Effect Of Tube Diameter Research Articles

Effects of Tube Diameter and Gas Flow Rate on the Discharge Dynamics Characteristics and Reactive Species of Nanosecond Pulsed Discharge Plasma in Contact With Water

ABSTRACTThe use of millimeter quartz tubes to generate non‐thermal plasma in contact with liquid is widely applied in medicine, such as the effective disinfection of catheter tubes and tooth cavities. Here, the effects of tube diameter and gas flow rate on discharge dynamics and reactive species characteristics of nanosecond pulse needle‐water discharge are studied using an ICCD camera and optical emission spectra. The discharge diffusion is increased significantly by an appropriate combination of tube diameter and gas flow rate. Besides, the discharge intensity, emission spectra intensities of reactive species, gas temperature, and electron density increase with the increase of quartz tube diameter and gas flow rate, which contributes to enhance the production of OH and H2O2 species in aqueous samples.

The Effect of Tube Diameter on the Surface Distributions of ROS in Model Tissue Treated with a He + O2 Plasma Jet

The Effect of Tube Diameter on the Surface Distributions of ROS in Model Tissue Treated with a He + O2 Plasma Jet

CFD simulation of liquid food flow in a coiled tube UVC reactor

The coiled tube reactor is the most efficient UVC reactor for disinfecting microorganisms in liquid food flow. Thus, it is critical to investigate the effective parameters for designing a coiled tube UVC reactor. In this study, CFD simulation is used to investigate the turbulent and laminar flow of Newtonian and non-Newtonian fluids. In turbulent flow, disinfection in the tube area is nearly uniform, with the exception of regions near internal lamps, where the most disinfection has occurred. The variation of log10 reduction in terms of tube turn number is linear. Increasing the non-Newtonian behavior increases the disinfection of microorganisms in the reactor. Furthermore, the effect of tube diameter on coiled reactor performance is investigated. Reducing the diameter of the reactor's tubes improves its performance. Finally, two correlations are obtained for the influence of the effective parameters on the log10 reduction of this type of reactor.

The influence of tube diameter parameters on the flow resistance and heat transfer characteristics of supercritical CO2 in horizontal tubes

The diameter parameters of tubes are crucial for the flow and heat transfer characteristics of supercritical fluids. however, the diameter effect has not been fully understood. The existing literatures only investigate the effect of different tube diameters on the flow and heat transfer characteristics within a narrow parameter range, lacking specific theoretical analyses and verification in a wide range of parameters. Therefore, experimental research was conducted to investigate the influence of tube diameter parameters on the flow resistance and heat transfer of supercritical carbon dioxide(sCO2) in horizontal tubes and an explanation of the tube diameter effect mechanism is provided based on pseudo-boiling theory. Stainless steel smooth circular tubes with diameters of 8 mm, 10 mm, and 12 mm were used as the test section, and various experiments were carried out under the range of mass flux (G): 509.23–1267.34 kg/m2s, heat flux (qw): 97.91–410.43 kW/m2, and operating pressure (P): 5.54–20.32 MPa. From the pseudo-boiling theory analysis, the influence of tube diameter parameters has a greater influence on the heat transfer in the two-phase-like (TPL) regime and is almost negligible when the P exceeded 1.5Pc, indicating the interaction between liquid-like (LL) and vapor-like (VL) phases is found to be the dominant reason for the tube diameter effect on heat transfer and the correlations for predicting the maximum wall temperature difference between the top and bottom generatrix (ΔTmax) are established. The present work can significantly enhance the understanding on sCO2 flow boiling mechanism and provide a new research direction for supercritical fluid.

A PARAMETRIC AND COMPARATIVE STUDY ON BARE-TUBE BANKS AND NEW CAM-SHAPED TUBE BANKS FOR WASTE HEAT RECOVERY APPLICATIONS

The present study numerically examines the effects of tube diameter (12 to 35 mm), arrangement, pitch-to-diameter ratio (1.25 to 2.5), length (300 to 1500 mm), and passage number (1-4 passes) on the thermofluidic characteristics of cross-flow tube bundles. Especially, five new cam-shaped tubes are proposed in comparison with the conventional round tube. The air temperatures at the cold and hot side inlets are kept constant at 25°C and 600°C, respectively. The numerical method is verified by the existing experimental results. The findings show that a cam-shaped tube with an equal diameter (Cam_1818) is a promising tube for tube bundles, which apply in waste heat recovery. Indeed, it can offer the same minimum gap as that of the round tube; however, it improves the total thermal resistance up to about 28% and enhances the heat-transfer rate up to an average of 42.3% compared to that of the round tubes at the same pumping power.

