Medium Flow Rate Research Articles

TAGUCHI-BASED OPTIMIZATION OF HEAD AND NECK CT ANGIOGRAPHY: IN-VIVO ENHANCED TRIGGERED TIMING FOR 600 PATIENTS

The Taguchi-based optimization of head and neck CT angiography (CTA) using in-vivo enhanced triggered timing for 600 patients was accomplished in this study. A total of 600 patients were categorized into three (test, verification, and implementation groups with 360, 120, and 120 patients, respectively). The patients in the test group were randomly assigned into 18 sub-groups according to Taguchi L[Formula: see text](2[Formula: see text]) orthogonal array for optimizing factor combinations of head and neck CTA. The signal-to-noise ratio was defined as a high LRA/US ratio (both left and right arterial pressure divided by upper sinuses’ one) and low stdev. The seven factors of CTA were: (A) left- or right-hand injection; (B) tube current, mA; (C) kilovoltage peak, kVp; (D) contrast media concentration; (E) FOV; (F) flow rate of contrast media; and (G) rotation time for one CTA loop. With the Taguchi unique organization, 18 sub-groups (each containing 20 patients’ real LRA/US ratios) could cover 1458 cases and provide the appropriate reliability. The optimal factor combination was identified as follows: (A) left-hand injection, (B) tube current of 280[Formula: see text]mA, (C) 100[Formula: see text]kVp, (D) contrast media concentration of 60%, (E) FOV of 250[Formula: see text]mm, (F) contrast media flow rate of 4.0[Formula: see text]ml/s, and (G) rotation time for one CTA loop of 0.9[Formula: see text]s. The optimal suggestion was validated in the verification group with 120 patients and applied to the implementation group with 120 patients. The successful factor combination is instrumental in defining a standard protocol for medical staff in deriving the maximal LRA/US value ([Formula: see text]) of head and neck CTA.

Injection rate of contrast medium affects diagnostic ability of dynamic contrast-enhanced magnetic resonance imaging for endometrial carcinoma: a prospective cohort study

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) can obtain semi-quantitative or quantitative parameters of tumors by capturing the images before and after injection of contrast medium. However, there has been no further research on the effect of flow rate of contrast medium on image quality and parameter sensitivity of DCE-MRI in endometrial carcinoma (EC). This was a prospective cohort study enrolling patients who were suspected of EC between January 2018 and June 2020. The baseline data of participants were collected. Post-surgical histological examination acted as the gold standard of EC diagnosis and some characteristics of tumors were recorded. We calculated 3 important parameters of DCE-MRI, including volume transfer constant (Ktrans), flux rate constant (Kep), and extravascular extracellular volume fraction (Ve), according to the MRI system. The image quality in DCE-MRI imaging was evaluated according to contrast, resolution, artifact, signal-to-noise ratio, and scanning time. To evaluate the diagnostic ability of DCE-MRI with different injection rate, receiver operating characteristic (ROC) curve was generated and the area under curve (AUC) was calculated. According to the different injection rate of contrast medium, participants were divided into three groups, including 2, 3, and 4 mL/s group. It was found that there were more grade 1 EC in the 3 mL/s group (52.4%) than other two groups (34.3% and 23.3%, respectively), and the difference was significant (P=0.021). No other significant differences were found among all other variables. It was found that Ktrans was much higher in the 4 mL/s group than in other two groups (P<0.001). Also, Ve was much higher in the 4 mL/s group than in other two groups (P<0.001). However, no significant difference was found in Kep between three groups (P=0.633). Besides, the 4 mL/s group had the highest quality of all three groups (P<0.001). The sensitivity, specificity, and accuracy were highest in 4 mL/s group. The AUC in three groups were 0.822, 0.832, and 0.888 in the 2, 3, and 4 mL/s group, respectively. The DCE-MRI measurement is useful for the diagnosis of EC, and faster injection rate may be beneficial to improve diagnostic accuracy and image quality.

Proton Exchange Membrane Fuel Cell Ejector Test Platform Design and Ejector Test Analysis

The hydrogen recirculation system is essential to the performance of the fuel cell system; the ejector device plays an important role in the hydrogen recirculation system. In this paper, a test platform which can simulate the fuel cell anode system is integrated for ejector performance testing. Based on the ejector test platform, an ejector device was tested under different operating conditions. The design of the ejector test platform, the test method and test process are introduced in detail. The test results of the ejector are compared with the Computational Fluid Dynamics (CFD) simulation results of different turbulence models. The results show that the standard k-e model is more accurate than other turbulence models at small and medium flow rates. At a large flow rate, the realizable k-e model has a higher simulation accuracy than other turbulence models.

