Effects Of Operation Mode Research Articles

The effect of operation modes on the thermal performance of a novel multi-tubular phase change material-filled earth-air heat exchanger

The phase change material (PCM)-filled earth-air heat exchanger (PAHE) represents a technology aimed at reducing energy consumption in outdoor air pretreatment. This study develops a two-dimensional numerical model of the proposed multi-tubular PCM-filled earth-air heat exchanger using the finite difference method, with a computational program implemented in MATLAB. The model's accuracy is validated against experimental data. The results indicate that the proposed system exhibits superior performance overall during the four-month operation in Chongqing, China, achieving a maximum temperature drop of 5.26 °C during the nine-day investigation period. Furthermore, the operating modes (Conditions 3, 4, and 5), when combined with night purging, enhance the cooling performance and temperature drop of the proposed system, while the liquid fraction of the PCM is distributed more uniformly throughout the daily cycle. The soil and PCM units in condition 5 exhibited the least thermal accumulation and the highest coefficients of performance during the nine-day examination period. The findings of this study enhance the understanding of the impact of operating modes on the thermal performance of PAHE systems.

Supercritical fluid impregnation of phenolic compounds from passion fruit bagasse in corn starch aerogels: Phase behavior and effect of operation mode

This work investigated the phase behavior of the system sc-CO2 + ethanolic extract of passion fruit bagasse (EEPFB) and the effect of operation modes on the supercritical fluid impregnation (SFI) of phenolic compounds from EEPFB in corn starch aerogels. The total reducing capacity, antioxidant capacity (FRAP and ORAC), piceatannol amount and SFI yield (%) were evaluated. Three of the four system compositions showed the formation of a solid phase. SFI in static mode provided the best TRC, FRAP, and ORAC results. There were no significant differences in the amount of piceatannol and yield (%). The nitrogen adsorption/desorption test possibly indicates the filling of the aerogel pores with EEPFB and images of the aerogel before and after SFI suggest the incorporation of phenolic compounds into the corn starch aerogels through precipitation.

Assessing phosphorus recovery from anaerobic digestion effluent of tapioca starch processing in a pilot – scale fluidized – bed homogeneous crystallizer: Effects of operation modes

This present study aimed to investigate the effects of two crystallization operation modes, batchwise operation (BO) and continuous operation (CO), on P recovery efficiency and characteristics of precipitates in a pilot – scale fluidized – bed homogenous crystallizer, using real anaerobic digestion (AD) effluent derived from tapioca starch processing as influent. Characterization techniques, including SEM – EDX, powder XRD, profile – matching, FT – IR, and crystal size distribution (CSD) analysis, were employed to identify phase compositions. Additionally, the purity and %P content of the target product were quantified using principles of hierarchical equilibrium thermodynamics and elemental analysis. As a result, the highest P recovery efficiency was 72.5 % for BO and 83.2 % for CO at a pH of 9 and a mixing rate of 400 rpm. Phase identification results revealed that struvite formed with Ca – rich solids, such as hydroxyapatite (HAP), notably exhibited higher impurity levels originating from CO modes. Precipitates from BO modes predominantly held 65 – 75 % struvite, with %P content ranging from 7.4 to 13.1 % — surpassing that of single superphosphate fertilizer (SSP, 18 – 22 % as P2O5), resulting in a suitable process in this study. Moreover, results obtained from the cost – benefit analysis (CBA) highlighted that BO scenario had economic viability (NP +0.05 to +1.53) with an estimate production cost of 3.47 USD/kg Premoved. Hence, the findings not only indicated that real AD effluent is suitable for P recovery, yielding high – quality struvite products, but also contribute to understanding the nuanced impact of crystallization modes on recovery yields and characteristics. This insight is invaluable for optimizing the process, leading to environmental benefits through reduced P and nitrogen discharge.

New insights into syntrophic ethanol oxidation: Effects of operational modes and solids retention times

Anaerobic ethanol oxidation relies on syntrophic interactions among functional microorganisms to become thermodynamically feasible. Different operational modes (sequencing batch reactors, SBRs, and continuous flow reactors, CFRs) and solids retention times (SRT, 25 days and 10 days) were employed in four ethanol-fed reactors, named as SBR25d, SBR10d, CFR25d, and CFR10d, respectively. System performance, syntrophic relationships, microbial communities, and metabolic pathways were examined. During the long-term operation, 2002.7 ± 56.0 mg COD/L acetate was accumulated in CFR10d due to the washout of acetotrophic methanogens. Microorganisms with high half-saturation constants were enriched in reactors of 25-day SRT. Moreover, ethanol oxidizing bacteria and acetotrophic methanogens with high half-saturation constants could be acclimated in SBRs. In SBRs, Syner-01 and Methanothrix dominated, and the low SRT of 10 days increased the relative abundance of Geobacter to 38.0%. In CFRs, the low SRT of 10 days resulted in an increase of Desulfovibrio among syntrophic bacteria, and CFR10d could be employed in enriching hydrogenotrophic methanogens like Methanobrevibacter.

