Dual Gas Research Articles

Large eddy simulations of turbulent combustion of kerosene-air in a dual swirl gas turbine model combustor at high pressures

In advanced gas turbine engines, high-pressure combustion generally occurs with combustion chamber pressure exceeding the critical pressure of the engine fuel. In this paper, large eddy simulations are conducted in a dual swirl gas turbine model combustor to analyze the effects of different fuel-air equivalence ratios and chamber pressures on swirling injection and turbulent combustion. Numerical results reveal that intricate interactions exist between swirling flows and high-pressure turbulent flame. Strong swirling injection of air could cause reverse flows in the inner injector, which lead to a V shaped partially premixed turbulent flame at a chamber pressure of 3 MPa. As the operating pressure increases to 5 MPa, decreased injection velocity would prevent reverse flows in the inner injector, leading to the turbulent diffusive flame. On the other hand, combustion causes flow acceleration, gaseous expansion, and strong thermophysical property variations, which would influence the reverse flows, increase the expansion angle in swirling injection, and dictate the size of central recirculation zone and the oscillation frequency of precessing vortex core. Results obtained herein would help gain fundamental understanding on high-pressure swirling flows and flame dynamics in advanced gas turbine engines.

Antiresonant Hollow-Core Fiber-Based Dual Gas Sensor for Detection of Methane and Carbon Dioxide in the Near- and Mid-Infrared Regions.

In this work, we present for the first time a laser-based dual gas sensor utilizing a silica-based Antiresonant Hollow-Core Fiber (ARHCF) operating in the Near- and Mid-Infrared spectral region. A 1-m-long fiber with an 84-µm diameter air-core was implemented as a low-volume absorption cell in a sensor configuration utilizing the simple and well-known Wavelength Modulation Spectroscopy (WMS) method. The fiber was filled with a mixture of methane (CH4) and carbon dioxide (CO2), and a simultaneous detection of both gases was demonstrated targeting their transitions at 3.334 µm and 1.574 µm, respectively. Due to excellent guidance properties of the fiber and low background noise, the proposed sensor reached a detection limit down to 24 parts-per-billion by volume for CH4 and 144 parts-per-million by volume for CO2. The obtained results confirm the suitability of ARHCF for efficient use in gas sensing applications for over a broad spectral range. Thanks to the demonstrated low loss, such fibers with lengths of over one meter can be used for increasing the laser-gas molecules interaction path, substituting bulk optics-based multipass cells, while delivering required flexibility, compactness, reliability and enhancement in the sensor’s sensitivity.

Performance Enhancement of Nitrogen Dual Expander and Single Mixed Refrigerant LNG Processes Using Jaya Optimization Approach

The nitrogen (N2) expander and single mixed refrigerant (SMR) liquefaction processes are recognized as the most favorable options to produce liquefied natural gas (LNG) at small-scale and offshore sites. These processes have a simple and compact design that make them efficient with respect to their capital costs. Nevertheless, huge operating costs, mainly due to their lower energy efficiency, remains an ongoing issue. Utilization of design variables having non-optimal values is the primary cause for the lower energy efficiency; which, in turn, leads to exergy destruction (i.e., entropy generation), and ultimately the overall energy consumption is increased. The optimal execution of the design variables of LNG processes can be obtained through effective design optimization. However, the complex and highly non-linear interactions between design variables (refrigerant flowrates and operating pressures) and objective function (overall energy consumption) make the design optimization a difficult and challenging task. In this context, this study examines a new optimization algorithm, named “Jaya”, to reduce the operating costs of nitrogen dual expander and SMR LNG processes. The Jaya approach is an algorithm-specific parameter-less optimization methodology. It was found that by using the Jaya algorithm, the energy efficiency of the SMR process and nitrogen dual expander natural gas (NG) liquefaction process can be enhanced up to 14.3% and 11.6%, respectively, as compared to their respective base cases. Using the Jaya approach, significant improved results were observed even compared to other previously used optimization approaches for design optimization. Results of conventional exergy analysis revealed that the exergy destruction of SMR and N2 dual expander process can be reduced by 17.4% and 14%, respectively. Moreover, economic analysis identified the 13.3% and 11.6% relative operating costs savings for SMR and N2 dual expander LNG processes, respectively.