Использование теории подобия при проектировании турбин газотурбинных двигателей

At present, in the promising development of gas turbine engines compared to at least the fourth generation products, there have been significant changes in the approaches to the design of engine. First of all, it is an increase in maximum values of temperature, gas pressure and circumferential flow speeds, an increase in power of the turbine stage, as well as improvement of the turbine manufacturing technology. All these factors lead to the fact that when designing the flow parts of the gas turbine, it is necessary at the fixed design flow rate of the working medium in the engine, i.e. at the fixed diameters, lengths of the nozzle and rotor blades forming the outline of the inter-blade channels, to increase the blade chords with the corresponding reduction of the number of blades in the row. The increase in turbine stage power associated with the increase in temperature, pressure (density), and circumferential velocity increases the bending stresses leading to the need to increase chords at a fixed blade length. Significant reduction of number of blades in stages, simplifies technology of blades manufacturing. A substantial increase in the maximum gas temperature, in the perspective of more than 2000 K, also leads to the need to increase the blade chords, due to the need to place cooling cavities in the blades. As a result, contradictions arise with the use of similarity theory in the design of stages of turbines of different purpose, as some of the main requirements of similarity are violated — geometric similarity of blade channels of the flow part and then the use of the generally accepted number Re by the chord of blades loses meaning. Therefore, it is necessary to carry out detailed investigations of all flow parameters in four stages of turbines with detection of influence of change of rotor blade chords at equal length of blades. And justify the effect of change of rotor blade chords on physical processes in flow parts of turbines in engines of various purpose.

Comparison of Circular and Parallel-Plated Membrane Lungs for Extracorporeal Carbon Dioxide Elimination.

Extracorporeal carbon dioxide removal (ECCO2R) is an important technique to treat critical lung diseases such as exacerbated chronic obstructive pulmonary disease (COPD) and mild or moderate acute respiratory distress syndrome (ARDS). This study applies our previously presented ECCO2R mock circuit to compare the CO2 removal capacity of circular versus parallel-plated membrane lungs at different sweep gas flow rates (0.5, 2, 4, 6 L/min) and blood flow rates (0.3 L/min, 0.9 L/min). For both designs, two low-flow polypropylene membrane lungs (Medos Hilte 1000, Quadrox-i Neonatal) and two mid-flow polymethylpentene membrane lungs (Novalung Minilung, Quadrox-iD Pediatric) were compared. While the parallel-plated Quadrox-iD Pediatric achieved the overall highest CO2 removal rates under medium and high sweep gas flow rates, the two circular membrane lungs performed relatively better at the lowest gas flow rate of 0.5 L/min. The low-flow Hilite 1000, although overall better than the Quadrox i-Neonatal, had the most significant advantage at a gas flow of 0.5 L/min. Moreover, the circular Minilung, despite being significantly less efficient than the Quadrox-iD Pediatric at medium and high sweep gas flow rates, did not show a significantly worse CO2 removal rate at a gas flow of 0.5 L/min but rather a slight advantage. We suggest that circular membrane lungs have an advantage at low sweep gas flow rates due to reduced shunting as a result of their fiber orientation. Efficiency for such low gas flow scenarios might be relevant for possible future portable ECCO2R devices.

