Tube Length Research Articles

Experimental investigation of heat transfer coefficient and frictional pressure drop in flow boiling of R513A: Comparative analysis of micro-fin and smooth tubes

The heat transfer coefficient (HTC) and frictional pressure drop (FPD) of R513A in flow boiling conditions experimentally investigated in the present article. The study employed micro-fin tubes (MFT1 and MFT2) and smooth tubes (ST1 and ST2) as testing tubes under various operational parameters. The test sections featured standardized tube lengths (1000 mm) and outer diameter (9.52 mm) across all tubes, with variations in mass flux (50–300 kg·m−2·s−1), vapor quality (0.02–0.96), saturation temperature (12°C, 17°C, and 22 °C) and heat flux (6, 18, and 30 kW·m−2). Research focused on evaluating influence of micro-fin enhancement on flow boiling characteristics, specifically comparing HTC and FPD between micro-fin and smooth tubes. Results indicate significant improvement on HTC within micro-fin tubes compared to smooth tubes, accompanied by reasonable increase in FPD. Additionally, the study validated experimental data against established correlations and conducted sensitivity analysis to understand influence of key parameters on HTC and FPD. Overall, findings contribute valuable insights for optimizing heat exchanger design and thermal system efficiency in flow boiling applications.

Glucose Oxidation Performance of Zinc Nano-Hexagons Decorated on TiO2 Nanotube Arrays

Electrochemically anodized TiO2 nanotube arrays (NTAs) were used as a support material for the electrodeposition of zinc nanoparticles. The morphology, composition, and crystallinity of the materials were examined using scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) was performed to evaluate the electrochemical properties of TiO2 NTAs. Annealing post-anodization was shown to be effective in lowering the impedance of the TiO2 NTAs (measured at 1 kHz frequency). Zinc nanohexagons (NHexs) with a mean diameter of ~300 nm and thickness of 10–20 nm were decorated on the surface of TiO2 NTAs (with a pore diameter of ~80 nm and tube length of ~5 µm) via an electrodeposition process using a zinc-containing deep eutectic solvent. EIS and CV tests were performed to evaluate the functionality of zinc-decorated TiO2 NTAs (Zn/TiO2 NTAs) for glucose oxidation applications. The Zn/TiO2 NTA electrocatalysts obtained at 40 °C demonstrated enhanced glucose sensitivity (160.8 μA mM−1 cm−2 and 4.38 μA mM−1 cm−2) over zinc-based electrocatalysts reported previously. The Zn/TiO2 NTA electrocatalysts developed in this work could be considered as a promising biocompatible electrocatalyst material for in vivo glucose oxidation applications.

Residence time density (RTd) identification through deconvolution of finite time horizon input output data and its Application to a novel analytical dispersion process RTd model

This work presents first an approach to the identification of Residence Time density (RTd) and Residence Time Distribution (RTD) functions, through deconvolution of finite time horizon, input/output data generated by a zero-order hold input, using the novel concept of zero-order hold, average, impulse response coefficients. Subsequently, a novel RTd analytical expression is derived for an open-open axial dispersion process with a finite experimental section in a tube of infinite length, and an explanation is provided for this RTd model’s differences from the literature. This new RTd expression is then employed in two case studies to demonstrate the effectiveness of the proposed identification through a deconvolution conceptual framework in identifying RTd model parameters, and in assisting in the selection of RTd models which are compatible with experimental data.

Evaluation of heat transfer enhancement effect at the hot/cold end of a Stirling engine using performance improvement factor

The driving force of a Stirling engine comes from the heating expansion and cooling compression of working medium. The enhancement of heat transfer capacity of the hot/cold end is the key to improve the Stirling engine performance, while how to objectively evaluate the heat transfer enhancement effect is a precondition. Herein, a polytropic model of a Stirling engine thermal cycle process was firstly established. A method for evaluating the heat transfer enhancement performance under oscillating flow was proposed based on the efficiency and power improvement of a Stirling engine. This method was further used to evaluate the heat transfer enhancement effect of a novel four-leaf helical heating tube under oscillating flow, the efficiency and power improvement factor of which was reached 13.5 % and 6.1 %, respectively. The results show that the efficiency and power improvement evaluation criterion was more comprehensive and intuitive in evaluating the heat transfer enhancement performance under oscillating flow compared with the conventional evaluation indictor like performance evaluation criterion and equivalent tube length and tube number criterion.

