Constant Gas Flow Research Articles

Three-dimensional modeling of energy transport in a gliding arc discharge in argon

In this work we study energy transport in a gliding arc discharge with two diverging flat electrodes in argon gas at atmospheric pressure. The discharge is ignited at the shortest electrode gap and it is pushed downstream by a forced gas flow. The current values considered are relatively low and therefore a non-equilibrium plasma is produced. We consider two cases, i.e. with high and low discharge current (28 mA and 2.8 mA), and a constant gas flow of 10 l min−1, with a significant turbulent component to the velocity. The study presents an analysis of the various energy transport mechanisms responsible for the redistribution of Joule heating to the plasma species and the moving background gas. The objective of this work is to provide a general understanding of the role of the different energy transport mechanisms in arc formation and sustainment, which can be used to improve existing or new discharge designs. The work is based on a three-dimensional numerical model, combining a fluid plasma model, the shear stress transport Reynolds averaged Navier–Stokes turbulent gas flow model, and a model for gas thermal balance. The obtained results show that at higher current the discharge is constricted within a thin plasma column several hundred kelvin above room temperature, while in the low-current discharge the combination of intense convective cooling and low Joule heating prevents discharge contraction and the plasma column evolves to a static non-moving diffusive plasma, continuously cooled by the flowing gas. As a result, the energy transport in the two cases is determined by different mechanisms. At higher current and a constricted plasma column, the plasma column is cooled mainly by turbulent transport, while at low current and an unconstricted plasma, the major cooling mechanism is energy transport due to non-turbulent gas convection. In general, the study also demonstrates the importance of turbulent energy transport in redistributing the Joule heating in the arc and its significant role in arc cooling and the formation of the gas temperature profile. In general, the turbulent energy transport lowers the average gas temperature in the arc, thus allowing additional control of thermal non-equilibrium in the discharge.

A numerical study on flow patterns inside an electrical submersible pump (ESP) and comparison with visualization experiments

This paper presents a numerical study of flow pattern recognition inside the rotating impeller of an electrical submersible pump (ESP) using the transient multiphase Computational Fluid Dynamics (CFD) simulations. The calculation domain is constructed based on the previous experimental facility for visualizing flow patterns in an ESP (Barrios (2007)). The high-quality structured mesh comprising hexahedral grids is generated using multi-block technique in ANSYS ICEM. For CFD simulations, the realizable k-ε turbulence model with volume of fluid (VOF) and Eulerian-Eulerian multiphase models is successfully implemented in ANSYS Fluent solver. The sliding mesh technique is applied to interfaces where rotating and stationary parts interact. By incorporating the same boundary conditions as Barrios experimental study, three flow cases with constant gas flow rates and varying liquid flow rates are selected to conduct numerical simulations. The comparison of simulation results with Barrios’ observations shows that the Eulerian-Eulerian multiphase model is superior to VOF model for simulating gas-liquid two-phase flow in a rotating ESP. The single-phase simulation results match catalog curves, which validates the numerical methodology. For two-phase simulations, the simulated flow patterns using Eulerian-Eulerian model agree well with visualization experiments. Different flow patterns prevailing inside the rotating ESP impeller are captured. At low gas flow rate, bubbles are dispersed in liquid phase, and the flow pattern is categorized as dispersed bubble flow. As gas flow rate increases, bubbles can accumulate and coalesce, causing large gas-pocket formation leading to intermittent/slug flow. Transient multiphase CFD simulation is an efficient and reliable tool to predict flow patterns inside ESPs.