201 Impact of Water Flow Rate on Finishing Pig Performance

Abstract A survey of South Dakota pork producers in 2019 demonstrated that water flow rate for nipple drinkers was highly variable among barns. Sixty-eight percent had water flow rates above the recommended rate of 500–1,000 mL/min (NSNG, 2010). The objective of this study was to determine the impact of water flow rate on finishing pig performance during the summer months. A total of 396 mixed-sex pigs, in two groups, were utilized in a 77-day trial (34.55 to103.8 kg BW) with 6 pigs/pen. Pens were assigned to one of three water flow rates (high, medium, low) based on the 3-hole diameters of the commercial water nipples used in the facility (2.0, 1.0, 0.80 mm; n = 22 pens/treatment). Daily water usage was recorded for each treatment along with room temperature, outside temperature, and relative humidity. Individual pen water flow rate was recorded every two weeks. At every diet phase change (26± 2.6 days), feed disappearance and individual pig body weight were recorded. Water flow rates averaged 1846±188, 906±214, 508±100 mL/min for high, medium, and low flow rates, respectively. Daily water disappearance for high, medium, and low treatments were 6.8, 2.3, 1.7±3.2 liters/pig, respectively. Final body weight (BW; 103.8±7.4 kg) did not differ. Daily gain (ADG) from 34.5±4.5 to 55.5±4.6 kg BW was greatest (P &amp;lt; 0.05) for high treatment. Daily intake (ADFI) and gain:feed (G:F) from 55.5±4.6 to 79.1±5.3 kg BW were greatest (P &amp;lt; 0.05) for high treatment. Cumulative ADFI was 2.27, 2.18, 2.16±0.16 kg (P &amp;lt; 0.05) in high, medium, and low flow ranges, respectively. There was no differences in cumulative ADG or G:F. Water flow rate had a significant impact on ADFI although there was minimal impact on gain and G:F. Water nipples should be regularly checked as part of normal barn maintenance to ensure adequate, but not excessive, water is available.

Simulation research of TEG-ORC combined cycle for cascade recovery of vessel waste heat

ABSTRACT The waste heat of ships has the characteristics of large temperature gradient, huge recoverable amount and various properties. Traditional technologies such as thermoelectric power generation (TEG) and organic Rankine cycle (ORC) are difficult to take into account the different characteristics of the various types of waste heat from ships. In order to realize the efficient cascade utilization of various waste heat from ships, improve the efficiency and meet the stringent requirements of the new international carbon emission regulations, a cascade recovery system of ship waste heat based on TEG-ORC (thermoelectric power generation/organic Rankine cycle) is proposed in this paper. After designing of the TEG-ORC combined cycle experimental system, the simulation research has also been carried out. The effects of TEG bottom cycle scale, ORC working medium flow rate and evaporation pressure on system net output power, system power generation cost and bottom cycle ratio (QTEG/QORC ) are studied. The results show that the TEG-ORC combined cycle overcomes the limitation of single waste heat utilization method, realizes multi-stage utilization of ship waste heat, as well as improves the utilization of waste heat. Of course, the stability and safety of ORC bottom cycle operation are also promoted. The simulation results show that when the TEG bottom cycle scale is 22 pieces, ORC working medium flow rate is 0.44 kg/s, and ORC working medium evaporation pressure is 2.2MPa, the system economy is optimal. At this time, the system power generation cost is 0.26 $/kW·h, the system net output power is 2520.3 W, and the thermal efficiency is 23.33%.

Regional leachate discharge, monitoring and the associated riverine pollutants propagation model simulation of Sungai Sarawak in Malaysia

The Sarawak River also known as Sungai Sarawak serves as a vital water source for the residents in Kuching City and surrounding popular areas. Like many urban rivers elsewhere, Sungai Sarawak and its main tributaries are exposed to the potential pollution caused by leachate discharge and other pollutants. In order to preserve the cleaner water production, mundane sustainable water source as well as provide green environmental spots for tourist attraction, the water quality of the river needs to be continuously monitored to avoid or minimize potential unwanted water source contamination. The present work aims primarily to conduct a parametric study to predict the impact of leachate and other pollutants towards the water quality of Sungai Sarawak and its main tributaries. Relevant water quality parameters were selected as the indicators to assess the impacts of leachate discharges and other relevant pollutants by employing QUAL2K modelling system. The environmental parameters include DO, BOD, NH3-N, and total suspended solids (TSS) were evaluated. The simulation results illustrated the leachate discharge and other pollutants would not significantly deteriorate the water quality of Sungai Sarawak during normal operations (baseline situation). In the event of unwanted leakages, untreated and sudden release of leachate at Sungai Sarawak Kiri in normal riverine flow (Scenario #1) and low riverine flow (Scenario #2) would result in serious contamination of these rivers. High deterioration of Sungai Sarawak water quality also can be seen in Scenario #3 where the unwanted leakages or untreated and sudden release of leachate at the river mainstem with a low riverine flow which the concentrations of water quality parameters would degrade to Class III-V. The model also shows that three parameters that highly contributed to the deterioration of the baseline water quality based on Scenario #1, #2 and #3 which are BOD, NH3-N, and TSS. The BOD concentration increases by 270% in Scenario #1, 370% in Scenario #2 and 510% in Scenario #3. The NH3-N concentration increases by 390% in Scenario #1, 456% in Scenario #2 and 583% in Scenario #3. The TSS concentration also increases by 275% in Scenario #1, 367% increase in Scenario #2 and 385% in Scenario #3. This study recommends continuous monitoring, proper planning and, control of human activities to ensure that developments within the watershed do not contribute to the degradation of Sungai Sarawak water quality. The study also makes comparisons with other rivers elsewhere and comes up with recommendations in the effort to have more practical and implementable measures as a safety framework for Sungai Sarawak and its tributaries. Lastly, suitable advanced treatment systems such as industrial-scale hybrid membrane-microbial fuel cell systems are recommended for slow-to medium flow rate leachate-riverine treatment applications.