Numerical study of the influence of structural parameters on the performance of annular ejector

Abstract Compared with the central ejector, the annular ejector is widely used in refrigeration, coal mining and chemical industry because the working fluid enters the suction chamber through the annular nozzle, the contact area with the ejection fluid increases, and the ejection fluid does not need to change the flow direction. In order to solve the problem of low performance of annular gas ejector, this paper designs an annular gas ejector with reference to the relevant model, and the axial length and suction angle of the mixing tube of the annular gas ejector are mainly studied. The results show that there is an optimal value for the length of the ring gas ejector mixing tube, and the length of the mixing tube is too long or too short is not conducive to the gas extraction of the ring gas ejector. Under the same annular gap, with the increase of the jet angle, the amount of gas consumed in the primary stream does not change much, and the gas to be pumped decreases, resulting in the performance of the annular gas ejector being reduced, which is not conducive to the suction of the ejector.

Study on the refrigeration performance of a miniature pulse tube cryocooler driven by a gas bearing compressor

Recent advancements in long-term space exploration, maintenance-free miniature-satellites and drone infrared detections have created a large demand for highly reliable and miniaturized cryocoolers working at 77–150 K. The pulse tube cryocooler (PTC) has no moving part at the cold end, and if driven by a gas bearing linear compressor which has no mechanical fatigue risk, a refrigeration system with high reliability and compactness will be generated. However, very few researches on the cooling performance of PTC driven by gas bearing linear compressor have been reported. In this study, a miniature PTC and gas bearing compressor are developed, with a weight of the whole refrigeration system about 0.97 kg. The maximum cooling capacity reaches 1.73 W at 77 K with input electric power of 66 W. The cooling capacity per unit weight for this cryocooler is 1.78 W/kg at 77 K, which is the highest compared to those of the existing typical miniature cryocoolers, showing its remarkable lower mass for refrigeration. In addition, the influence of the hot end heat dissipation temperature on the cooling performance is studied. It is found that the heat dissipation temperature of the hot end has a significant effect on the cooling performance. For every 10 K decrease in the hot end temperature, the maximum cooling capacity at 77 K increases by 3.45 % to 13.28 %, the relative Carnot efficiency rises by 4.38 % to 12.59 %. Besides, in the miniature PTC, the cooling performance is very sensitive to the length of the inertance tube, even a small change of 10–20 mm on the length of the inertance tube will lead to obvious effect on the optimum frequency and cooling performance of the system. These results will be helpful for the further research and development of the miniature pulse tube cryocoolers.

Thermal-hydraulic analysis of once-through steam generator with annular narrow slot tube

Integrated small modular reactors (SMR) have garnered significant attention in the field of nuclear energy, with the high-performance integrated steam generator being a critical technology for their advancement. The high-performance once-through steam generator (HP-OTSG) featuring an annular narrow slot tube, which leverages narrow channel enhanced heat transfer technology, holds significant potential for future applications. However, research on the design and experimental studies related to this type of steam generator remains significantly limited. This paper establishes a thermo-hydraulic analysis method for the OTSG based on the segmented heat exchanger design ideas, and the analysis method is verified by comparing the calculation results with those in the literatures. Then, the experimental studies conducted in the annular narrow slot tube and the related conclusions are comprehensively reviewed and subjected to an accurate assessment. The design parameters of a typical SMR, 200 MW Nuclear Heating Reactor-II (NHR200-II), are selected to evaluate and analyze the accuracy and validity of the correlation based on the annular narrow slot tube in the different heat transfer regions including the onset of nucleate boiling (ONB) point, saturated boiling heat transfer coefficient (hsat), dry-out point, and the post-dryout heat transfer coefficient (hpdo). Finally, the influences of operational and geometrical parameters on the performance of the HP-OTSG are analyzed, and the design optimization of the HP-OTSG is performed according to several performance indicators including Power Density (PD), Area Density (AD), pressure drop (Δp), secondary steam temperature (T2out), heat transfer factor (j), the proportion of nucleate boiling zone length in H (PNL), the point of dry-out (Xdryout), and the length of heat exchange tube (L). The model developed in this paper extends the application range of high-performance steam generators to annular narrow slot tubes. The calculation model including both of the analysis method and the heat transfer correlations established in the present study can serve as a useful tool for the design and optimization of HP-OTSG, which further prompts the development of integrated SMR with built-in steam generator.