Experimental Analysis of Bubble Behavior and Critical Heat Flux During Pool Boiling on Vertical Circular Tubes

Abstract The heat transfer during pool boiling incorporates a higher rate of heat dissipation capability at low-temperature differences. This technique is widely used in the nuclear industry for thermal management. In this study, the effect of tube diameter and length on critical heat flux (CHat atmospheric conditions in saturated water during pool boiling) is analyzed. The tubes of SS 304 are kept in the vertical orientation. The diameter of the tubes ranges from 1.2 mm to 9 mm. The experiments are performed with tubes having lengths varying from 50 mm to 1000 mm. It has been noted that tubes of smaller diameter show a greater magnitude of critical heat flux (CHF) for the given length. Compared to other tubes, the magnitude of CHF for a 1.2 mm diameter is higher. For a given diameter, a longer tube is found to have lower CHF than the ones having lesser length. The variation in the CHF magnitude is negligible for tubes with a diameter of more than 2.5 mm beyond a length of 200 mm. The location of occurrence of CHF is near the bottom end of the vertical tube. The study illustrates the behavior of bubble nucleation for various tube dimensions and heat fluxes. The inception and detachment of bubbles for different tubes are analyzed. The pool boiling regime is categorized and studied basing the behavior of the incepted and departed bubble while maintaining uniform heat flux. A mathematical relation that empirically accounts for the effect of tube dimensions , i.e., length and diameter on pool boiling CHF is proposed. The experimental CHF data obtained during pool boiling are tabulated toward contributing to the CHF databank.

Tuning structural and electronic properties of single wall AlN nanotubes

The electronic and structural characteristics of the armchair and zigzag single-walled AlN nanotubes (SWAlNNTs) have been considered by using density functional theory (DFT). The effects of tube diameter on the Al–N bond length, the buckling separation, tube lengths, valence band maximum (VBM), conduction band minimum (CBM), Fermi energy, strain energy, and bandgap have been studied. The strain energy calculation revealed that higher-diameter nanotubes are more stable than those with smaller diameters consequently at the same chirality armchair AlNNTs are more stable than zigzag types. It revealed a correlation between the bandgap and buckling: the smaller the bandgap, the higher the buckling, and the buckling separation increases by decreasing tube diameter. The 2p-orbitals of Al and N atoms have the most contribution to CBM and VBM, respectively. All zigzag and armchair AlNNTs are semiconductors having direct and indirect bandgap, respectively. It is also found that for both zigzag and armchair AlNNTs, with increasing nanotube diameter, the bandgap increased. The conclusions of this study can definitely be useful in future experimental works on optoelectronic devices.

DFT study of electronic and structural properties of single‐walled gallium nitride nanotubes

AbstractThe electronic and structural properties of the armchair and zigzag single‐walled GaN nanotubes (GaNNTs) are studied by using density functional theory. The effects of tube diameter on the GaN bond lengths, the axial lattice constant, the Fermi energy, the buckling separation, and the bandgap of the tube are investigated. It is revealed that there is a correlation between the bandgap and the buckling; the smaller the bandgap, the higher the buckling. The results show that by increasing diameter of tubes the buckling separation decreases. The 4p‐orbitals of Ga atoms and 2p‐orbitals of N have the main role to the valence band maximum and the conduction band minimum, respectively. All armchair and zigzag GaNNTs are semiconductors having indirect and direct bandgap, respectively. It is also found that by increasing the diameter of nanotubes the bandgap increases, for both armchair and zigzag GaNNTs. The consequences of this study can undoubtedly be useful in future experimental works on optoelectronic devices.

Developing adiabatic two-phase flow after an expansion valve: the effect of tube diameter and oil

The development of the adiabatic two-phase flow between an expansion valve and evaporator along a 600 mm-long glass tube in an air conditioning system has been presented in Yao and Hrnjak (2022). In this paper, the developing two-phase flow in a straight tube of 5 mm inner diameter is compared to that of the 8 mm tube in Yao and Hrnjak (2022) to examine the effect of the tube diameter. R134a with 1.3% of POE 32 is used as the working fluid. It provides a good opportunity to investigate the effect of oil on developing two-phase flow by comparing the results in this paper with Bowers and Hrnjak (2009). They have explored the developing two-phase flow after a needle valve using pure R134a. The flow patterns near the expansion device are affected by both the addition of oil and the structure of the expansion device. For the fully developed flow, the differences in flow patterns are mainly attributed to the oil. A 3D flow pattern map for developing two-phase flow is proposed in this paper. There is no similar research in the open literature to compare with. But the developed flow is compared with the flow pattern maps of Wojtan et al. (2005) and Barbieri et al. (2008).