Stability analysis of integral load-bearing structure of surrounding rock of gob-side entry retention with flexible concrete formwork

According to the factors affecting the stability of the integral load-bearing structure of the surrounding rock of a retained gob-side entry, the load-bearing capacity of roadside supports with flexible concrete formwork is studied to propose a new integrated supporting control technology. This approach is based on a bolt and anchor cable support with a wire mesh for retaining the surrounding rock of a roadway. Moreover, the core of this technology involves roof bolts and steel beam supports with a steel–plastic wire mesh on the side of the gob beside the retained roadway, combined with the strengthening support of dual single props with upper and lower crossbars in the roadway. The roof-strata pre-stressed anchorage composite load-bearing structure, roadside flexible concrete formwork load-bearing structure, wire-mesh wall structure, solid coal wall load-bearing structure, and four-in-one load-bearing and stress-transferring control device in the retained roadway are formed in the surrounding rock of the retained roadway using integrated supporting control technology. Additionally, their supporting mechanisms are analyzed, and the corresponding construction technologies are clarified. Practical field results indicate that the integral load-bearing structure of the surrounding rock of the retained roadway formed by the integrated supporting control technology effectively controls the deformation and destruction of the surrounding rock, ensuring the success of the retaining roadway. Furthermore, dual gas channels are successfully constructed using this technology, thereby validating its efficient gas extraction.

Effect of methanethiol on process performance, selectivity and diversity of sulfur-oxidizing bacteria in a dual bioreactor gas biodesulfurization system

This study provides important new insights on how to achieve high sulfur selectivities and stable gas biodesulfurization process operation in the presence of both methanethiol and H2S in the feed gas. On the basis of previous research, we hypothesized that a dual bioreactor lineup (with an added anaerobic bioreactor) would favor sulfur-oxidizing bacteria (SOB) that yield a higher sulfur selectivity. Therefore, the focus of the present study was to enrich thiol-resistant SOB that can withstand methanethiol, the most prevalent and toxic thiol in sulfur-containing industrial off gases. In addition, the effect of process conditions on the SOB population dynamics was investigated. The results confirmed that thiol-resistant SOB became dominant with a concomitant increase of the sulfur selectivity from 75 mol% to 90 mol% at a loading rate of 2 mM S methanethiol day−1. The abundant SOB in the inoculum – Thioalkalivibrio sulfidiphilus – was first outcompeted by Alkalilimnicola ehrlichii after which Thioalkalibacter halophilus eventually became the most abundant species. Furthermore, we found that the actual electron donor in our lab-scale biodesulfurization system was polysulfide, and not the primarily supplied sulfide.

Reducing relative response factor variation using a multidetector approach for extractables and leachables (E&L) analysis to mitigate the need for uncertainty factors