Simulation of turning maneuver using the 4+2DOF method in planing and semi-planing modes

Planing craft maneuver is dominated by attitude change which requires a 6DOF motion equations. Recently, 4+2DOF method as a kind of the 6DOF motion equations was introduced in which heave and pitch motion are replaced by rise-up and dynamic trim. The 4+2DOF method was employed for the turning maneuver that start and end in the planing mode. In this study, the application of 4+2DOF method is extended to examine a turning maneuver that starts in the planing mode and ends in the semi-planing mode. Simulations are conducted on a model which has already been tested in full-scale maneuver trials. Maneuver Hydrodynamic Coefficients (MHCs) are concluded from Plannar Motion Mechanism (PMM) tests in both the planing and semi-planing modes in a range of forward speeds. Having a verified computer code, effects of operation modes and forward speed are studied on the turning maneuver. This study quantitatively depicts that the Steady Turning Diameter (STD) in the planing mode is about four times larger than the semi-planing mode. It is also concluded that STD of a turning maneuver starts and ends in the planing mode, is about 2.5 times larger than that starts in the planing mode and ends in the semi-planing mode.

Effect of operation mode on membrane fouling from traditional Chinese medicine water extracts

Membrane technology is a viable alternative to many conventional methods currently used to process traditional Chinese medicine (TCM). However, membrane fouling is a significant obstacle to the application of membrane technology in TCM. In this study, the ultrafiltration (UF) membrane fouling from TCM water extracts under constant transmembrane pressure (TMP) and constant flux operation was studied in connection with critical and threshold flux determinations. Meanwhile, the physicochemical foulant–membrane interactions were analyzed using the extended Derjaguin, Landau, Verwey, and Overbeek (XDLVO) theory. At constant TMP operation, the high pressure resulted in a rapid drop in permeate flux at the start of the filtration period, but the steady-state fluxes did not increase significantly with an increase in TMP. At constant flux operation, the TMP increased somewhat when the permeate flux was below the threshold flux. Fouling was severe above the threshold flux, and the TMP rapidly increased. By displaying fouling resistance as a function of permeate volume, the constant flux operation was compared to a constant TMP operation beginning at the same flux imposed during the constant flux operation. Below the threshold flux, fouling resistance was similar for constant TMP and constant flux operations. However, above the threshold flux, fouling resistance under constant flux operation was much greater than fouling resistance under constant TMP operation. The results of physicochemical interactions showed that there are attractive interactions between hydrophobic membrane and foulants in the TCM water extracts. These interactions should be considered a key factor leading to serious membrane fouling.

Photodegradation of free estrogens driven by UV light: Effects of operation mode and water matrix

Estrogens are endocrine disrupting chemicals that have been frequently detected in diverse water matrices (e.g. surface water, wastewater and drinking water) and caused a series of health risks. This study was aimed at investigating the photochemical degradation of free estrogens estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethyl estradiol (EE2) upon the monochromatic irradiation (253.7 nm). Concerning the practical installation of photolysis treatment, exposing the impacts of photoreactor operation mode (stationary or up-flow) and the water matrix (ultrapure water or natural surface water) on the photolytic behaviour of estrogens was of high importance. The pseudo-first-order rate constants showed that E1 was the most susceptible to UV radiation among chosen estrogens due to its high molar absorption coefficient of 402.4 M−1 cm−1 and quantum yield of 0.065 mol E−1 at λ = 253.7 nm. Moreover, the up-flow mode and the surface water matrix collected from a lake in Regent's Park (London) were found to favour the photodegradation of estrogens due to the introduction of more dissolved oxygens and promotion of reactive oxygen species (ROS) formation. These findings may shed light on the photochemical behaviour of estrogens in some specific scenarios.