Developing adiabatic two-phase flow after an expansion valve: Flow development in an 8 mm tube

This paper presents the developing two-phase flow after an expansion valve. R134a with 1.3% POE32 is used as a working medium. The flow patterns are visualized from 15 mm until 595 mm after the expansion valve in a straight tube with an inner diameter of 8 mm. The experiments cover the mass flux from 100 to 480 kg m−2 s−1 and the range of quality from 0.002 to 0.500. The observed flow patterns are classified into four regions as two-phase flow progresses along the tube: well-mixed, separating, separated but developing, and fully developed. Due to the sudden expansion in TEV, the flow structure in the well-mixed region is similar to homogeneous flow, with bubbles or droplets dispersed uniformly. Then, the gravity/buoyancy force becomes more dominant over inertia and surface tension because of the reduction of liquid velocity and the growth of bubbles. Consequently, bubbles migrate upwards while droplets fall downward, characterizing the separating region. After phase separation, the flow characteristics may still change for a certain distance before the flow is fully developed. Based on the observed flow regimes at various working conditions, a 3D flow pattern map is built, adding the distance from the expansion valve as the third dimension besides the mass flux and quality. In a following paper, the authors will discuss the effect of tube diameter, oil, and structure of expansion devices on developing two-phase flow. The developed flow patterns will be compared with the existing flow pattern map in steady conditions as an asymptote.

Investigating the Effect of Tube Diameter on the Performance of a Hybrid Photovoltaic-Thermal System Based on Phase Change Materials and Nanofluids.

The finite element (FEM) approach is used in this study to model the laminar flow of an eco-friendly nanofluid (NF) within three pipes in a solar system. A solar panel and a supporting phase change material (PCM) that three pipelines flowed through made up the solar system. An organic, eco-friendly PCM was employed. Several fins were used on the pipes, and the NF temperature and panel temperature were measured at different flow rates. To model the NF flow, a two-phase mixture was used. As a direct consequence of the flow rate being raised by a factor of two, the maximum temperature of the panel dropped by 1.85 °C, and the average temperature dropped by 1.82 °C. As the flow rate increased, the temperature of the output flow dropped by up to 2 °C. At flow rates ranging from low to medium to high, the PCM melted completely in a short amount of time; however, at high flow rates, a portion of the PCM remained non-melted surrounding the pipes. An increase in the NF flow rate had a variable effect on the heat transfer (HTR) coefficient.

Energy efficiency and power density analysis of a tube array liquid piston air compressor/expander for compressed air energy storage

To improve the power density and efficiency of compressed air energy storage (CAES), this paper adopts an array-based compression/expansion (C/E) chamber structure, coupling a liquid piston with a tubular heat exchanger to form a new compressor/expander. By providing a heat exchange chamber outside the arrayed C/E chamber, natural convection heat transfer is utilized and heat is absorbed during compression and released during expansion, constituting an advanced isothermal CAES system. For low-pressure (0.8 MPa to 5 MPa) and high-pressure (5 MPa to 31.25 MPa) stages, the effects of tube diameter and flow rate variations on C/E pressure, temperature, power density, and efficiency were analyzed. Results show that by keeping the tube diameter constant and the power density increasing one order of magnitude, the efficiency decreases about 9 %. Keeping the power density constant and reducing the tube diameter to 1/7 increases the efficiency of the low and high-pressure sections by about 16 % and 6.4 % respectively, or keeping the efficiency at 93.4 % and 83.9 %, increasing the power density all by about 50 times. This study provides a new way to improve the efficiency and power density of C/E by reducing the tube diameter of the array chamber for high-pressure and high-efficiency CAES.