Design and construction of a proportional gas flow meter with application in Mössbauer spectroscopy

The design, construction and operation parameters of a gas flow proportional counter are presented in order to implement the integral conversion electron mossbauer spectroscopy technique (ICEMS). The detector works with the support of a multi-channel detection system and a source of highenergy radiation of 57Co. A constant gas flow of a mixture of 5% CH4 in He was used as a multiplier gas, which increased the signal intensity, and protected the sample´s surface of electric shocks. An internal filter for low energy X-rays was considered during the design to achieve a lower background noise and optimize the volume of gas consumed. With this built-in ICEMS detector it is feasible to characterize efficiently the magnetic properties and oxidation states (hyperfine interactions) of both bulk materials and thin films. The calibration of the device was performed by using an iron sample synthesized by powder metallurgy. It was successfully identified the presence of a distinctive sextet of the α-Fe phase with a hyperfine field of 330 kOe and an isomer shift of 0.312 mm / s. The great usefulness of the equipment was verified by solving the magnetic hyperfine interactions of the Mossbauer spectrum associated to a commercial stainless-steel washer.

The process intensification of CO2 absorption in Hilbert fractal reactor fabricated by a 3D printer

ABSTRACT CO2, as a major greenhouse gas, contributes greatly to the global warming. Increasing the efficiency of CO2 capture and utilization has becomea worldwide challenge. In the present research, Hilbert fractal reactor was fabricated via 3D printing technology for process intensification of ethanolamine (MEA) CO2 absorption. The performance of the Hilbert fractal reactor was investigated and compared to the serpentine reactor. For constant gas and liquid flow rates, the CO2 removal efficiency, the absorption rate, and the assumption of MEA increased with increasing concentration of MEA. In the comparison with the serpentine reactor, the CO2 removal efficiency in Hilbert fractal reactor is higher than that in the serpentine reactor at the relative low gas flow rate. The continuous bending in the Hilbert fractal reactor enhances the shear stress of the fluids, and the gas phase is segregated into the small bubbles which significantly increase the interface mass transfer. Under the relative high gas flow rate, the residence time of CO2 is short and the flow pattern in Hilbert reactor turns into the annular flow which adverse to CO2 absorption rate, and the advantage of Hilbert fractal reactor over serpentine reactor becomes negligible. The maximum CO2 removal efficiency of 57% was obtained in Hilbert fractal reactor.

Growth of Zn2GeO4 thin film by thermal evaporation on ITO substrate for thermoelectric power generation applications

In this paper, we have reported the growth of Zn2GeO4 thin film and investigated its potential for thermoelectric power generation applications. Zn2GeO4 alloy thin film was grown on Indium coated glass substrate by the evaporation of Zn and Ge metals with constant oxygen gas flow rate of 100 sccm in tube furnace. The grown film was cut into pieces and annealed at various temperatures from 500° to 700°C with a step of 100 °C in a programmable furnace for one hour. The structure of as grown and annealed thin films was verified by XRD and Raman spectroscopy measurements. The XRD data evident that Zn2GeO4 alloy hexagonal structure along with GeO2 and ZnO phases were observed at annealing temperatures 600 and 700 °C but below this temperature no alloy phase was detected by XRD and Raman Spectroscopy. To calculate the thermoelectric properties, temperature dependent Seebeck measurements were performed in the temperature range of 25–100 °C. It was observed that the value of Seebeck coefficient was increased from 91 to 847 μV/K as the annealing temperature increases from 500° to 700°C. This behavior was explained as; high temperature causes stress and cracks in the grown films which may induce electric and thermal discontinues at tips of cracks which cause high thermoelectric concentration. Scanning electron microscope images verified the development of cracks in the samples as annealing temperature increases. The behavior of Seebeck coefficient with the measurement temperature was also observed and explained in detail. The high value of Seebeck coefficient suggested that this material can be a potential candidate for thermoelectric power generation applications in near future.