Testing and comparison of a thermodynamic vent system operating in different modes in a liquid nitrogen tank

• A multifunctional system was established for cryogen storage technology evaluation. • Four different pressure control modes were compared on the same testing system. • A new parameter was proposed for evaluating contribution factors to pressurization. • Ullage heating is more effective to self-pressurization than liquid evaporation. • Active TVS vents more fluid for depressurization than passive TVS does. Thermodynamic vent system (TVS) has been considered as a promising method for pressure control in cryogenic propellant tanks in microgravity environment. TVS could be operated in different modes, namely, the mixing-venting (MV) mode, the mixing-only (MO) mode, the mixing-only followed by mixing-venting (MOMV) mode, and the passive venting (PV) mode. An experimental investigation on the effect of operation mode on the TVS performance was conducted by using liquid nitrogen as the liquid oxygen simulant on a testing facility named Multi-functional Cryogenic Test System. Results of those four operating modes tests were compared regarding the ullage cooling effect, liquid temperature, pressure control capability, and mass loss. It was found that with the help of spraying, the MV mode and the MO mode cooled the ullage more effectively than the PV mode did. However, the PV mode is more effective in suppressing the increase of the liquid temperature. A non-dimensional parameter η has been proposed for comparison between the ullage heating and the liquid evaporation contribution to the pressurization in cryogenic fluid storage tanks. For the mixing-venting mode, the ullage heating is the main force that pressurizes the tank when the liquid is subcooled, while when the liquid is saturated, the evaporation takes over the role. Moreover, the MOMV mode performs the best in reducing mass loss within 0–1500 min. The results will be useful to make a control strategy for the operation of pressure control in on-orbit cryogenic tanks through thermodynamic venting method.

Effect of operation modes on the thermal performance of EAHE systems with and without PCM in summer weather conditions

This work reports a transient numerical study of the thermal performance of two earth-to-air heat exchanger systems (EAHE) in summer weather conditions in a desertic climate. One conventional EAHE and the other with a phase change material (PCM) in the entrance under four different modes of operation/recovery (continuous, intermittent, intermittent-PCM-natural convection, and intermittent-PCM-mixed convection) to find the system that guarantees the best thermal performance. A detailed validation was made by comparing it with experimental and numerical data reported in the literature, under similar climatic conditions. The EAHE-PCM systems were used to reduce the thermal saturation of the soil, bringing with it an increase in the thermal performance of the EAHE system. The behavior of temperatures of the cooled air, soil, and PCM for each system are presented and analyzed. Besides the coefficients of performance are compared for each EAHE. It was found that the PCM selection is completely dependent on the environmental conditions in which the EAHE-PCM system will be used, with the right PCM the air temperature that is in contact with the soil was decreased up to 2.65 °C. The thermal recovery through the night injection of air (colder than soil average temperature) is an effective way to achieve a colder outlet temperate during the useful hours of cooling, besides, night injection was able to decrease the saturation factor from 0.356 to 0.296. The case that shows the best-modified coefficients of performance (COP*) is the ones with PCM and only passive cooling during the recovery mode (328.16) because in this case, the air blower has less operation time, in the other hand, the worst COP is seen in the case without PCM and all-day force convection (158.16), the case with PCM and night injection shows a COP* of 268.43.

Effect of operational modes on the train-induced airflow and thermal environment in a subway station with full-height platform bailout doors

Train-induced unsteady airflow (TIUA) has a considerable effect on the ventilation and thermal environment of a subway system. Because of the complexity of a subway ventilation network and the variability of train activity, analytical and numerical methods are limited in reflecting the actual situation. In this study, a field test on the TIUA and air temperature in a subway station with full-height platform bailout doors (PBDs) was conducted under four operational conditions. The results showed that the train running parameters and operational modes, including the piston vent shafts, bypass ducts and cotton curtains at the entrances, had substantial effects on the TIUA and thermal environment. The air inflow and outflow rates through the entrances increased by 20.99% and 39.66%, respectively, as the train interval decreased by 104 s (case 2). Moreover, there was a greater difference in the air inflow rate through the entrances under different operational modes. Furthermore, uninstalling the cotton curtains increased the air inflow and outflow rates by 2.09- and 1.36-fold, respectively, at a train interval of 510 s (when comparing case 1 and case 2). In addition, removing the cotton curtains, the maximum decreases in air temperature in the entrances, hall, and platform were approximately 5.10 °C, 4.85 °C, and 1.39 °C, respectively, and the thermal environment with the single open system and closed bypass ducts condition might be better than that with the internal circulation system and open bypass ducts condition. This study provides first-hand data for ascertaining the characteristics of the TIUA and optimizing subway operational modes.

