Spiral Ribs Research Articles

Mechanism of Condensation Enhancement by Corrugated Low Finned Tubes in Presence of Noncondensable Gas

Corrugated tubes are the most convenient reinforcement techniques to enhance intube condensation. In this paper, the average condensation heat transfer coefficients inside the corrugated low finned tube and smooth tube were firstly introduced. The distribution of local heat transfer coefficient was presented at lower and higher inlet noncondensable gas mass fractions. The results show that the major heat transfer resistance is the thermal resistance of liquid film at lower inlet gas fraction. So the mechanism of condensation enhancement by corrugated low finned tubes is the increase of liquid film condensation coefficient. But at higher inlet gas fraction gas layer mass transfer resistance becomes the control thermal resistance. The spiral ribs inside corrugated low finned tube can thinner not only the gas layer thickness but also the liquid film thickness. The mechanism of condensation enhancement is the increase of both gas layer and liquid film condensation coefficient.

Research on Low Temperature Condensation of Flue Gas from Gas Industrial Boiler

The paper analyzed the heat transfer in the condensing section of condensing gas industrial boiler. As to the operation of boiler, the field test of the flue gas condensing section was carried out where the field test data was compared with the theoretical values to verify the calculation formula of the convective exothermic coefficient of the condensing section in the condensing boiler’s spiral rib.

Cosserat Effects in Achiral and Chiral Cubic Lattices

Abstract Cubic 3D lattices were designed, made by 3D printing, and studied experimentally. One lattice was simple cubic with ribs of diameter 1/5 the cell size. The second lattice was chiral with spiral ribs. The chiral lattice, but not the achiral lattice, exhibited squeeze-twist coupling with size effects. The squeeze-twist coupling cannot occur in a classically elastic solid but is anticipated by theory in a Cosserat solid. Both lattices exhibited size effects in bending and torsion.

Optimization of Tubular Microalgal Photobioreactors with Spiral Ribs under Single-Sided and Double-Sided Illuminations

Microalgae can be raw materials for the production of clean energy and have great potential for development. The design of the microalgal photobioreactor (PBR) affects the mixing of the algal suspension and the utilization efficiency of the light energy, thereby affecting the high-efficiency cultivation of the microalgae. In this study, a spiral rib structure was introduced into a tubular microalgal PBR to improve the mixing performance and the light utilization efficiency. The number of spiral ribs, the inclination angle, and the velocity of the algal suspension were optimized for single-sided and double-sided parallel light illuminations with the same total incident light intensity. Next, the optimization results under the two illumination modes were compared. The results showed that the double-sided illumination did not increase the average light/dark (L/D) cycle frequency of the microalgae particles, but it reduced the efficiency of the L/D cycle enhancement. This outcome was analyzed from the point of view of the relative position between the L/D boundary and the vortex in the flow field. Finally, a method to increase the average L/D cycle frequency was proposed and validated. In this method, the relative position between the L/D boundary and the vortex was adjusted so that the L/D boundary passed through the central region of the vortex. This method can also be applied to the design of other types of PBRs to increase the average L/D cycle frequency.

Four new deep-sea provannid snails (Gastropoda: Abyssochrysoidea) discovered from hydrocarbon seep and hydrothermal vents in Japan.

Recently, the species richness of provannid gastropods inhabiting chemosynthetic ecosystems in the northwestern Pacific has been reassessed, revealing a much higher diversity than previously realized. Here, we describe four further new species, two in the genus Desbruyeresia and two in the genus Provanna. Their generic placement was confirmed by both shell and radula morphology, as well as phylogenetic reconstruction using the mitochondrial cytochrome c oxidase subunit I gene. Desbruyeresia armata n. sp. from vent fields in the Izu-Ogasawara Arc is characterized by a stout shell with numerous tubercles or short spines and marginal teeth coarsely serrated into only four denticles. Desbruyeresia costata n. sp. from Okinawa Trough vents is distinguished from other congeners by an elongate shell with strong axial ribs and obsolete spiral ribs. These represent the first Desbruyeresia species from Japanese waters. Provanna fenestrata n. sp. discovered from two vent fields in the Okinawa Trough is instantly recognizable from its uniquely regular rectangular lattice sculpture; Provanna stephanos n. sp. is a surprising new discovery from the supposedly well-explored ‘Off Hatsushima’ hydrocarbon seep site in Sagami Bay, and is highly distinctive with two characteristic rows of strongly spinous spiral ribs. The discovery of these new species in relatively well-explored chemosynthetic ecosystems in Japan indicates that the biodiversity of such systems remains poorly documented.