Numerical simulation of gas-bubble formation through two submerged orifices

In this work, two-dimensional numerical simulations are carried out to analyse the dynamics of gas-bubble formation at two adjacent orifices submerged in an immiscible Newtonian liquid under the condition of constant gas flow rate using finite-volume-based commercial CFD solver Ansys Fluent. Two conditions for the ambient liquid are considered: firstly the liquid is in quiet condition and secondly, it is also co-flowing with the gas stream. The full cycle from the bubble formation to its detachment and the corresponding dynamics are simulated using the volume of fluid (VOF) method, which is one of the efficient front capturing techniques of Eulerian family. The study includes: (i) time sequence profile of bubble formation to clearly represent the bubble growth, neck formation and bubble break-up at a given Weber number (We), Reynolds number (Re), Bond number (Bo) and liquid to gas mean velocity ratio (Vr); (ii) bubble growth history for different Vr and at constant Re, We and Bo; (iii) effect of orifice spacing on bubbling synchronicity and frequency at given Vr, We, Re and Bo and (iv) synchronous bubbling regime, bubble size and formation time determination, bubble coalescence phenomenon and technique for its inhibition.

Experimental investigation into formation/dissociation characteristics of methane hydrate in consolidated sediments with resistance measurement

Natural gas hydrates (NGHs) are considered as a powerful potential energy resource. In this work, an experimental system containing a digital electrical bridge for resistance measurement was developed to gain an improved understanding of the formation/dissociation characteristics of NGHs in consolidated sediments. Using the apparatus, a dynamic methane hydrate formation method for sandstone cores was developed that can maintain a constant gas flow in the core during the methane hydrate formation process. As opposed to the traditional method that maintains a constant pressure in the core, higher resistance, permeability, and hydrate saturation for the core were obtained following methane hydrate formation equilibrium by using the proposed method. In order to investigate the methane hydrate formation characteristics in sandstone cores, the influences of core permeability, temperature, initial water saturation, and salinity on the resistance and hydrate saturation of two cores were analyzed in detail. The experimental results demonstrate that a relative lower temperature and higher initial water saturation in the core correspond to a higher hydrate saturation and water-to-hydrate conversation ratio. In the process of methane production from continent hydrate, the water output from the core with methane extraction was experimentally measured for the first time. It was found that, owing to the existence of free gas in the core holder, both the core resistance and methane production rate were not changed linearly with time. The methane production amount increased with an increase in initial water saturation, decrease in production pressure, or increase in pore volume in the core. It was demonstrated that water output is not a serious problem in the development of continental natural gas hydrate.

Scavenging effects of ascorbic acid and mannitol on hydroxyl radicals generated inside water by an atmospheric pressure plasma jet

In this study, we have studied the scavenging effects of radical scavengers (ascorbic acid and mannitol) on •OH radicals generated inside water by an atmospheric pressure plasma jet. Plasma was generated by using a sinusoidal power supply (applied voltage: 2.4 kV, frequency: 40 kHz) at a constant argon gas flow rate of 400 sccm and it was characterized by electrical and optical measurements. The technique of ultra-violet (UV) absorption spectroscopy was applied to investigate the effects of scavenging at 3, 6 and 9 mm depths below the water surface by using terephthalic acid as a •OH radical sensitive probe. Also, the effects of scavenging were studied by changing the concentration of radical scavengers and plasma exposure time. For both radical scavengers, the reduced concentrations of •OH radicals were found to decrease with increasing depths as their production would also be reduced by decreasing intensities of plasma-initiated UVs with increasing depths. The effectiveness of ascorbic acid on the scavenging of •OH radicals appeared much stronger than mannitol at all depths inside water since the deprotonated form of ascorbic acid consumes two •OH radicals whereas mannitol consumes only one. Also, the reduced concentration of OH radicals with addition of scavengers was found to be increased under longer plasma exposure time even though the generation of OH radicals were also increased. The detailed mechanism on the formation of •OH radicals inside water has been discussed along with the causes of scavenging. These results can be an important milestone in the applications of non-thermal plasma sources requiring the reduction of •OH radicals.

Modeling of glow discharge in longitudinal gas flow in a plane channel of variable cross section

A two-dimensional model of glow discharge positive column in gas flow has been suggested in this paper. It is considered that the discharge maintained between the permeable mesh electrodes installed in the initial and end sections of the plane channel. In general case the channel width changing along the stream is accounted. The positive column in gas flow is described by integro-differential system of equations with an approximation of constant gas flow density. The border conditions for gas ionization degree and temperature in the initial section of channel are given by any functions. An analytical solution of that system was obtained and special cases of the boundary conditions analyzed.