DETERMINATION OF CHARACTERISTICS OF THROTTLING DEVICE FOR PNEUMATIC SPRING

Purpose. This paper focuses on determination of the dependence of the working medium flow on the capacity of the throttling device, its geometric features and the pressure difference in the pneumatic spring cylinder and in the auxiliary reservoir. Methodology. Calculation of the dependence of the working medium and pressure drop is performed in two ways: 1) by numerical simulation of a stationary gas flow through a throttling element; 2) its analytical calculation expression using empirical relationships (control calculation to evaluate the reliability of numerical simulation results). For the calculation, three models of throttling devices were chosen. Dependence of the flow rate of the working medium on the capacity of the throttling device and its geometric features was determined based on the approximation of the dependency graphs of the pressure drop against the mass flow rate of the working medium. Findings. We obtained graphical dependencies between the pressure drop and the mass flow rate of the working medium from the two calculation options. Based on the results of calculations performed with the help of a software package with visualization of the results, we calculated a proportionality coefficient that describes the dependence of the working medium flow on the throttling device capacity and its geometric features for each of the throttling elements considered, with three degrees of closure. The air flow values, obtained by numerical simulation, are greater than the flow rates obtained from semi-empirical formulas. At the same time, they are in good qualitative agreement, and the quantitative difference averages 25%, which can be regarded as confirmation of the reliability of the nu-merical model. Based on the calculation results, we plotted the proportionality coefficient graphs against the degree of closure of the throttling device. Originality. The work allows determining the degree of influence of the frictio-nal component on the variation of the pressure difference in the pneumatic cylinder and the auxiliary reservoir of the pneumatic suspension system. Also, the work proposes a method to determine the dependence of the working medium on the capacity of the throttling device and its geometric features. Practical value. The ability to predict the operating parameters of the pneumatic system depending on the pneumatic resistance of the throttling device will improve the car running characteristics, increase the comfort of passenger transport, and also reduce the wear of the rolling stock and track gauge due to vehicle-track interaction.

Surface attached cultivation and filtration of microalgal biofilm in a ceramic substrate photobioreactaor

In this research, a capillary ceramic membrane was used as the substrate for surface attached cultivation of microalgae. A photobioreactor was constructed and tested for cultivation of Chlorella vulgaris adhered to this substrate. Optimum biomass productivity of 4.65 ± 0.42 g/m2/d was obtained during 8 days of cultivation by using the light intensity of 17,000 lx and BG-11 medium flow rate of 14 mL/d. The moisture content of the produced biofilm was around 80% which is comparable with the moisture content obtained from centrifugation of suspended algal cultures. It was shown that further dewatering is possible by applying vacuum to the ceramic membrane. According to these results, moisture content was reduced to 59% under the vacuum of 0.6 bar. It was also illustrated that after scrapping the biofilm, the remaining cells on the ceramic membrane can be used as an inoculum for the re-culture of the algal biofilm. According to the current results, the biomass productivity of the re-cultured biofilm was very close to the initially cultured biofilm, which indicates the applicability of the proposed system for long term cultivation of algal biofilm. Comparing the results obtained in this study with similar surface attached cultivation systems demonstrated the promissing performance of the designed photobioreactor with a lower culture medium consumption rate.