Experimental study on the effect of tube diameter on gas–liquid wettability in silica microtubules

In this paper, the gas–liquid static contact angles in silica microtubes (inner diameter range of 5–700 μm) are measured by optical microscope. The experimental results show that the gas–liquid contact angles in the microtube have microscale wetting effect, which decrease monotonically with the decrease of the tube diameter and regularly deviate from the contact angle measured on the plate. When the tube diameter decreases from 700 μm to 5 μm, the contact angles of water and hexadecane decrease from 42.87° to 13.22° and 15.94°–9.09°, respectively. Actual microscale wetting effect causes the gas–liquid capillary force and driving resistance of residual droplets in pore-throat to be bigger than the value determined by the contact angle on the plate. The smaller the pore radius, the greater the influence of the microscale wetting effect on the capillary force. The larger pore-throat ratio and smaller throat radius, the greater influence of the microscale wetting effect on the driving resistance. These results advance our current understanding of wettability in porous media and offer us directly measured contact angles from pore scale which are better representation of actual pores than flat plate to characterize the fluid wettability in porous media.

Size and displacement combining detection on physics properties of carbon nanotubes using a proposed energy approach

In this paper, a coupling of advanced molecular structural model with energy method is developed to calculate the mechanical properties of single-walled carbon nanotubes (SWCNTs). The energy of a system is expressed by an advanced force field of molecular mechanics. Under the assumption of a small deformation and the principle of minimum potential energy, closed form formations are derived for temperature-dependent Young's modulus, Poisson's ratio, and bulk modulus, which are the functions of the length of C-C bonds and the out-plane displacement. The results show that the effects of tube diameter and out-plane displacement on the elastic properties of carbon nanotubes is significant when the tube diameter is small. Moreover, the principle of force-heat equivalent energy density (FHEED) is applied to describe the strain-dependent energy density of SWCNTs.

Effect of Tube Diameters and Functional Groups on Adsorption and Suspension Behaviors of Carbon Nanotubes in Presence of Humic Acid

The adsorption and suspension behaviors of carbon nanotubes (CNTs) in the water environment determine the geochemical cycle and ecological risk of CNTs and the compounds attached to them. In this study, CNTs were selected as the research object, and the effect of tube diameters and functional groups (multiwall CNTs (MWNTs) and hydroxylated MWNTs (HMWNTs)) on the adsorption and suspension behaviors of the CNTs in the presence of humic acid (HA) was systematically analyzed. The results indicate that HA adsorption decreased with the increase in the solution pH, and the adsorption amount and rate were negatively correlated with the tube diameter of the CNTs. The surface hydroxylation of the CNTs prevented the adsorption of HA, and the maximum adsorption amounts on the MWNTs and HMWNTs were 195.95 and 74.74 mg g−1, respectively. HA had an important effect on the suspension of the CNTs, especially for the surface hydroxylation, and the suspension of the CNTs increased with the increase in the tube diameter. The characteristics of the CNTs prior to and after adsorbing HA were characterized by transmission electron microscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. The results indicate that surface hydroxylation of the CNTs increased the adsorption of aromatic compounds, and that the CNTs with a smaller diameter and a larger specific surface area had a disordered carbon accumulation microstructure and many defects, where the adsorption of part of the HA would cover the defects on the CNTs’ surface. Density functional theory (DFT) calculations demonstrated that HA was more easily adsorbed on the CNTs without surface hydroxylation. This investigation is helpful in providing a theoretical basis for the scientific management of the production and application of CNTs, and the scientific assessment of their geochemical cycle and ecological risk.

NUMERICAL STUDY OF TUBE DIAMETER EFFECTS ON SOLIDIFICATION OF PCM IN A COMPACT HEAT EXCHANGER

NUMERICAL STUDY OF TUBE DIAMETER EFFECTS ON SOLIDIFICATION OF PCM IN A COMPACT HEAT EXCHANGER

Numerical simulation of the particle-wall collision strength and swirling effect on the performance of the axial flow cyclone separator

