 2 planting grooves that apply the principle of planting legowo rows and the price of relatively affordable products.

Performance comparison of tube and plate-fin circular and elliptic heat exchangers for HVAC-R systems

This work seeks to improve HVAC-R systems technology by experimentally quantifying energy efficiency increase due to the utilization of elliptic instead of circular tubes in the evaporator. For that, a performance comparison is conducted in a 12000-Btu h−1 split air conditioning system. A finned elliptic tubes evaporator was built in the laboratory, based on the optimized geometry found in previous studies published by the same authors for maximum heat transfer density, i.e., S/2b, e,φfopt≅(0.5, 0.6, 0.094), which accounts for tube-to-tube spacings, tube eccentricity and fin density. The finned circular tubes evaporator (e = 1) was also built in the laboratory to replace the original component made by the equipment manufacturer, with S/2b = S/D, e,φfopt≅(0.5, 1, 0.094), i.e., same tube-to-tube spacings, and fin density as the elliptic evaporator. In this way, the two heat exchangers had the same shape to minimize their geometric differences. Additionally, the evaporators were designed to fit in the same evaporator unit as the original evaporator, with exactly the same external shape and number of tubes, thus the refrigerant circuit was the same, being the only component to be replaced in the experimental apparatus for comparing the two systems. The objective functions utilized for performance comparisons were the coefficient of performance, COP, and the dimensionless heat transfer volumetric density, q~. The experiment was carried out through the operation of the system installed as specified by the manufacturer, with the evaporation unit placed inside a test chamber, and the condenser unit in a surrounding environmentally controlled ambient. The compressor energy consumption was directly measured by an electric power meter. The results indicate that the optimized elliptic in comparison to the circular geometry shows a gain of approximately 13 and 15% in Q̇evap, 9 and 13.5% in COP, 12.5% and 19.2% in qevap″, 13% and 16.6% in h¯, 14.3% and 16.7% in St¯, and 11.4 and 14.5% in q~, for Re2b = 1030 and 2060, respectively. In conclusion, the sole gain due to the elliptic with respect to the circular geometry is significant. An empirical correlation was introduced to extend the validity range of a previous one to 1030⩽ReD=Re2b⩽10600, and was made available for design engineers in order to predict heat transfer performance. The more the heat exchanger geometry departs from the optimized one, i.e., in terms of tube-to-tube spacings and fin density, the higher the gains are expected to be.

Colloid particles in microfluidic inertial hydrodynamic ratchet at moderate Reynolds number.

The movement of spherical Brownian particle carried by an alternating fluid flow in a tube of periodically variable diameter is investigated. On the basis of our previous results [Phys. Rev. E 99, 012604 (2019)10.1103/PhysRevE.99.012604] on the hydrodynamics of the problem, we look at the competition of hydrodynamics and diffusion. We use the method of Fick-Jacobs mapping on an effective one-dimensional problem. We calculate the ratchet current and show that is is strictly related to finite size of the particles. The ratchet current grows quadratically with particle radius. We also show that the dominant contribution to the ratchet current is due to inertial hydrodynamic effects. This means that Reynolds number must be at least of order one. We discuss the possible use for separation of particles by size and perspectives of optimization of the tube shape.

Simplifying the creation of iron compound inserted, nitrogen-doped carbon nanotubes and its catalytic application

The applicability of metals or their compound inserted, nitrogen-doped carbon nanotubes is blocked by the production although that its unique properties are outstanding in many fields. In this report, a synthetic strategy is developed to carbonize melamine in a CaCl2/FeCl3 molten salt medium and to prepare uniform iron or iron compound (including Fe3O4, Fe3C and Fe) inserted nitrogen-doped carbon nanotubes. The mechanism study of forming Fe3C@NCNTs find that the nanotubes with uniform structure are obtained from graphite sheets, which are formed at a relatively low temperature, and then the obtained graphite sheets transfer to tube shape with the catalysis of Fe at high temperature. The high catalytic activity of Fe3C@NCNTs is demonstrated by an onset oxidation potential of 0.27 V (vs. RHE) in the hydrazine oxidation reaction and an onset potential of 0.96 V (vs. RHE) for the oxygen reduction reaction. Based on DFT calculations, the good catalytic activity of Fe3C@NCNTs may be related to the decreased local work function on its surface. Fe3C@NCNTs also exhibit an enhanced reaction kinetics at higher potential, which make it a promising bifunctional catalyst for direct hydrazine fuel cells.

Effect of tube shape on thermo-fluid performance of a winglet supported fin-and-tube heat exchanger having staggered tubes

Abstract The heat transfer and pressure drop performance of a fin-and-tube heat transfer surface has been presented in this paper. The circular and elliptical tube geometries have been considered for the present analysis. The two tube geometries are compared for both baseline (without winglet) and winglet supported fin-and-tube heat transfer surface. Three staggered tube rows have been considered and rectangular winglets have been selected as heat transfer enhancement tool. The heat transfer and pressure drop performance of the heat transfer surface has been described in terms of Nu and f respectively. To account for the combined effect of Nu and f, an enhancement factor η has also been presented. The winglets are placed at three different stream-wise locations with respect to the tubes and optimum winglet locations for both the tube geometries are presented based on the highest enhancement factor.