Hydrodynamic Causes of Vibration in the Pipe Bend of Process Pipelines

Hydrodynamic vibrations can occur both in pump piping at local resistances and in the pump, for example, when it’s operated outside the working area. Vibrations occurring in the hydraulic section of the pumps and associated pipings are transmitted to the mechanical section and can lead to breakdowns. Oscillations of pump piping can be caused by both hydrodynamic reasons and vortex formation at local resistances, and resonance with the natural frequencies of the piping. In some cases, the vibration of pipelines exceeds the permissible norms by 1.5-2 times. The range of vibration frequencies of a hydrodynamic nature directly depends on the flow rate of the working medium. As the latter decreases, the range also decreases. In any elbow of the pipeline, with a sufficient flow rate of the liquid, vortex formation occurs, which is the cause of forced vibrations. The values of the Strouhal number characterizing hydrodynamic phenomena in unsteady flow regimes for the flow of liquids in local resistances of pipelines have been studied very little.

Efficient photochemical vapor generation of bismuth using a coiled Teflon reactor: Effect of metal sensitizers and analytical performance with flame-in-gas-shield atomizer and atomic fluorescence spectrometry

Photochemical vapor generation (PVG) of bismuth was accomplished in a simple flow–injection system with a standard Hg low-pressure tube lamp and a coiled Teflon reactor. The influence of a reaction medium flow rate (irradiation time) and composition was investigated using a miniature diffusion flame atomizer and high-resolution continuum source atomic absorption spectrometry. Combination of 40% (v/v) acetic acid, 1.25% (v/v) formic acid and a metal sensitizer at a flow rate of 3 mL min−1 (irradiation time of 90 s) was found optimal. The use of various metals as sensitizers was studied to initiate and enhance PVG substantially. The evident positive effect was found for four metal cations and the enhancement effect was in the following order: Cu2+<Cd2+<Fe2+ ≪ Co2+. At 50 mg L−1 Co2+ as the sensitizer, the overall PVG efficiency of 54 ± 2% was determined from relative comparison of sensitivities obtained with PVG and liquid nebulization coupled simultaneously to inductively coupled plasma mass spectrometry. In order to reach low limits of detection (LOD) at low operation cost, a coupling of PVG to atomic fluorescence spectrometry was tested and conditions of atomization in two flame atomizers were optimized. A blank-limited LOD of 12 ng L−1 was obtained with an advanced flame-in-gas-shield atomizer, which competes with PVG coupled to inductively coupled plasma mass spectrometry (5 ng L−1). Interferences from commonly used inorganic acids (HNO3, HCl and H2SO4) and other elements (As3+, Pb2+, Sb3+, Se4+ and Te4+) were also investigated and the accuracy was verified by analysis of water Standard Reference Material NIST 1643f.

Организация пульсации потока воздуха через теплообменник

In recent years, the enhancement of heat transfer by pulsating flow has become a research hotspot. A great deal of work has been done in the past, with remarkable results, to achieve better heat transfer rates. How to improve the efficiency of heat exchanger is always a research topic. In this paper, pulsating air flow is formed by standard ventilation grille and electric actuator, and the pulsating air flow is guided through two-stage heat exchanger to study the influence of pulsating air flow on heat transfer efficiency. The experimental results show that the heat transfer efficiency can be improved by pulsating flow and the heat recovery efficiency can be reduced by increasing the flow rate of the heating medium.

ОСОБЕННОСТИ РАСПРЕДЕЛЕНИЯ ПОТОКОВ ЖИДКОСТИ В ПЛАСТИНЧАТЫХ ТЕПЛООБМЕННИКАХ

The relevance of the work of information and diagnostic systems in the field of monitoring of plate heat exchange equipment is considered. The reliability of the monitoring devices requires an accurate mathematical description of the thermo hydrodynamic processes in the heat exchange channels. The classical description of these processes implies a uniform distribution of the flow rate of the working medium along the length of the plate package, which in turn implies equal conditions for the formation of salt deposition products on the heating surfaces of the plate heat exchanger. The use of dependencies that take into account the equality of costs for a package of plates reduces the reliability of diagnostics of the efficiency of hot water devices of the plate type. Since the geometric space formed by the plates is represented by parallel channels connected by sections of transit collectors, the method of resistance characteristics is proposed as a method of hydraulic calculation of the distribution features of liquid flows through heat exchange channels. The dependence of the design features of the location of the interplate channels relative to the input of the coolant into the distribution manifold is revealed. It is found that, the flow rate of the circulating coolant is less in the channels most remote from the inlet pipe than in the nearest channels. The hypothesis of the influence of the relative position of the channels in relation to the inlet pipe is confirmed by numerical studies of the hydrodynamic regime of the plate heat exchanger.