Characterization of Extractables and Leachables (E&Ls) is an important aspect of product quality in important fields such as pharmaceuticals, medical devices and food contact materials. The main goal of an E&L study is identification and quantification of those species which may leach from packaging materials used to contain pharmaceuticals or which may leach directly out of a medical device or food contact material and thus may result in patient exposure. It is common practice to perform relative quantitation of extractables and leachables using surrogate standards due to the large diversity of species observed and the lack of available reference standards. A key problem in obtaining accurate E&L results arises due to response factor (RF) variation. Different compounds at the same concentration give different signal intensities and thus have different RF values. Two key aspects of study quality are affected by this problem. First, the evaluation of the number of compounds which are above the toxicologically relevant threshold (analytical evaluation threshold, (AET)) can be affected (RF Problem 1: AET Underreporting). Second, quantitative accuracy is affected which can reduce the reliability of the margin of safety (MOS) calculations which serves as the basis of the toxicological evaluation (RF Problem 2: Quantitative Error). RF databases have been the main solution proposed for solving these problems but do not reduce the underlying RF variation and lack the scope required to address quantitative error for compounds not contained in the database. In the absence of other solutions, large uncertainty factors (UF) have been applied in the AET calculations to account for RF Problem 1: AET Underreporting. These UF factors have been assigned values of 4 for GCMS and up to 10 for LCMS. Large uncertainty factors have a number of unintended negative consequences including the need for large amounts of sample concentration (>10X) prior to analysis resulting in potential compound loss or degradation and increased matrix effects. To overcome these problems, this publication demonstrates a multidetector approach using an HPLC system coupled with a Quadrupole Time of Flight Liquid Chromatography Mass Spectrometer (QTOF-LCMS), Charged Aerosol Detector (CAD) and an Ultraviolet-Visible Detector (UV) and a dual detection Gas Chromatography Mass Spectrometry (GCMS) system using a Polyarc Reactor system with Flame Ionization Detection (FID). Herein, it is demonstrated that this combination of methods (the multidetector approach) allowed detection and accurate surrogate standard quantitation of 217 unique extractables spanning a wide range of chemical properties (Mw, logP, pKa and boiling point). The combination of optimized detector selection with appropriate standard selection was verified to provide positive detection for 94% of the compounds at the AET level and a high level of quantitative accuracy (± 20% for 85% of the compounds and ±40% for 91% of the compounds) while using only a UF of 2. Unlike the RF database approach, the multidetector approach is not limited to only those compounds contained in the database but is applicable to the majority of extractables.

Transdermal Alcohol Monitoring with a Printed Amperometric Gas Sensor

Introduction We report development of a prototype transdermal ethanol (EtOH) monitor, in wristwatch format, to provide a modern device for consumer, clinical and law enforcement applications. Our vision is an attractive, comfortable smart watch, which will measure transdermal alcohol concentration (TAC) and predict blood alcohol concentration (BAC) during drinking. Current commercially available alcohol monitors are bulky, ankle-fixed devices, predominantly used in court-ordered monitoring and some research studies [1]. There has been little advancement in wearability, comfort and analytical performance of these devices. Our long-term goal is to realize a new generation of wearable monitor that combines a sensitive ethanol measurement and smartwatch capabilities in a comfortable and attractive package. This device could greatly expand the possible applications employing this technology. Experimental Watch Fabrication. The sensor platform was fabricated based on a scaled down version of our dual gas sensor platform and printed amperometric gas sensor [2, 3]. The simple prototype device contains a single EtOH sensor, analog front end, 24 bit ADC, Bluetooth LE chip and T/P/RH sensor. The board is contained in a commercially available wristwatch enclosure (BodyCase B1606117) as in Fig. 1. Initial tests of linearity and S/N showed that the circuit was linear over at least 0-300 ppm EtOH at 25 C (R2 = 0.9996 – 0.9998 for 4 boards) with sensitivity 23 ± 2 nA/ppm (for 4 boards) and limit of detection (LOD) 0.26 ± 0.06 ppm.Laboratory Testing. A flow cell was designed to deliver 0 – 0.4 w/o EtOH (simulated BAC) through a Strat-M membrane, which served as a skin surrogate [4]. EtOH solutions in phosphate buffered saline pH 7.1 were used. The cell was configured such that EtOH permeated the Strat-M, with vapor entering the headspace above to which the watch was interfaced. Results and Conclusions Flow Cell Tests. EtOH steps between 0 and 0.4 %EtOH (simulated BAC) were applied with 30 min exposure at each step. A 6 hr stability test was included. High stability and S/N were demonstrated. The EtOH concentrations in simulated BAC solutions were standardized and calibrated to headspace vapor phase concentrations, giving a calibration curve for %EtOH in the PBS buffer (simulated %BAC) as a function of measured EtOH (ppm EtOH) in headspace above the membrane. For two devices, we obtained highly linear calibrations (R2 = 0.9983, 0.9992, respectively) with slope of 0.0013% and 0.0011% BAC/ppm EtOH, with near zero intercepts (-0.009 and -0.006 %BAC, respectively). From these two tests and the baseline noise we determined a limit of detection (LOD) of ±0.005% BAC. In later tests (e.g., Fig. 2) the LOD was considerably improved. The 6 hr stability test at 0.12% EtOH showed very stable output of 0.116 ±0.003 % EtOH.Human Tests. An example of real transdermal alcohol measurement using the watch prototype on a human subject is shown in Fig. 2. A male volunteer ingested six 6 oz. aliquots of 5 v/o alcoholic beverage over ca. 1 hr. Two different watches were used, one fixed to each wrist. The measured temperature at the devices was typically in the range 28 – 34 C during tests. The data in Fig. 2 are not temperature compensated. A commercial BACtrack Trace breathalyzer was used to collect contemporaneous breath alcohol data (BrAC).The TAC measurements taken on two wrists correlated quite well with each other. The TAC values tracked BrAC trend qualitatively, but with a shift to longer times, with the peak BrAC occurring ca. 1.5 hours before the peak TAC value. In other tests we have also observed lags on the order 30 min to 2 hr for TAC vs. BrAC measures. This lag is well-known for transdermal ethanol measurements [5] and presents a challenge for reliable instantaneous BAC prediction from TAC data. We note that the lag can depend on many factors including person-to-person variability of skin permeability, presence of sweat (humidity), food consumption and variable rates of alcohol consumption and metabolism, to name a few examples. Mechanical effects such as sudden movements and impacts can also affect the measurement.We demonstrated use of a printed amperometric sensor for TAC measurement. Controlled clinical trials are currently being performed in collaboration with Boston Medical Center. The ultimate goal is to reliably predict BAC from TAC data across a broad range of individuals and use cases.