The Esophageal Manometry with Gas-perfused Catheters.

BackgroundThe well-established methods for esophageal manometry have some disadvantages: the-water-perfused catheters needs calibration by gravity and measuring in supine position, and the solid-state catheters are very expensive. Manometry using gas-perfused catheters is a suitable alternative. There have been only a few publications about this.Objectives and methodsThe results for esophageal manometry in 1700 patients were retrospectively analyzed based on the clinical reports and the manometry data. The gas-perfusion manometry was critically assessed.ResultsThe mean age was 54 years. The indications for esophageal manometry were GER symptoms in 58.5% (pathological DeMeester score in 41.8%), dysphagia in 12.4%, and already known achalasia in 8.9%. Motility disorders could be found in 40% of the patients with GER symptoms (51% of the patients with pathological DeMeester score), and in 88% of achalasia patients. The resting LES pressure was 8.9±5.94 mmHg with GER symptoms, 16.4±12.79 mmHg without GER symptoms, and 26.8±14.03 mmHg with achalasia. The relaxation LES pressure was 20.0±10.93 mmHg in achalasia patients, and 8.3±5.77 mmHg in the others.The gas-perfusion manometry was well tolerated by all patients without any serious complications.DiscussionManometry using gas-perfused catheters is an easy to handle and inexpensive method to investigate the esophageal motility. The suitability of gas perfusion with helium for esophageal manometry depends on physical and technical requirements, such as a constant gas flow, a dead space in the transducer, and the catheter being as small as possible. In consideration of this, the detection of the pressure changing in swallowing acts is excellent. The measured LES pressures are generally lower than with other methods like with water-perfused or solid-state catheters, possibly because of the higher compliance in a gas-filled surrounding. The normal values in gas-perfusion manometry are comparable but not identical with the values of other manometric methods.

The effect of air stable n-doping through mild plasma on the mechanical property of WSe2 layers

Two-dimensional transition metal dichalcogenides have been widely applied to electronic and optoelectronic device owing to their remarkable material properties. Many studies present the platform for regulating the contact resistance via various doping schemes. Here, we report the alteration of mechanical properties of few top layers of the WSe2 flake which are processed by air stable n-doping of N2O with a constant gas flow through mild plasma and present better manufacturability and friability. The single-line nanoscratching experiments on the WSe2 flakes with different doping time reveal that the manufacturable depths are positively correlated with the exposure time at a certain range and tend to be stable afterwards. Meanwhile, material characterization by x-ray photoelectron spectroscopy confirms that the alteration of mechanical properties is owing to the creation of Se vacancies and substitution of O atoms, which breaks the primary molecular structure of the WSe2 flakes. The synchronous Kelvin probe force microscopy and topography results of ROI nanoscratching of a stepped WSe2 sample confirmed that the depth of the degenerate doping is five layers, which was consistent with the single-line scratching experiments. Our results reveal the interrelationship of the mechanical property, chemical bonds and work function changes of the doped WSe2 flakes.

Evaluating combustion, performance and emission characteristics of diesel engine using karanja oil methyl ester biodiesel blends enriched with HHO gas

With a specific end goal to take care of the worldwide demand for energy, a broad research is done to create alternative and cost effective fuel. The fundamental goal of this examination is to investigate the combustion, performance and emission characteristics of diesel engine using biodiesel blends enriched with HHO gas. The biodiesel blends are gotten by blending KOME obtained from transesterification of karanja oil in various proportions with neat diesel. The HHO gas is produced by the electrolysis of water in the presence of sodium bicarbonate electrolyte. The constant flow of HHO gas accompanied with biodiesel guarantees lessened brake specific fuel consumption by 2.41% at no load and 17.53% at full load with increased the brake thermal efficiency by 2.61% at no load and 21.67% at full load contrasted with neat diesel operation. Noteworthy decline in unburned hydrocarbon, carbon monoxide, carbon-dioxide emissions and particulate matter with the exception of NOx discharge is encountered. The addition of EGR controls this hike in NOx with a slight decline in the performance characteristics. It is clear that the addition of HHO gas with biodiesel blends along with EGR in the test engine improved the overall characterization of engine.