Molecular dynamics simulation study on viscosity of silver nanoparticle printing ink

Ink-jet printing and ink direct writing technologies show great advantages in printing electronics and structural customization of flexible materials. The viscosity of the ink will affect the flow rate of the working medium, is an important parameter in the process of deposition. In this paper, the research status of metal particle printing ink and its rheological properties were briefly introduced. Then, water-based silver nanoparticle ink was selected as the research object, and the base liquid system was established with the TIP4P/2005 water model. The shear viscosity of the base liquid was calculated, and the accuracy of the water model in predicting the viscosity was verified. Considering the size of the silver nanoparticles, volume fraction and temperature of the three factors on the viscosity, the effects of the equilibrium molecular dynamics based on Green - Kubo formula viscosity calculation method under different conditions was calculated respectively set shear viscosity of the ink, the conclusion is temperature, volume fraction and particle size on the shear viscosity value, viscosity values associated with negative temperature, volume fraction and the viscosity value is a positive correlation, and particle size has less effect on the viscosity, particle decreases, and the viscosity value increased slightly.

Feasibility study of contrast injection scheme based on body mass and iodine flow rate in coronary computed tomography angiography with wide detector CT

Objective: To investigate the feasibility of coronary computed tomography angiography (CCTA) with the individualized contrast medium injection scheme based on body mass and iodine flow rate by using wide detector CT at 100 kV. Methods: From May 2018 to July 2018,270 patients with clinically suspected coronary artery disease underwent CCTA in TEDA International Cardiovascular Hospital. They were randomly divided into three groups, 90 cases in each group: group A was 0.5 ml/kg, group B was 0.6 ml/kg, the flow rate of contrast medium injection in group A and group B was (body mass×25 mg)/the concentration of contrast medium,group C was 0.8 ml/kg and the flow rate of contrast medium was 5 ml/s. Iohexol (iodine concentration 350 mgI/ml) was used in all three groups. The CT values of the aorta root in the three groups, the CT value of the middle segment of LAD and RCA, SNR、CNR、SD of the aortic root, subjective score of coronary artery and effective dose (ED) were compared. Results: There was no significant difference in CT value of aortic root, CT value of middle LAD and RCA, SNR、CNR、SD of the aortic root, subjective score of coronary artery among group A, group B and group C (all P>0.05). The flow rates of the three groups of contrast agents were statistically different (4.5±0.5 vs 4.5±0.5 vs 5, P=0.015), and there was no statistical difference between group A and group B (P>0.05) but lower than group C (P=0.015); the amount of contrast agent in the three groups was statistically different (32±3 vs 38±4 vs 53±7, P<0.001), group A<B Group<C group; there was no significant difference in ED between the three groups (1.5±0.5 vs 1.5±0.6 vs 1.3±0.6, P=0.613). Conclusions: CCTA imaging with a wide body detector based on a 0.5 ml/kg contrast agent dosage and a flow rate of ((body mass × 25)/350) ml/s individualized injection scheme can ensure the image quality while reducing the total amount of contrast agent and realizing individualized iodine flow rate.

Co-pyrolysis of food waste and wood bark to produce hydrogen with minimizing pollutant emissions

In this study, the co-pyrolysis of food waste with lignocellulosic biomass (wood bark) in a continuous-flow pyrolysis reactor was considered as an effective strategy for the clean disposal and value-added utilization of the biowaste. To achieve this aim, the effects of major co-pyrolysis parameters such as pyrolysis temperature, the flow rate of the pyrolysis medium (nitrogen (N2) gas), and the blending ratio of food waste/wood bark on the yields, compositions, and properties of three-phase pyrolytic products (i.e., non-condensable gases, condensable compounds, and char) were investigated. The temperature and the food waste/wood bark ratio were found to affect the pyrolytic product yields, while the N2 flow rate did not. More non-condensable gases and less char were produced at higher temperatures. For example, as the temperature was increased from 300°C to 700°C, the yield of non-condensable gases increased from 6.3 to 17.5wt%, while the yield of char decreased from 63.6 to 30.6wt% for the co-pyrolysis of food waste and wood bark at a weight ratio of 1:1. Both the highest yield of hydrogen (H2) gas and the most significant suppression of the formation of phenolic and polycyclic aromatic hydrocarbon (PAH) compounds were achieved with a combination of food waste and wood bark at a weight ratio of 1:1at 700°C. The results suggest that the synergetic effect of food waste and lignocellulosic biomass during co-pyrolysis can be exploited to increase the H2 yield while limiting the formation of phenolic compounds and PAH derivatives. This study has also proven the effectiveness of co-pyrolysis as a process for the valorization of biowaste that is produced by agriculture, forestry, and the food industry, while reducing the formation of harmful chemicals.