Mentha choujunensis, a new species from Indian Trans-Himalayan region of Ladakh

Mentha choujunensis (Lamiaceae), a new species from Suru valley of district Kargil in Ladakh, Trans-Himalaya, India is described here. The new species can be distinguished from its closest congeneric M. longifolia in possessing prostate stem, leaves petiolate and ovate to ovate-lanceolate, sparsely pubescent, trichomes 1-celled on adaxial side and 2-celled on abaxial side, base oblique, margin serrate, calyx less than half the length of corolla tube, 8–10 veined, calyx teeth reddish brown with distal trichomes 3–4 celled long and corolla white. Photo-illustrations, comparison of diagnostic characters of the new species with M. longifolia and taxonomic key for the Indian species under section Mentha are provided to facilitate field identification.

Оценка степени высвобождения и токсичности соединений цинка, используемых в фармацевтических и косметических средствах

The degree of release from ointments and the toxicity of three zinc compounds were assessed to establish their minimum sufficient concentration in antibacterial pharmaceutical and cosmetic products. The properties of zinc oxide (ZnO), zinc pyrrolidone carboxylate (ZnРСА) and zinc salicylate (Zn(Sal)2·2H2О) were compared. The release rate of active substances from petrolatum-based ointments (the mass fraction of zinc compounds is 1%) was determined by the Kruvchinsky method. A cellophane film for dialysis served as a semipermeable membrane, which was fixed on a glass tube (length 15 cm, cross section 20 mm2). A sample of ointment (2.00 g) was applied to the inner surface of the membrane. The dialysis tube was inserted into a beaker with dialysis medium and immersed to a depth of no more than 3 mm. The toxicity of aqueous solutions (distilled water) of zinc compounds was determined in a bioluminescent biotest using “Ecolume” bacterial preparation based on a non-pathogenic strain of Escherichia coli. It was found that a high level of toxicity of is achieved at 10-5 mol/dm3 zinc salts in a solution, zinc oxide – 10-4 mol/dm3. A similar amount of Zn2+ diffuses from ointments through a semipermeable cellophane membrane used for the study of dialysis into a 50% aqueous alcohol solution. Zinc ion release from ointment with ZnO was only 0.31%, as well as from ointments with ZnPCA and Zn(Sal)2·2H2О – 1.59% and 1.87% respectively. Thus, the tested approach is economically and environmentally effective, as it allows you to determine the lowest effective concentration of active substances, reducing the burden on the human microbiome and the environment.

FmRbohH Mediates ROS Generation and Enhances Pollen Tube Growth in Fraxinus mandshurica

Flowering plants require normal pollen germination and growth to be fertilized, but studies on the mechanism regulating pollen tube growth in Fraxinus mandshurica are limited. Here, we used transcriptomic data to study the oxidative phosphorylation pathway during pollen tube growth in Fraxinus mandshurica. Our study identified 8,734 differentially expressed genes during the stages S1 to S3 of pollen tube growth. Significant enrichment of the oxidative phosphorylation pathway, amino acid synthesis, protein processing in the ER, carbon metabolism, pyruvate metabolism, citrate cycle (TCA cycle), and glycolysis/gluconeogenesis were examined using the Kyoto Encyclopedia of Genes and Genomes, and 58 genes linked to ROS synthesis and scavenging during the S1–S3 stages were identified. Also, H2DCFDA staining confirmed ROS formation in the pollen and the pollen tubes, and treatment with copper (II) chloride (CuCl2) and diphenyleneiodonium (DPI) was shown to reduce ROS in the pollen tube. Reduction in ROS content caused decreased pollen germination and pollen tube length. Furthermore, FmRbohH (respiratory burst oxidase homolog H) expression was detected in the pollen and pollen tube, and an antisense oligodeoxynucleotide assay demonstrated reduced ROS and pollen tube growth in Fraxinus mandshurica. This study shed more light on the RbohH gene functions during pollen tube growth.