PEM Electrolysis‐Assisted Catalysis Combined with Photocatalytic Oxidation towards Complete Abatement of Nitrogen‐Containing Contaminants in Water

Electrolysis‐assisted nitrate (NO3 −) reduction is a promising approach for its conversion to harmless N2 from waste, ground, and drinking water due to the possible process simplicity by in‐situ generation of H2/H/H+ by water electrolysis and to the flexibility given by tunable redox potential of electrodes. This work explores the use of a polymer electrolyte membrane (PEM) electrochemical cell for electrolysis‐assisted nitrate reduction using SnO2‐supported metals as the active cathode catalysts. Effects of operation modes and catalyst materials on nitrate conversion and product selectivity were studied. The major challenge of product selectivity, namely complete suppression of nitrite (NO2 −) and ammonium (NH4 +) ion formation, was tackled by combining with simultaneous photocatalytic oxidation to drive the overall reaction towards N2 formation.

Effect of Operation Modes on Hydrodynamic Performance of Pilot-Scale Pulsed Disc-and-Doughnut and Pulsed Sieve-Plate Columns: A Comparative Study

ABSTRACT This work presented hydrodynamic performance of pilot-scale pulsed sieve-plate column (PSPC) and pulsed disc-and-doughnut column (PDDC) in different operation modes for the uranyl nitrate/30% (v/v) tributyl phosphate in kerosene system. It was found that the hydrodynamic performance of PSPC and PDDC was similar in the aqueous continuous mode, in which the stainless-steel internal plates were not wettable to the dispersed phase. In the organic-continuous mode, more energy inputting was required to attain a similar dispersion efficiency than that in the aqueous continuous mode. Moreover, the liquid–liquid flow in PSPC exhibited poorer dispersion efficiency than that in PDDC and was easier to run into the flooding regime as the throughput was increased. Wettability of the stainless-steel internal plates and geometrical structure differences between the sieve plates and disc/doughnut plates were the main reasons for these phenomena. Correlations for the prediction of holdup in both PDDC and PSPC were proposed based on experimental results.

The Effect of Operating Modes on the Response of Ammonia Sensors Based on Tin Dioxide Films

The influence of operating modes on the response of ammonia sensors based on tin dioxide films has been studied. Samples have been obtained as a result of high-frequency magnetron sputtering of a SnO2:Sb target on sapphire substrates with predeposited Pt electrodes and a heater. Varying the heating cycle duration and reducing the cooling cycle temperature may increase the response by one or two orders of magnitude. The results are explained as being due to the change in the density of chemically adsorbed oxygen on the surface of the SnO2:Sb film depending on the temperature regime.

Bioelectrochemically-assisted nitrogen removal in osmotic membrane bioreactor.

Nitrogen removal in osmosis membrane bioreactor (OMBR) is important to its applications but remains a challenge. In this study, a bioelectrochemically-assisted (BEA) operation was integrated into the feed side of OMBRs to enhance nitrogen removal, and sodium acetate was served as a draw solute and supplementary carbon source for the growth of denitrifying bacteria due to reversed-solute. The effects of operation mode and influent ammonium (NH4 +) concentration were systematically examined. Compared to a conventional OMBR, the integrated BEA-OMBR achieved higher total nitrogen removal efficiency of 98.13%, and chemical oxygen demand removal efficiency of 95.83% with the influent NH4 +-N concentration of 39 mg L-1. The sequencing analyses revealed that ammonia-oxidizing bacteria (0-0.04%), nitrite-oxidizing bacteria (0-0.16%), and denitrifying bacteria (1.98-8.65%) were in abundance of the microbial community in the feed/anode side of integrated BEA-OMBR, and thus BEA operation increased the diversity of the microbial community in OMBR. Future research will focus on improving nitrogen removal from a high ammonium strength wastewater by looping anolyte effluent to the cathode. These findings have demonstrated that BEA operation can be an effective approach to improve nitrogen removal in OMBRs toward sustainable wastewater treatment.

Effect of Operating Mode of the Input-Output Ports of Complex Functional Devices on Indicators of the Pulsed Electric Strength of the Product

We test the durability of the simplest AVR ATtiny13A microcontroller (from Atmel) to the effects of single voltage pulses depending on the input-output port configuration. The dependence of the impulse electric strength of the microcontroller on the operation mode of the ports is discovered.