Thermal performance improvement using unilateral spiral ribbed absorber tube for parabolic trough solar collector

Enhancing the heat transfer in the absorber tube improves effectively both the thermal efficiency and the structural safety of the parabolic trough receiver (PTR). This study proposed a novel unilateral spiral ribbed PTR (USR-PTR) for enhancing the heat transfer inside the absorber. The flow and heat transfer performance of the proposed USR-PTR was studied numerically using CFD tool coupled with Monte Carlo Ray Tracing (MCRT). A detailed comparison between the USR-PTR and the conventional straight and smooth PTR (CSS-PTR) was conducted in terms of both thermal and hydraulic performance, revealing that fluid disturbance, rotational flow and local longitudinal vortexes induced by the discontinuous spiral ribs are the three main causes of heat transfer enhancement in the USR-PTR. In most cases of the discussed flow rates, the overall performance of the USR-PTR is better than that of the CSS-PTR. The circumferential temperature difference of the USR-PTR can be reduced by up to 25% compared to the CSS-PTR. The structural parameters of the spiral rib influence greatly the performance of the USR-PTR. It is revealed that the improvement of the overall performance of the USR-PTR by changing individually the rib structural parameters, including pitch interval, rib height, corner radius and spiral angle, can be up to 12.5%, 9.8%, 10.8% and 30.1% respectively.

Experimental determination of the heat transfer coefficient in internally rifled tubes

Development of the heat transfer surfaces on the tube inside makes it very difficult or even impossible to determine the heat transfer coefficient analytically. This paper presents the experimental determination of the coefficient in an internally rifled tube with spiral ribs. The tests are carried out on a laboratory stand constructed at the Institute of Thermal Power Engineering of the Cracow University of Technology. The tube under analysis has found application in a supercritical circulating fluidized bed boiler. The heat transfer coefficient local values are determined for the Reynolds numbers included in the range of ~6000 to ~50000 and for three ranges of the heating elements power. As the medium flows through internally rifled tubes with spiral ribs, the heat transfer process gets intensified compared to similar processes taking place in smooth tubes. Based on the obtained experimental data, a correlation is developed enabling determination of the dimensionless Chilton-Colburn j factor. The equation form is selected so that a comparison with existing results of tests performed on rifled tubes can be made. Comparing the Nusselt number values calculated based on the developed correlation with those obtained using other correlations described in the literature, it can be observed that the criterial number is about twice higher. The research results confirm the thesis that the element internal geometry has a sub-stantial impact on the heat transfer process.

A Spiral Seal Method in the Lunar Regolith for Chang’E-5 Drill: Seal Design and Experiment

In the Chang'E-5 mission of the lunar regolith drilling, the gap between the rotary drill bit and the sheath is required to be sealed. In view of the particularity of the lunar subsurface operation, a spiral seal method is proposed based on the analysis of the particles flow state in the clearance, which is made up of the spiral ribs on the inner surface of the drill bit and the friction interface on the outer surface of the sheath. The drilling and sampling simulation is carried out using discrete element method, which verifies the feasibility of the spiral seal in principle. For the test of sealing performance, a test system was developed and drilling and sampling experiments were carried out with several groups of sealing components that have different structure parameters. The test results show that the proposed spiral seal method solves the problem of regolith leakage well in the drilling and sampling process, and it will contribute to the design of the Chang'E-5 drill.

A revision of the genus Littorina (Mollusca: Gastropoda) in Korea

ABSTRACTLittorina Férussac, 1822 is an abundant genus of small gastropods found in the upper littoral zone of rocky seashores worldwide. Although ecologically important, shell-based species identification in this genus is challenging due to phenotypic variation in shell morphology and lack of diagnostic characters among morphologically similar species. In this study, we revised the taxonomy of Korean Littorina species using morphological characters (shell and radula) and cox1 mitochondrial DNA sequences for three Korean species: L. brevicula, L. sitkana, and L. horikawai. Results suggest that L. sitkana was erroneously reported as L. kasatka in a previous study. A new record for Littorina horikawai (Matsubayashi & Habe in Habe, 1979), previously unknown from Korea, is described, which can be distinguished from L. sitkana by the presence of alternating white and brown spiral ribs on each whorl. Comparison of the mtDNA cox1 gene sequences shows very low intraspecific variation even between geographically distant populations. A phylogenetic tree supports a close relationship between L. horikawai and L. sitkana, consistent with earlier phylogenetic studies.