Absorption of CO2 from modified flue gases of power generation Tarahan chemically using NaOH and Na2CO3 and biologically using microalgae

This research was carried out on the absorption of CO2 from the modified flue gases of power generation Tarahan using NaOH (sodium hydroxide) and Na2CO3 (sodium carbonate). The operation was conducted in a packed column absorber and then the output gases from the packed column was fed into photo-bioreactor for biological absorption. In the photo-bioreactor, two species of microalgae, N. occulata and T. chuii, were cultivated to both absorb CO2 gas and to produce biomass for algal oil. The aims of this research were, first, to determine the effect of absorbent flow rate on the reduction of CO2 and on the decrease of output gas temperature, second, to determine the characteristics of methyl ester obtained from biological absorption process. Flow rates of the absorbent were varied as 1, 2, and 3 l/min. The concentrations of NaOH and Na2CO3 were 1 M at a constant gas flow rate of 6 l/min. The output concentrations of CO2 from the absorber was analyzed using Gas Chromatography 2014-AT SHIMADZU Corp 08128. The results show that both of the absorbents give different trends. From the absorption using NaOH, it can be concluded that the higher the flow rate, the higher the absorption rate obtained. The highest flow rate achieved maximum absorption of 100%. On the other hand, absorption with Na2CO3 revealed the opposite trend where the higher the flow rates the lower the absorption rate. The highest absorption using Na2CO3 was obtained with the lowest flow rate, 1 l/min, that was 45,5%. As the effect of flow rate on output gas temperature, the temperature decreased with increasing flow rates for both absorbents. The output gas temperature for NaOH and Na2CO3 were consecutively 35 °C and 31 °C with inlet gas temperature of 50°C. Absorption of CO2 biologically resulted a reduction of CO2 up to 60% from the input gas concentration. Algal oil was extracted with mixed hexane and chloroform to obtain algal oil. Extracted oil was transesterified to methyl ester using sodium hydroxide as a catalyst. The results of in-situ transesterification method cannot be identified. Both microalgae achieved maximum yield at 2% catalyst concentration. Nannochloropsis occulata achieved the highest yield of algal oil that is 88.5%. The highest content of methyl ester from Nannochloropsis occulata was undecanoic acid methyl ester by 55.42% and the result from Tetraselmis chuii was palmitic acid methyl ester by 81.58%.

An Alternate Approach to Friction Factor Computations Based on Entropy Generation in Gas Micro Flows

The gas micro flows are deployed in heat-sinks of many practical micro devices, and cooling systems for gas turbine blades etc. In present study, fluid friction characteristics of laminar micro flow, operating at low Reynolds number, are studied. This flow model is representative of fluid flows in many micro device applications. Fanning friction factor computations were re-modeled using ‘entropy generation’ and ‘axial temperature rise’ in the flow domain. Entropy generation considerations and adiabatic wall boundary condition isolate viscous dissipation effects from other causes of heating. Navier-Stoke and energy equations were numerically solved for constant properties gas (air) flow in circular micro pipe using ANSYS/FLUENT® software and post processing in C++. The results of present study show good agreement with the well established classical Hagen-Poiseuille correlations, experimentally validated methods of Morini, and Celata et al. Present method is useful where the laboratory facilities for micro flow experiments are not available.