Abstract The axial cyclone separator has simple structure, operates to reducing dust concentration in grain storehouses, and features low production cost, and convenient installation. Aiming to obtain the separation characteristics of an axial flow guide separator, the particle wall collision and the performance of multi-tubes were simulated with Fluent. The renormalization group (RNG) k − ε model was used to study the turbulent modeling and the user define function (UDF) was used to calculate the particle-wall collision. The simulation and experimental results were compared to verify the computation model. The results showed that the basic feature of the flow pattern remains stable and the separation efficiency of 800 kg/m3 particles is higher than 2650 kg/m3 particles when the inlet velocity increases from 2 to 5 m/s. When the inlet velocity was 5 m/s, the normal velocity restitution ratio had a significant effect on the efficiency, the separation efficiency of 167 μm particles changed from 76.74 to 97.93% and a smaller normal velocity restitution ratio had a higher the efficiency. In comparison, the efficiency remained unchanged when changing the tangential velocity restitution ratio. Furthermore, the effects of three target wall materials on the separation efficiency were investigated. And the simulated efficiency the of 296 μm particle of 2024 aluminum, 410 stainless steel and Ga1–4V titanium were 82.15, 79.52 and 77.53% respectively. Besides, effects of tube diameter on performances of cyclone separator were discussed and high intense collisions between particles and walls may occur in a small diameter of cyclone tube, causing deteriorated separation performance. Moreover, with the addition of the dust chamber, the efficiency of cyclone used in combination is slightly improved since the vortex in the exhaust pipe has been finely changed.

Experimental study of air–steam condensation on the influence of tube diameter and inclination angle

Steam-air condensation is one of the important physical phenomena after reactor accidents, which has direct impacts on the discharge of containment residual heat after the accident. Previously, many researchers have proposed experimental correlations for condensation of non-condensable gas, which include the influence of pressure, concentration, and wall subcooling. However, there are relatively few studies on the influence of tube diameter and inclination angle. In order to investigate the heat transfer characteristics of the condenser at different tube diameters (19 mm, 15 mm, 12 mm) and inclination angles (0 ~ 90°), experiments were carried out in the pressure range of 0.15 ~ 1.6 MPa, air mass fraction of 14 ~ 87%, and wall subcooling of 28 ~ 122 °C. It shows that the condensation heat transfer coefficient (HTC) increases with the decrease of the tube diameter and inclination angle. The condensation HTC with a tube diameter of 12 mm and an inclination angle of 0°(Horizontally) is around 32 ~ 38% larger than that of the heat transfer tube with a tube diameter of 19 mm and an inclination angle of 90°(Vertically). Based on a total of 2276 data points from the present work and related experiments, an experimental correlation containing the effect of tube diameter and inclination angle is proposed, and its deviation is within ± 15% with 95% confidence.

PANAS GAS BUANG MESIN DIESEL UNTUK TAPIOKA

Drying technique plays a very important role in determining the quality and continuity of the tapioca flour manufacturing process. Traditionally the drying process is carried out by farmers by utilizing the sun's heat, but problems occur when the rainy season comes while production must continue to meet needs. which requires a large area of land and is very dependent on the weather with a lot of hot sun. Based on the analysis of the results of data processing using the Taguci experimental method to determine the optimum design of the main dimensions of the economizer in the laundry factory, the following conclusions are obtained. Effect of tube diameter, lay out, pitch ratio and excess area on the economizer Tube diameter (dO) has a significant effect on the amount tube and shell diameter (Ds).Picth ratio (PR) has a significant effect on shell diameter (Ds) but has no significant effect on the number of tubes. Excess area has a significant effect on the number of tubes but has no significant effect on shell diameter (Ds).Lay out has the same effect on shell diameter and tube number. Optimum economizer conditions. Optimum tube number ( Nt ) is obtained from a combination of tube diameter ( do ) 0.0254 m, excess area (PR) 1.2 , lay out 30o and pitch ratio 1 ,2. The optimum shell diameter is obtained from a combination of tube diameter (do) 0.0381 m, pitch ratio (PR) 1.2, excess area 1.2 and lay out 30o.Keywords: Dryer, Shell Diameter, Tube Diameter

Design aspects of forced circulation evaporators of high salty water from the view point of scale formation

In this paper, dryout phenomenon was studied for vertical tubes working at the operating condition of forced circulation evaporator in zero liquid discharge systems to find the maximum allowable value of temperature difference between evaporator effects in which scale formation and fouling do not occur. Eulerian two-fluid approach coupled with Rensselaer Polytechnic Institute wall boiling model was used to simulate upward flow subcooled boiling. Critical near-wall void fraction was used as the criterion of dryout. The value of the critical temperature difference was investigated for 36 cases. Values varied from 4.8 to 10.7 °C for different amounts of tube length, tube diameter and mass flux. In addition, the effect of tube length, tube diameter and mass flux on critical temperature difference was analyzed. The results showed that critical temperature difference decreased approximately linearly with an increase in tube length. Furthermore, the value of critical temperature difference decreased with the increase in tube diameter and decrease in mass flux and the effect of tube diameter is more significant at higher mass fluxes.