Effects of tool intermittent vibration on helical internal hole processing in electrochemical machining

Ribbed holes can serve to increase the efficiency of the heat exchangers and improve the performance of industrial equipment. Increasing demand for small ribbed holes is a key driver in manufacturing technology research. Electrochemical machining has been shown to be a promising method for this. In this paper, an intermittent low-frequency vibration tool is used to demonstrate significant improvement to the geometry of internal ribbed holes. The process stability, material removal rates, and uniformity of features along the flow direction are improved. Firstly, a 3D model of the flow field within the interelectrode gap was developed to calculate and governing flow regime in the interelectrode gap. The simulation demonstrated that the fluid velocity fluctuates periodically and this enhances electrolyte flushing in the interelectrode gap during the machining process. Then, experimental tests for the manufacture of spiral ribs on small holes (Ø1.5 mm and 20–40 mm depth) are also demonstrated with accompanying variation of the tool vibration amplitude and frequency, respectively. Results show that groove depth was most greatly influenced by the vibration amplitude and that better uniformity could be obtained at higher vibration frequencies. The groove depth increased by 15% over nonvibrating control tests with enhanced uniformity.

Removal of dyes from aqueous solution by sorption with fly ash using a hydrocyclone

Methyl orange is an anionic water-soluble carcinogenic azo dye. Excessive dye concentration in water is a major health concern worldwide. In this current study, experiments have been conducted to remove methyl orange from aqueous solution using fly ash as an adsorbent in a continuous mode by using a hydrocyclone. A spiral rib has been introduced in the cylindrical part of the conventional hydrocyclone to increase the performance and this hydrocyclone is called as a ribbed hydrocyclone. Experiments were carried out to analyse the performance of particle separation and dye removal efficiency of the ribbed hydrocyclone. The cut size d50 of the ribbed hydrocyclone was 21 μm at a slurry flow rate of 50 LPM. Maximum methyl orange removal efficiency was 66% for the initial concentration of 60 mg/l for the dose of 2 g/l at a slurry flow rate of 50 LPM. The novelty of the current study revealed that the ribbed hydrocyclone is more efficient than conventional one and it could be used for the removal of both fly ash and methyl orange in a continuous mode.

Heat Emission and Temperature Non-uniformity in Rod Bundles with Different Spacing, Cooled by Heavy Liquid-Metal Coolant

Heat emission and temperature non-uniformity along the perimeter of rods in free lattices of fuel elements with heavy liquid-metal coolant are studied. The experimental data for an assembly of smooth rods, assemblies of fuel elements with spiral ribbing, and transverse lattices are analyzed. The studies show that there is almost no temperature non-uniformity in a lattice of smooth fuel elements along its perimeter, which is in contrast to the high general azimuthal temperature non-uniformity in an assembly with spacing by spiral coils. Rib spacing resulted in significant reduction of heat emission. In an assembly with transverse spacer lattices, the heat emission increases only in the region containing the lattices; in the spaces between lattices, it is approximately equal to the heat emission in a bundle with smooth fuel elements. Inside a spacer lattice, periodic temperature non-uniformities appear along the perimeter of the fuel elements; these non-uniformities are due to the fuel elements touching the elements of the lattice. A relation is recommended for calculating heat emission (Nusselt numbers) and temperature non-uniformity along the perimeter of the fuel elements for the studied methods of spacing the fuel elements.