Quantification of Carbon Dioxide Removal at Low Sweep Gas and Blood Flows

Advancement in oxygenator membrane technology has further expanded the boundaries in the clinical application of extracorporeal carbon dioxide removal (ECCO2R). Despite the advent of modern poly-4-methyl-1-pentene (PMP) membranes, limited information exists on the performance of these membranes at low sweep gas and blood flows. Moreover, physiological relationships for CO2 removal at these flows are less explored. Hence, CO2 removal was quantified in an in vitro setting using a PMP membrane oxygenator. ECCO2R was performed using a .8 m2 surface pediatric oxygenator in an in vitro setting with freshly drawn single-source porcine blood. In this setting, low blood flows of either 200 or 350 mL/min were generated, with sweep gas flow rates of 100, 200, and 400 mL/min, respectively. CO2 transfer ranged from 14.05 ± 4.35 mL/min/m2 to 18.76 ± 4.26 mL/min/m2 at a sweep gas to a blood flow ratio of .5:1 to 2:1 (p < .01). Decreasing this ratio i.e., increasing the blood flow (.5:1.75 and 2:1.75) resulted in a lower CO2 transfer of 10.00 ± 4.77 mL/min/m2 to 16.87 ± 5.09 mL/min/m2, which was still statistically significant (p < .01). Alternatively, decreasing the sweep gas to blood flow ratio, while maintaining a constant gas flow, did not show a significant increase in CO2 extraction (p > .05). At these test parameters, an increase in sweep gas improved the CO2 transfer, whereas an increase in blood flow resulted in a lower CO2 transfer. These results indicate that CO2 removal in low-flow ECCO2R is mainly sweep gas flow driven. Although these settings might not be applicable for clinical use, this study gives tangible information about the important factor involved in ECCO2R.

Effect of Cold Atmospheric Plasma on Inactivation of Escherichia coli and Physicochemical Properties of Apple, Orange, Tomato Juices, and Sour Cherry Nectar

In this study, orange, tomato, apple juices, and sour cherry nectar were exposed to an atmospheric pressure plasma jet. Plasma treatments were carried out using air as a precursor under constant gas flow (3000 L/h) at 650 W for different treatment times (30, 60, 90, and 120 s). After plasma processing, reduction of Escherichia coli, Hunter’s color parameters (L*, a*, b*), total phenolic content, and pH values were evaluated. The inactivation effect of cold atmospheric plasma (CAP) was investigated on E. coli, and the highest significant reductions were achieved in apple juice (4.02 ± 0.03 log CFU/mL) followed by sour cherry (3.34 ± 0.09 log CFU/mL), while the values in orange (1.59 ± 0.17 log CFU/mL) and tomato juices (1.43 ± 0.22 log CFU/mL) were lower, which could be attributed to the food matrix. Color parameters, except for apple juice, did not show significant changes after processing. Compared to untreated juice, plasma treatment yielded higher phenolic content from 10 to 15%, while pH values did not change significantly and the temperature remained below 40 °C after all plasma treatments. This study showed that CAP treatment had positive influences on phenolic stability and color change in all samples regardless of food intrinsic factors, while it was more effective on bacterial inactivation in clear juices than turbid ones. Our results indicate that atmospheric plasma appears to be a promising technology for microbial inactivation without causing undesirable changes in food product.

Growth of ZnO Nanowires by Vapour Solid Mechanism

The growth of zinc oxide nanowires is further investigated by thermal evaporation method and is discussed with respect to vapour-solid (V-S) growth mechanism. In this paper, ZnO nanowires were synthesized on glass substrate without the use of any catalyst with a constant flow of argon gas 1.36 psig and oxygen gas of 0.34 psig. Zinc powder of 99.99% purity is placed in a horizontal furnace and exposed to temperature of 600°C for 90 minutes. The surface morphology of the deposited zinc oxide is investigated by the atomic force microscopy (AFM) images and it was found that the deposited ZnO has a rough surface while field-emission scanning electron microscopy (FESEM) confirms the morphology of the ZnO nanowires. Photoluminescence (PL) spectra indicate that the optical quality of the deposited structure is potentially excellent with high energy excitonic emission close to the band edge which is assigned to the surface exciton in ZnO at 3.4eV.