Study on dynamic characteristics of micro gas turbine with load mutation of pulse generator

Because of the sudden load phenomenon of the pulse generator, it is required that the gas turbine, as the primary energy source of the pulse generator, not only has certain stability, but also has good dynamic performance. In this paper, based on AMESim, the dual rotor micro gas turbine pulse generator set is modeled, calculated and studied the dynamic characteristics of the micro gas turbine in the case of sudden change of fuel quantity, and the effects of fuel increasing speed on the dynamic characteristics of gas turbine are studied with three different fuel supply strategies (a), (b) and (c).

Numerical Simulation of the Behavior of Hydrogen Source in a Novel Welding Process to Reduce Diffusible Hydrogen

This study aims to reduce the diffusible hydrogen content in deposited metal during gas metal arc welding (GMAW) and flux-cored arc welding (FCAW) which induces cold cracking. To achieve this, a novel welding torch with a dual gas nozzle has been developed. This special welding torch decreases the hydrogen source gas evaporated from a welding wire by the suction from the inner gas nozzle. In order to improve the suction efficiency of this evaporated gas, precise control of the suction gas flow is indispensable. In this paper, a simplified numerical simulation model of this process has been described. This model can take account of the evaporation of the hydrogen source gas from the wire while simulating the behavior of the shielding gas and the arc. Using this model, the effect of suction nozzle structure and torch operating conditions on suction gas flow pattern and suction efficiency was also investigated to understand the process mechanism. Furthermore, the diffusible hydrogen content in deposited metal was measured by chromatography as a validation step. Results show that some of the shielding gas introduced from a shielding nozzle was drawn inward and also branched into an upward flow that was sucked into the suction nozzle and a downward flow to a base metal. This branching height was defined as the suction limit height, which decisively governed the suction efficiency. As a result, in order to reduce the diffusible hydrogen, it was suggested that the suction limit height should be controlled towards below the wire position, where the evaporation rate of the hydrogen source gas peaks through optimization of the suction nozzle design and the torch operating conditions.