Role of vortex finder depth on pressure drop and performance efficiency in a ribbed hydrocyclone

Hydrocyclones are devices used in many chemical and mineral based process industries for separation of fine particles. To enhance the performance efficiency of hydrocyclone with optimum pressure drop several configuration of hydrocyclone is designed and developed. A new hydrocyclone with spiral rib was designed. In the present study, the effects of spiral rib on pressure drop and separation efficiency are investigated experimentally and effect of vortex finder depth of a ribbed hydrocyclone was analyzed. The experimental results showed that the spiral rib has a significant effect on pressure drop and separation efficiency. It is interesting to note that by using a rib in the cylindrical part of the hydrocyclone resulted in lower pressure drop and improved separation efficiency. The pressure drop decreases by 17.5% and total efficiency increases by 10.5% at a feed velocity of 5 m/s and at a vortex finder depth of 7.6 cm. Pressure drop and separation efficiency also affected by the vortex finder depth. In this study, four ribbed hydrocyclones with 6 cm, 7.6 cm, 9.8 cm and 12.5 cm vortex finder depth have been taken for the analysis. Separation efficiency is maximum for the vortex finder depth of 7.6 cm.

나선형 리브의 GFRP 보강근의 부착응력-미끄러짐 관계 평가

이 연구에서는 나선형 리브를 갖는 GFRP 보강근의 부착강도에 대한 설계기준들의 안전성을 평가하고 실험결과에 기반하여 GFRP 보강근의 부착응력-미끄러짐 관계 모델을 제시하였다. GFRP 보강근의 부착응력-미끄러짐 관계를 평가하기 위한 실험변수는 콘크리트 설계 압축강도(20 MPa, 40 MPa 및 60 MPa)와 보강근 직경(6 mm, 9 mm 및 12 mm)이다. GFRP 보강근의 부착강도에 대해 ACI 440 식은 상당히 과대평가하는 경향을 보인 반면, JSCE 식은 상당히 과소평가 하였다. CSA 식은 위 두 설계기준 보다 실험결과와 잘 일치하였지만 콘크리트 압축강도가 53 MPa일 때 다소 과대평가하는 경향을 보였다. 비선형 포물선형의 GFRP 보강근의 부착응력-미끄러짐 관계에 대해 제시된 모델은 비교적 실험결과를 잘 일치하였다.

Removal of fluoride from wastewater using HCl-treated activated alumina in a ribbed hydrocyclone separator

ABSTRACTExcessive fluoride concentration in wastewater is a major health concern worldwide. The main objective of wastewater treatment is to allow industrial effluents to be disposed of without danger to the human health and the natural environment. In this current study, experiments have been conducted to remove fluoride from aqueous solution using alumina and HCl (Hydrochloric acid) treated activated alumina in a continuous mode. A spiral rib was introduced in the cylindrical part of the conventional hydrocyclone to increase the performance, and the new hydrocyclone is dubbed as ribbed hydrocyclone. Experiments were carried out to analyze the performance of the ribbed hydrocyclone and compared the results with the conventional hydrocyclone of the same dimension. The efficiency of conventional and ribbed hydrocyclone at a slurry flow rate of 50 LPM (liter per minute) for the solid concentration of 1.4 wt% were 80% and 93.5% respectively. The cut size d50 of the conventional and ribbed hydrocyclone was 18 µm and 13 µm respectively at a slurry velocity of 50 LPM. Fluoride removal efficiency using alumina and HCl-treated alumina was also investigated in a continuous mode by the ribbed hydrocyclone. Maximum fluoride removal efficiency was 49.5%, and 80% for alumina and HCl-treated alumina for the initial concentration of 10 mg/L at a slurry flow rate of 50 LPM.

Evaluation on the Bond Stress-slip Relationship of GFRP Reinforcing Bars with Spiral Ribs

Evaluation on the Bond Stress-slip Relationship of GFRP Reinforcing Bars with Spiral Ribs

Prospects of the Use of Heat-Exchange Surfaces for the Gas Turbine Plant Regenerators Intensifying the Heat Release by the Ridges and Cavities