An investigation on seismic performance of the separated fluid inerter base on model experiment and shaking table test

Fluid inerters have gained attention in structural vibration control for their simplicity, durability, high energy dissipation, and significant apparent mass amplification. This study presents an innovative design of a separated fluid inerter, which enhances inertial force, allows for more flexible installation methods, and supports a wider range of connections. A mechanical model is developed and experimentally validated for the separated fluid inerter. The effects of key design parameters on the device's mechanical properties are examined, with a focus on the radii (r1) and length (l) of the helical tube and the radii (r2) of hydraulic cylinder. Theoretical and experimental results confirm the model's reliability and the sensitivity of the device to these parameters. Additionally, a combination of the separated fluid inerter with anti-overturning rolling isolation is applied to a frame structure, and its seismic performance is evaluated through the shaking table test. The results indicate that the separated fluid inerter can effectively reduce the displacement of the isolation layer without significantly increasing the top floor acceleration of the frame structure equipped base isolation (FS-BI).

Proposal and parametric investigations of square steel tubes as post-tensioned connectors for linear-shaped precast concrete elements

Given the pivotal role of connections in the progress of the precast building industry, issues such as costs, chain collapse, and low robustness in all degrees of freedom are critical considerations. This study draws inspiration from Concrete Filled Steel Tube Elements to design and investigate using simple steel tubes as joints for precast linear-shaped elements. The study proposes and examines uncomplicated joints where two precast reinforced concrete beams are positioned within the tube. The encompassment of the beams by the tube, combined with the application of post-tensioning forces, creates a sturdy integrity between the beams, resembling a head-to-head joint. Through 48 experimental tests, various connection parameters such as beam and tube cross-section height, re-bar quantity, tube thickness, and length were systematically investigated. The experimental setup utilized a three-point bending-shear testing configuration, and the results were compared with monolithic references. The findings demonstrate that these adaptive and ductile connections rapidly exhibit a capacity similar to that of monolithic exact beams. All studied parameters exhibited their influences on the capacity of the connection; however, the primary determinant is the length of the tube. Within the discussed range, the tube length should be at least twice as long as the height of the beam. Failing to meet this criterion would prevent the complete manifestation of the desired failure mechanism.

Characterization of Bipolaris bicolor germination: effects of a physical factor on fungal adaptability.

Studies on physiological responses to stimuli from physical factors are essential for understanding the dynamics of the microorganisms and higly important for the management of plant diseases. Besides, the development of an epidemiological model for pathogen populations requires studying their physiological responses to physical stimuli. The objective of this study was to evaluate the germination dynamics of spores from six isolates of Bipolaris bicolor under effects of light at 25°C. Suspensions of 1.6 × 105 conidia mL- 1 from the B. bicolor isolates were inoculated onto Petri dishes containing agar-water culture medium and incubated in a BOD chamber under two physical conditions: (a) constant darkness and (b) constant light for five hours. The study was conducted in a completely randomized design, with a 6 × 2 factorial arrangement (six B. bicolor isolates and two physical conditions) and five replications. The length of the germ tube was measured hourly. The constant darkness resulted in higher mean germ tube growth for the pathogen; however, differences in the final germination percentage were found among the isolates. The isolate F-24-02 exhibited the highest germination adaptability to constant darkness, presenting the longest germ tube length.

Numerical simulation of heat transfer phenomena in a microchannel evaporator for a transcritical CO2 air conditioning system

This study presented a numerical simulation of heat transfer characteristics in a microchannel evaporator for a transcritical CO2 air conditioning system, and the simulated results have been validated by the experimental data. The evaporator consists of 6 passes with 29 flat tubes. Each flat tube has 10 microchannels having a 1.2 × 0.6 mm cross-section. The two-phase flow was simulated in the range of evaporation temperatures from 5 to 15 °C; the mass flow rates of 24.16, 30, and 34.96 g/s; and inlet vapor qualities of 0.5, 0.61, and 0.75, respectively. The results show that the two-phase flow with the evaporative temperature at the inlet of 5, 10, and 15 °C became superheated at the 3rd, the 4th, and the 5th pass, respectively. At the evaporation temperature of 15 °C, the heat transfer coefficient decreases from 8.1 to 3.6 kW/m2 K as the vapor quality increases from 0.75 to 1. With the mass flow rate of 30 g/s, in the tube length range from 0 to 1.1 m, the heat flux achieved around 1.55 kW/m2. The numerical cooling capacity gets the maximum value of 2.85 kW at the evaporative temperature of 10 °C. The numerical results are in good agreement with those obtained from the experimental results and the other published results, with a deviation of less than 10%.