Strain-induced novel properties of alloy nitride nanotubes

Nanotubes have become the focus of interest in recent years because of their unique properties that make them natural candidates for many devices. The junction of two different nanotubes can form alloys imparting new properties or enhance existing properties associated with one or both starting materials. The present study aims to investigate the properties of aluminum and gallium nitride (AlN and GaN, respectively) single- and double-walled nanotubes and double-walled alloy nanotubes (Al0.5Ga0.5N and Ga0.5Al0.5N) by using the density functional theory (DFT). It is observed that the emission of single-walled nanotubes (SWNT) changes from deep-UV to the blue region of the electromagnetic spectrum for double-walled GaN nanotubes (DWGaN). For the alloy nanotubes, the emission occurs at UVA and UVB regions for Al0.5Ga0.5N and Ga0.5Al0.5N, respectively. Also, the impact of the applied mechanical strain is investigated for all nanotubes. It is observed that with tensile strain, the band gap energy decreases while the piezoelectricity increases. Of all the zigzag nanotubes investigated, SWAlN, DWAlN, and the Al0.5Ga0.5N alloy nanotube exhibit larger piezoelectric constants. The analysis of electron density revels that the alloy nanotubes can be used to fabricate a selective dual gas sensor and that the functionalization, using an interface or by the application of strain, can be used to modulate the properties of materials.

Review on Application of Quaternary Ammonium Salts for Gas Hydrate Inhibition

Gas hydrate solids occurrence is considered as one of the serious challenges in flow assurance as it affects the hydrocarbon production significantly, especially in deep water gas fields. The most cost-effective method to inhibit the formation of hydrate in pipelines is by injecting a hydrate inhibitor agent. Continuous studies have led to a comprehensive understanding on the use of low dosage hydrate inhibitors such as ionic liquid and quaternary ammonium salts which are also known as dual function gas hydrate inhibitors. This paper covers the latest types of quaternary ammonium salts (2020–2016) and a summary of findings which are essential for future studies. Reviews on the effects of length of ionic liquids alkyl chain, average suppression temperatures, hydrate dissociation enthalpies, and electrical conductivity to the effectiveness of the quaternary ammonium salts as gas hydrate inhibitors are included.

Investigation of the Impact Factors on the Optimal Intermediate Temperature in a Dual Transcritical CO2 System with a Dedicated Transcritical CO2 Subcooler

As a natural fluid with superior environment advantages, CO2 is used to constitute a dual transcritical system to reduce performance deterioration under high gas-cooler outlet temperature. Aiming at the system configuration, improvement potential, and optimization, the proposed system is deeply analyzed, and corresponding coupling models are presented in detail. First, the veracity of simulation models is completely verified by comparing with previous measurements. Then, the existence of the optimal intermediate temperature is validated, while the optimal values are found to increase with the augmentation in ambient and water-feed temperatures. Moreover, the negative effects of the pinch point on the heat transfer inside the gas cooler could be greatly reduced by using the dual gas cooler. Finally, a predictive correlation for optimal intermediate temperature determination with ambient and water-feed temperature as independent variables is proposed, which provides a theoretical basis for the proposed system to realize efficient control in the industrialization process.

Exploiting the adsorption of simple gases O2 and H2 with minimal quadrupole moments for the dual gas characterization of nanoporous carbons using 2D-NLDFT models

For years, the characterization of carbon pore size distribution (PSD) has been dominated by the analysis of N2 isotherms. Recently, the IUPAC Technical Report (2015) recommended Ar as inert gas for this analysis. N2 molecule due to its significant quadrupole moment may selectively interact with the polar surface sites and affect the isotherm measurement. CO2, another gas that is often used for the characterization of microporous carbons exhibits even higher quadrupole moment than N2. In the present study, we substitute N2 and CO2 with O2 and H2 gases that have much lower quadrupole moments. The PSD calculations are performed using molecular models based on classical and quantum corrected two-dimensional nonlocal density functional theory (2D-NLDFT).We compare the results of the dual gas analysis methods by the simultaneous fit of our models to N2 & CO2, and O2 & H2 isotherms for several reference carbon samples and demonstrate consistency between the results derived from both pairs of isotherms.A fundamental and practical benefit of using the dual gas analysis method is the ability to obtain the full micro and mesopore PSD by using a partial O2 isotherm without low-pressure data in combination with full H2 isotherm both measured at 77 K.