The heat regeneration results in an increase in the efficiency factor of gas turbine plant (GTP) on average by 6 to 8% (absolute); however the plant size and mass are increased significantly. In this connection, when designing the regeneration GTP an important task is to reduce the regenerator mass and increase its compactness; one of the ways to the solution of this problem is to make use of intensified heat-exchange surfaces. Joint experimental and computational research done by the Institute for Engineering Heat Physics of the National Academy of Sciences of Ukraine and the state-owned Scientific and Production Company SE Gas Turbine Scientific Production Complex Zorya-Mashproekt allowed us to determine the influence produced by the ridges and cavities of a different shape arranged on external and internal pipe surfaces on the heat release, hydraulic resistance and the tubular regenerator mass. It has been established that the arrangement of holes on the external surface would increase the heat release by a factor of 1.16 to 1.97 with an insignificant increase in the resistance (on average 1.01 times), which will result in the reduction of the mass of heat exchange surface by 33 %. Spiral grooves made on the external surface of the pipes would increase the heat release 1.5–1.9 times with the 21 to 32 % mass reduction. The formation of cylindrical projections on the internal surface of pipes would increase the heat release 1.03–1.5 times and the resistance 1.18–2.85 times which may result both in the mass decrease (by 18 %) and the mass increase (by 27 %). The use of spiral ribs results in 1.75–2.25 times increase in the heat release and 4.05–6.8 times increase in the resistance and the mass is increased by 37 %.

Performance evaluation of a hydrocyclone with a spiral rib for separation of particles

Several design modifications have been done to improve particle separation efficiency in a hydrocyclone. The effects of a rib which is introduced into the cylindrical part of the hydrocyclone are discussed here. CFD (Computational fluid dynamics) is a useful tool to study the velocity and pressure distribution of complex turbulent flow in a hydrocyclone. Flow simulations are carried out using a three-dimensional double precision, segregated, steady-state solver tool. Reynolds stress model is employed for turbulent model which is suitable for the anisotropic turbulent flow. A comparison study for pressure drop and flow velocity for the conventional and ribbed hydrocyclone have done. The obtained CFD simulated results in correlation with experimental data shows that the pressure drop reduces by 13.9% at a velocity of 2.5m/s by using rib. An experimental finding shows that the cut size particle diameter for conventional and ribbed hydrocyclone are 36µm and 28µm respectively at the velocity of 2.5m/s.

Gastropods from the Late Jurassic-Early Cretaceous seep deposits in Spitsbergen, Svalbard.

Eleven gastropod species from seven latest Jurassic-earliest Cretaceous hydrocarbon seep deposits from central Spitsbergen, Svalbard are described and illustrated. Six new species and one new genus are introduced. Sassenfjordia gen. nov. is tentatively classified as a naticoid and is characterized by a naticiform gross teleoconch morphology and a large protoconch ornamented with spiral ribs, similar to those present in the subfamily Sininae. The patellogastropod ?Pectinodonta borealis sp. nov. represents the oldest occurrence of pectinodontid limpets in chemosynthesis-based associations. The colloniid Hikidea svalbardensis sp. nov. is the oldest confirmed occurrence of this genus so far. The eucyclid Eucycloidea bitneri sp. nov. is the second report of an occurrence of this genus at hydrocarbon seeps (both of which come from the Paleo-Barents Sea). Abyssomelania sp. is the third known, and the oldest occurrence of this genus. Hudlestoniella hammeri sp. nov. represents another occurrence of this genus at seeps in the Paleo-Barents Sea; its current higher-rank assignment is reviewed herein. It may belong either to the rissoids, as previously suggested, or to the abyssochrysoids (or zygopleurids). A fossil identified as Cretadmete sp. is here classified in the Purpurinidae, a family of stem neogastropods or tonnoideans. The heterobranch Hyalogyrina knorringfjelletensis sp. nov. is the oldest occurrence of hyalogyrinids in chemosynthesis-based associations. Several oldest occurrences of seep taxa in moderately shallow-water seeps in Spitsbergen suggest that the previously questioned onshore-offshore hypothesis of seep and vent colonization should be carefully re-investigated.

Force conditions of pressing light-alloy drill pipes with spiral ribbing

The equation for calculating the pressing force of drill pipes with spiral ribbing is proposed from the Perlin procedure based on the balance of active and reactive forces. The cross-section of a spiral pipe is presented in a form of a smooth pipe with a screw arrangement of metal fibers and outer spiral edges. A component taking into account the energy spent for the screw motion of metal is added to the formula. It is shown that the compacting force, which is found according to the modernized formula, is 28% larger than for a smooth pipe with the equal area. It is revealed that an increase in the angle of ascent of the rib spiral leads to an increase in force compared with that for longitudinally edged pipes.