Enhanced Glycerolysis of Fatty Acid Methyl Ester by Static Mixer Reactor.

This study investigates the synthesis of monoglycerides (MGs) and diglycerides (DGs) from glycerol (G) and fatty acid methyl ester (FAME) using a static mixer reactor (SMR), which combines a static mixer (SM) with a reactor tank. The SMR integrates Kenics static mixers (KSM) and low-pressure drop static mixers (LPDSM) with varying length-to-diameter ratios (L/D = 1.0 and 1.5). Keys glycerolysis parameters, including the G:FAME molar ratio of 2:1-3:1, 2-3 wt % potassium hydroxide (KOH), and reaction time of 30-90 min at 150 °C were systematically explored. The SMR design allows precise control over the reaction time without altering the feed flow rate or tube length and avoiding agitator leakage. The optimal operating conditions, determined through a face-centered central composite design, resulted in 71.35% MGs and 14.20% DGs at a 3:1 molar ratio of G to FAME, 3 wt % KOH, 60 min, and 150 °C using an LPDSM with an L/D of 1.5. In comparison, an LPDSM with an L/D of 1 achieved 79.28% MGs and 10.17% DGs under the same conditions. When applied to purified crude glycerol, these conditions yielded 61.09% MGs and 23.44% DGs. The study found that a lower L/D ratio improved the mixing efficiency but increased the pressure drop. The SMR demonstrated superior performance in glycerolysis compared with conventional stirred tank reactors and ultrasonic probe reactors, indicating its potential for enhanced industrial application.

Surface loss probability of atomic oxygen on silica under atmospheric-pressure CO2

Abstract The surface loss probability γ O of atomic oxygen was measured for SiO2 in atmospheric-pressure CO2 and Ar/CO2(3.05%) mixture at 300 K. O atoms were produced via the photolysis of CO2 using a 172 nm Xe2 excimer lamp. After irradiation by Xe2 lamp, the working gas flowed through a quartz tube, causing O atoms to be lost on its inner surface. By measuring the density of O atoms at the end of the tube for different tube lengths, we obtained the value of γ O on the inner surface of the tube. The measured value was 5.5 × 10 − 4 ± 50 % , which falls within the range of referred values of γ O ( 1 × 10 − 5 to 1 × 10 − 3 ) at 4 to 1300 Pa measured using low-pressure O2 plasmas. Despite the 2 to 5 orders of magnitude pressure difference, no significant difference in γ O was obtained. The potential influence of the difference in background gas (CO2 and O2) on the value of γ O was also considered.

Experimental study on the matching relationship of gas wave oscillation tube under liquid-carrying condition

The gas wave oscillation tube (GWOT) transfers energy directly between gases of varying pressures using non-constant motion waves, and its low rotational speed operation offers a broader application potential in two-phase refrigeration compared to turbomachinery. The GWOTs achieve a high performance by optimizing the relationship between tube length, deflection displacement, rotational speed, and incident excitation wave (S1) velocity. However, under the liquid-carrying conditions, the optimizing matching relationship of the GWOTs deviates, leading to a decline in performance, so it is necessary to explore the matching relationship of the high performance of the GWOTs under the liquid-carrying conditions. This study focuses on "spoon" GWOTs, analyzing the impact of rotational speed, liquid-carrying capacity, and deflection displacement on their refrigeration performance under a fixed tube length through experimental analysis. It is found that the refrigeration efficiency at the design parameters of the GWOTs decreases by a maximum of about 25 % with the increase in the amount of liquid-carrying capacity within the study area of this paper, while the refrigeration efficiency can be improved by a maximum of about 8 % by varying the rotational speed. The findings provide valuable insights for enhancing the liquid-carrying performance of the GWOTs and promoting the application expansion of GWOTs in the field of gas-liquid two-phase.

Endothelial extracellular vesicles enhance vascular self-assembly in engineered human cardiac tissues.