Over Pressure Risk Mitigation with SCADA in a Natural Gas Distribution System

Natural gas distribution providers have periodic and reactive maintenance plans that are not providing enough feedback and data to establish proper predictive analysis for failure, especially on distribution gas regulator station that are regulating gas from transmission pressure to a safe customer distribution pressure, these stations are the only overpressure safeguard and the highest risk at the same time. With the recent advances in computer and telecommunications technologies, some major gas utilities initiated more robust predictive risk analysis plans by introducing SCADA supervisory control and data acquisition to gas distribution, mainly monitoring gas regulator stations and their behavior based on their established overpressure prevention philosophies and long-term predictive analysis goals. This study outlines a full SCADA monitoring solution on a dual run gas distribution regulator station equipped with primary overpressure protection and redundancy options. RTU (Remote Terminal Units) containing flow and pressure monitoring transmitters are installed at specific pressure reduction points in the station piping. Unlike common monitoring practice, we are introducing mid-stream pressure monitoring between the monitor and regular valves, filter differential and flow measurement in our proposed SCADA set up. This system provides real time visibility and data to the gas control room to quickly recognize abnormal or emergency events and assess the current health of regulator equipment. The outlined risk mitigations in this study are created based on identified risks of overpressure under several regulation failure modes of the regulators in standby and working modes. Our SCADA solution introduces means to enhance deductive analysis and predictability for gas control departments and monitoring groups leading to a safer and more reliable gas distribution system, improving emergency response and creating more comprehensive maintenance plans driven by long term predictive risk plans.

A Micromachined Metal Oxide Composite Dual Gas Sensor System for Principal Component Analysis-Based Multi-Monitoring of Noxious Gas Mixtures.

Microelectronic gas-sensor devices were developed for the detection of carbon monoxide (CO), nitrogen dioxides (NO2), ammonia (NH3) and formaldehyde (HCHO), and their gas-sensing characteristics in six different binary gas systems were examined using pattern-recognition methods. Four nanosized gas-sensing materials for these target gases, i.e., Pd-SnO2 for CO, In2O3 for NOX, Ru-WO3 for NH3, and SnO2-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were fabricated using a microsensor platform. Principal component analysis of the experimental data from the microelectromechanical systems gas-sensor arrays under exposure to single gases and their mixtures indicated that identification of each individual gas in the mixture was successful. Additionally, the gas-sensing behavior toward the mixed gas indicated that the traditional adsorption and desorption mechanism of the n-type metal oxide semiconductor (MOS) governs the sensing mechanism of the mixed gas systems.

The competitive behavior for O2 and CO2 reaction during char oxy-fuel combustion: effects of temperature and inherent minerals

Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential for the boiler design, but challenging for O2/CO2 combustion since char reaction behavior within dual reactive gas media is complex. There is also a doubt of whether or not the O2 reaction and CO2 reaction occur independently, whereby the overall rate would be simply additive, or the two reactions compete for the same char actives, in which case the rate prediction could be more complicated. Here, the competitive behavior for O2 and CO2 reactions of char active sites was investigated via thermogravimetric approach, with a focus on the effect of temperature and inherent mineral composition. For char combustion within O2/CO2 environment with molar fractions of 30/70, the contribution of O2 to char consumption is the same as the O2 reaction alone. However, as being out-competed by O2, only 37% CO2 could occupy char active sites and react. Consequently, the overall char reaction rate within O2/CO2 is only 83% of the sum of that for individual gases at 900 °C. With increasing temperature, this ratio becomes even smaller, as the contribution of CO2 that being out-competed (to the sum of individual gases) is larger. With increasing O2 fraction, it occupied more active sites, thus further inhibiting CO2 reaction. The inherent alkali and alkaline earth metal provides the char with more active sites, thus muting the competition and inhibition for CO2 gasification.

An Effective Optical Dual Gas Sensor for Simultaneous Detection of Oxygen and Ammonia.