Performance analysis on a novel photovoltaic-hydrophilic modified tubular seawater desalination (PV-HMTSD) system

To make more effective use of photovoltaic waste heat, a novel photovoltaic-hydrophilic modified tubular seawater desalination system was proposed in this paper. Based on the first and second laws of thermodynamics, energy analysis and exergy analysis models of the system were established. The influences of operation and structure parameters on system performance, heat and exergy losses of each component and performance comparisons among different solar tubular seawater desalination systems were analyzed and discussed. The results manifest that freshwater yield rate, thermal efficiency, energy efficiency and exergy efficiency are enhanced by raising the mass flow rate of working medium and heating pipe length; particularly when the length is small, the increase of heating pipe length can significantly elevate system performance. Moreover, 69.2% of the whole system's heat losses and 90.6% of the whole system's total exergy losses are attributed to the PV module. Compared with other solar tubular seawater desalination systems, the photovoltaic-hydrophilic modified tubular seawater desalination system proposed in this paper has the highest average energy efficiency and exergy efficiency, which are 32.6%, 10.4% respectively. Meanwhile, the photovoltaic thermal collector can provide up to 49.1 W of electricity to maintain the operation of system without consuming extra energy.

Stabilisation and extinction mechanisms of flames in cavity flameholder scramjets

Stabilising a flame in scramjet engines is a current technological challenge. Indeed, the residence time in the combustion chamber is very short, thus limiting the mixing efficiency and consequently, the combustion. This problem is presently addressed by simulating the scramjet combustor of the U.S. Air Force Research Laboratory in which ethylene is injected from the back of a slanted cavity to react with the supersonic airflow. Large-Eddy Simulations (LESs) are performed for different cases showing a dependence of the combustion regimes encountered in the scramjet cavity with the fuel flow rate. For a medium–high flow rate, a mix of lean and rich premixed reaction zones is found along with non-premixed flames. At medium flow rate, rich premixed flames disappear but the flame remains stable in the cavity. The mechanism of flame stabilisation is detailed and the LES tool has proven its efficiency in such challenging configuration. Finally, a mechanism of extinction is proposed when the fuel flow rate is further reduced.

Constructal thermodynamic optimization for dual-pressure organic Rankine cycle in waste heat utilization system

Dual-pressure organic Rankine cycle (DPORC) is a technology with great potential to solve energy problems. This paper performs constructal thermodynamic optimization (CTO) for the DPORC based on a combination of constructal theory and finite-time thermodynamics. The tube outside diameters of the heat exchangers, such as high- and low-temperature evaporators (HTE and LTE) and condenser, and the volume ratio of the high-pressure turbine are the design variables, the system net power output (POW) is the optimization function, and the total volume of the turbines and total heat transfer area (HTA) of the heat exchangers are the constraints. The influences of some parameters, such as the HTA ratios of the HTE and LTE, and the total mass flow rate (MFR) of the working medium on the CTO results are studied. The performance comparison between the DPORC and single-pressure ORC (SPORC) is carried out under the same conditions. The results demonstrate that the system net POWs after the four stepwise CTOs are improved by 1.70%, 3.01%, 5.80% and 8.84% over against the initial system net POW, respectively. Reducing the HTA ratios of the HTE and LTE and increasing the total MFR of the working medium can increase the system net POW. Compared with the performance of the SPORC, the system net POW and system net thermal efficiency of the DPORC are increased by 4.91% and 5.51%, respectively. The optimization results can be used to guide the optimal designs of the low-temperature waste heat utilization systems.