The fabrication of complex and stable vasculature in engineered cardiac tissues represents a significant hurdle towards building physiologically relevant models of the heart. Here, we implemented a 3D model of cardiac vasculogenesis, incorporating endothelial cells (EC), stromal cells, and human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CM) in a fibrin hydrogel. The presence of CMs disrupted vessel formation in 3D tissues, resulting in the upregulation of endothelial activation markers and altered extracellular vesicle (EV) signaling in engineered tissues as determined by the proteomic analysis of culture supernatant. miRNA sequencing of CM- and EC-secreted EVs highlighted key EV-miRNAs that were postulated to play differing roles in cardiac vasculogenesis, including the let-7 family and miR-126-3p in EC-EVs. In the absence of CMs, the supplementation of CM-EVs to EC monolayers attenuated EC migration and proliferation and resulted in shorter and more discontinuous self-assembling vessels when applied to 3D vascular tissues. In contrast, supplementation of EC-EVs to the tissue culture media of 3D vascularized cardiac tissues mitigated some of the deleterious effects of CMs on vascular self-assembly, enhancing the average length and continuity of vessel tubes that formed in the presence of CMs. Direct transfection validated the effects of the key EC-EV miRNAs let-7b-5p and miR-126-3p in improving the maintenance of continuous vascular networks. EC-EV supplementation to biofabricated cardiac tissues and microfluidic devices resulted in tissue vascularization, illustrating the use of this approach in the engineering of enhanced, perfusable, microfluidic models of the myocardium.

Combination of control factors influencing application uniformity of a low-pressure pivot sprinkler spray unit

The objective of any pivot irrigation system is to ensure uniformity of application of water which can be achieved when responsible factors such as pressure, drop tube lengths, nozzle size etc. are adequately designed. This indoor experiment conducted in a 44m2 laboratory facility tends to evaluate the extent of the influence of some sprinkler design parameters on the performance of a low pressure single pivot sprinkler spay unit. The parameters considered are; pressures of 9,12, 15 and 19Psi, nozzle sizes of 4.17, 5.56, 6.95 and 8.14 mm and drop tube lengths of 1, 1.2 and 1.5m. In this experiment an inverted U-shaped frame designed to support a spray sprinkler at different heights was used. The hydraulic installation with manual throttle valves for controlling water distribution was used to supply pressurized water to the spray model sprinkler. A number of 64 graduated catch-cans with 0.16 m diameter and 0.2m height were used. The cans were arranged in eight radial legs with a distance of 1m apart. The system was run for one hour then the caught volumes were measured manually using a graduated cylinder with a capacity of 500 mL. The catch-cans data were used to determine uniformity coefficients. Line graphs were used to show relationships between the parameters measured. The experiment shows that there is strong relationship between the parameters considered. It indicated that the coefficient of uniformity (CU) and distribution uniformity of lower quarter DUlq increases with increase in nozzle size and pressure. It also shows that the largest nozzle size and pressure within the limits of this experiment gave the best CU and (DUlq) values of 96% and 90% at 1.5m height. Lager nozzle sizes with lower pressure reduces the CU and DUlq values. It is concluded from this experiment that though pressure, nozzle size and height of application influences the uniformity of application, larger nozzle sizes accompanied by higher pressure and height of application resulted in good uniformity of application. It is therefore imperative that while operating Pivot Sprinkler systems, careful selection of nozzle diameters, operating pressure and drop tube heights, sprinkler can be used to apply the ideal amount of irrigation water needed to refill the crop root zone that can neither cause runoff nor harm the crop and also provide the best uniformity possible under the prevailing wind and management conditions.

Plant extracts to manage the parasitic weed branched broomrape (Phelipanche ramosa)

Some weeds have parasitic lifestyles, causing severe problems in agriculture. These plants include Phelipanche ramosa (L.) Pomel (branched broomrape). Greenhouse and nursery trials were carried out to assess control of P. ramosa using organic extracts from 14 plant species. The parameters recorded were counts of living and dead tubercles of P. ramosa and fresh weights of living tubercles. Organic extract of Olea europea reduced lengths of germ tubes during P. ramosa seed germination, and extracts of Bidens bipinnata and Dittrichia viscosa reduced production and development of the parasite’s tubercles, with very encouraging results in reducing seed germination rates. This research provides knowledge insights on the potential use of plant secondary metabolites to limit spread of P. ramosa, addressing an increasing challenge for organic crop production.