The development of a simple, low-cost sensor for the effective sensing of multiple gases in industrial or residential zones has been in high demand in recent days. In this article, we have proposed an optical sensor for the dual sensing of oxygen (O2) and ammonia (NH3) gases, which consists of oxygen and ammonia-sensitive fluorescent dyes coated individually on both sides of a glass substrate. An ethyl cellulose (EC) matrix doped with platinum (II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) serves as the oxygen-sensing material, whereas the NH3-sensing material includes an eosin Y fluorescent indicator immobilized within a cellulose acetate (CA) matrix. Both the oxygen and ammonia-sensitive materials were excited by the same LED light source with a 405 nm peak wavelength, while the corresponding emissions were detected separately for the selective sensing of the gases under study. The dual gas sensor exhibits maximum sensitivities of around 60 and 20 for oxygen and ammonia gases, respectively. The high sensitivity and selectivity of the proposed optical dual sensor suggests the feasibility of the simultaneous sensing of oxygen and ammonia for practical applications.

Energetic and exergetic thermal analysis of an inline-airflow solar hybrid dryer

Uniform air distribution inside drying chamber is key factor to reduce energy consumption along with drying uniformity. A detailed thermal analysis (energy and exergy based) was performed for a newly developed inline-airflow solar hybrid dryer (coupled with solar evacuated tube collector and gas burner). The experiments were performed using green chilies at 60 °C under three modes of heating sources i.e. dual (gas + solar), gas and solar. Thermal analysis revealed that energy utilization varied in the ranges of 0–17 kJ/sec (dual), 0–16 kJ/sec (gas), 0–13 kJ/sec (solar), energy utilization ratios were in the ranges of 0–56.8% (dual), 0–60% (gas), 0–47.8% (solar) while values of exergy losses were 2.26–5.41 kJ/kg (dual), 2.45–5.56 kJ/kg (gas) 1.48–4.00 kJ/kg (solar), and exergy efficiencies were in the ranges of 33.95–74.11% (dual), 24–73.58% (gas),17–69% (solar). Heating component that comprised of heat exchanger–evacuated tube collector handled major part of energy possessing higher exergetic factor (54.37) and improvement potential rate (2.016). The values of specific evaporation and product energies were calculated 5.16, 5.77, 4.45 MJ/kg and 22.28, 24.90, 19.19 MJ/kg for dual, gas and solar modes of heating respectively. The study provides a detailed and sequential procedure to conduct thermal analysis of an industrial drying unit employing hybrid source of heating for design assessment and optimization.

Dual Selective Gas Sensing Characteristics of 2D α-MoO3-x via a Facile Transfer Process.

Metal oxide-based gas sensor technology is promising due to their practical applications in toxic and hazardous gas detection. Orthorhombic α-MoO3 is a planar metal oxide with a unique layered structure, which can be obtained in a two-dimensional (2D) form. In the 2D form, the larger surface area-to-volume ratio of the material facilitates significantly higher interaction with gas molecules while exhibiting exceptional transport properties. The presence of oxygen vacancies results in nonstoichiometric MoO3 (MoO3-x), which further enhances the charge carrier mobility. Here, we study dual gas sensing characteristics and mechanism of 2D α-MoO3-x. Herein, conductometric dual gas sensors based on chemical vapor deposited 2D α-MoO3-x are developed and demonstrated. A facile transfer process is established to integrate the material into any arbitrary substrate. The sensors show high selectivity toward NO2 and H2S gases with response and recovery rates of 295.0 and 276.0 kΩ/s toward NO2 and 28.5 and 48.0 kΩ/s toward H2S, respectively. These gas sensors also show excellent cyclic endurance with a variation in ΔR ∼ 112 ± 1.64 and 19.5 ± 1.13 MΩ for NO2 and H2S, respectively. As such, this work presents the viability of planar 2D α-MoO3-x as a dual selective gas sensor.

TOOL CONTROL THE CONCENTRATION OF CARBON DIOXIDE IN THE FLUE GAS BOILERS BASED ON THE OPTICAL ABSORPTION METHOD

The methodology for controlling the concentration of carbon dioxide in flue gases from boilers is an optical absorption method with improved metrological characteristics. Studies done in the article, provided the new, scientifically-based theoretical and practical results that are essential for improving the accuracy at the required speed process, control the carbon dioxide concentration in dual gas boilers based on the optical absorption method with compensation effect on the factors optical converter.