Experimental Investigation on Drawdown of Floating Particles in Viscous Systems Driven by Coaxial Mixers

In view of the current situation of single form and low efficiency, a coaxial mixer with wide adaptability was combined with the drawdown of floating particles in viscous systems, and the effects of operation mode, impeller type, impeller diameter, impeller submergence, system viscosity, solid concentration and particle size were investigated experimentally. It is found that the coaxial mixer under corotation mode can achieve the critical drawdown of floating particles with lower speed and power than the corresponding single-shaft mixer, and the advantage becomes more obvious with increasing system viscosity and solid volume fraction. Under the same conditions, compared with the axial and radial flow impellers, the mixed flow impeller with down-pumping mode can effectively draw the floating particles down with the lowest critical speed and power. Moreover, a larger impeller diameter and smaller impeller submergence are recommended for the drawdown of floating particles, but the impeller diameter should not exceed half of the vessel diameter.

Analysis of an Active Superconducting Current Controller (ASCC) Considering the Transient Stability and OCR Operation in Transmission and Distribution Systems

The Active Superconducting Current Controller (ASCC) is a new type of Superconducting Fault Current Limiters (SFCL) which can limit the fault current in different modes. It also has the particular abilities of compensating active and reactive powers for electrical networks. In this paper, it is confirmed that the performance of ASCC in different operating modes introduces a limiting impedance in series with the network which can even degrade the transient stability and the operation of the Over-Current Relays (OCR) employed in a power system. In addition, the model of a three-phase ASCC is simulated, and the effect of descriptive modes on the current limiting level is investigated. For the transient stability analysis, a single machine-infinite bus system is tested, and the effect of operation modes is studied based on an equal area criterion obtaining the critical time and the critical angle. Modifying the setting parameters of OCR such as time dial and pick-up current, the protective coordination is also studied in different operating modes.

Effect of operational modes on nitrogen removal and nitrous oxide emission in the process of simultaneous nitrification and denitrification

The effects of operational modes (fully aerobic mode and anoxic–aerobic mode) on simultaneous nitrification and denitrification (SND) process were investigated to reveal the different characteristics of nitrogen removal and nitrous oxide (N2O) emission. Results indicated that total nitrogen (TN) removal and SND efficiencies under anoxic–aerobic mode increased by 17.8% and 10.1% in comparison with fully aerobic mode. Furthermore, N2O emission in the anoxic–aerobic SND was much lower than in fully aerobic SND. The amount of N2O emitted per cycle in the fully aerobic SND was 21.9±7.1% of the removed TN, which was three times higher than 7.0±1.6% observed in the anoxic–aerobic SND. Denitrification by nitrifiers was the main source of N2O emission in both systems. High-throughput pyrosequencing analysis revealed a greater abundance of Nitrosomonas sp. and Mesorhizobium sp. in fully aerobic SND than anoxic–aerobic SND, which were closely associated with N2O emissions.

Effects of operation mode on self-alkalization of high-load denitrifying reactor

To study the alkalization issue and its potential effects on high-load denitrifying system, the effects of operation mode on self-alkalization of high-load denitrifying reactor were investigated. The results showed that both the increase of substrate concentration and decrease of hydraulic retention time (HRT) can induce notable self-alkalization of high-load denitrification reactor (with the nitrogen loading rate (NLR) higher than 25kg Nm−3d−1). The effluent pH surpassed the 9.20 when the influent pH value was 7.0±0.1. The self-alkalization of denitrification process originated from the nitrate reduction, while the methanol oxidation could alleviate the self-alkalization by neutralizing OH− and setting up a buffering system of HCO3−/CO32−. At the same NLR, the self-alkalization induced by increase of substrate concentration was remarkably stronger than that induced by decrease of HRT. Keeping the nitrate concentration below inhibition concentration improved the performance of high-load reactor and alleviated the self-alkalization.

Performance of Direct Carbon Fuel Cells Operated on Coal and Effect of Operation Mode

Previous experimental results have shown that a system with molten carbonate and solid oxide electrolyte is feasible for Direct Carbon Fuel Cell (DCFC). A study is presented to investigate cell performance with a range of solid carbon (i.e. coals, biochars, graphite) and operation mode in this hybrid electrolyte system. The results show that less crystalline coal with high fixed carbon, low sulfur, medium volatile material and moisture is best suited to this system. Using high rank of fuel such as anthracite coal, good cell performance can be obtained only by elevating temperature and with adequate pretreatment to remove impurities. Discussion of cell operation indicates that cell degradation and operation failure were due to coal agglomeration, ash buildup, and limited fuel supply in potentiostatic mode. Instead, galvanostatic operation gave stable cell performance over 60 hours. This result allows better understanding of anode reaction mechanism on the hybrid electrolyte system. Thus, long-term operation is promised when suitable solid fuel and optimized operation parameters are applied.