Improving the Tribological and Mechanical Properties of an Aluminium Substrate by Deposition of TiCN Coatings

The article presents an investigation of the influence of coating deposition parameters, in particular a variation with 50% of both cathodic arc current and bias voltage, on the mechanical and tribological properties of TiCN coatings on an aluminium substrate deposited by the cathodic arc evaporation of metals at a constant gas flow ratio between C2H2 and N2 of 17.65 % / 82.35 %. The determined nanohardness values for the samples examined are in the range of 10 to 23 GPa. Surface morphology and chemical composition were estimated by a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) of SEM. The tribological behaviour of the TiCN layers was examined using the Ball-on-Disk method (ASTM G99-95) and using a ball made of Al2O3 as a counter-part and a load of 10N. The friction coefficient was measured in the range of 0.182 to 0.116.

The mechanism of plasma plume termination for pulse-excited plasmas in a quartz tube

Although the formation and propagation of plasma plume for atmospheric pressure plasmas have been intensively studied, how does the plasma plume terminate is still little known. In this letter, helium plasma plumes are generated in a long quartz tube by pulsed voltages and a constant gas flow. The voltages have a variable pulse width (PW) from 0.5 μs to 200 μs. It is found that the plasma plume terminates right after the falling edge of each voltage pulse when PW < 20 μs, whereas it terminates before the falling edge. When PW is larger than 30 μs, the duration of plasma plume starts to decrease, and the termination is found to occur at the current zero moment of the discharge current through the high-voltage electrode, which is much different from that through the ground electrode. This indicates that part of the discharge current is shunted by the plasma plume to its downstream gas region. An equivalent circuit model is developed, from which the surface charge deposited on the quartz tube is found crucial for accelerating the termination of a plasma plume when PW > 30 μs.

Micro-CT imaging of live insects using carbon dioxide gas-induced hypoxia as anesthetic with minimal impact on certain subsequent life history traits

BackgroundLive imaging of whole invertebrates can be accomplished with X-ray micro-computed tomography (micro-CT) at 10-100 μm spatial resolution. However, image quality could be compromised by the movement of live subjects, producing image artefacts. We tested the feasibility of using CO2 gas to induce temporary full-immobilization of sufficient duration to image live insects based on their ability to tolerate hypoxic conditions. Additionally, we investigated the effects of these prolonged hypoxic conditions on several life history traits of a lepidopteran species.MethodsLive Colorado potato beetle (CPB) and true armyworm (TAW) adults were immobilized under a constant CO2 gas flow (0.5 L/min), and scanned using micro-CT (80 kVp; 450 μA). An L8 (24) orthogonal array (OA) was used to evaluate the effects of prolonged CO2-induced anesthesia on the recovery, longevity, and incidence of mating of TAW adults. The variable factors were age (immature and mature), sex (female and male), exposure time (3 and 7 h), and exposure regime (single and repeated).ResultsWith this method, successful 3D reconstruction and visualizations of CPB and TAW adults were produced at 20 micron voxel spacing at an acceptable radiation dose and image noise level. From the inverse-square relationship found between the radiation doses and image noise levels, the optimal scanning protocol produced an entrance dose of 6.2 ± 0.04 Gy with images of 129.6 ± 5.1 HU noise level during a 2.7 h scan.Independent OA experiments indicated that CO2 gas did not result in death of exposed TAW adults, except when older males were exposed for longer durations. Exposure time and sex were more influential factors affecting recovery, longevity, and mating success than age and exposure regime following CO2 exposure.ConclusionWe have demonstrated that using CO2 gas during micro-CT imaging effectively induces safe, repeatable, whole-body, and temporary immobilization of live insects for 3D visualizations without motion artefacts. Moreover, we have shown that exposed TAW individuals made a full recovery with very little impact on subsequent longevity, and mating success post hypoxia. This method is applicable to other imaging modalities and could be used for routine exploratory and time-course studies, for repeated scanning of live and intact individuals.