Air Extraction Research Articles

Assessment of the accuracy of open-circuit respiration chambers for measuring enteric methane emissions in cattle

Ruminants are the main source of methane emissions from the agricultural sector. Emission inventories and mitigation strategies require reliable technics of measurement. The respiration chamber methodology is a precise approach for measuring enteric methane emissions in cattle. A set of experiments was carried out to validate two respiration chambers for measuring enteric methane emissions of cattle. The chambers were calibrated considering three main components: the methane analyzer, the air duct and air extraction system, and the chamber itself, by evaluating linearity and response time of the analyzer, plateau variability and high purity methane recoveries in chambers. Recovery test calculations carried out after releasing high purity methane into the chambers gave calibration factors of 0.95 ± 0.05 and 1.03 ± 0.03 for the complete system of respirations chambers one and two, respectively, with corresponding uncertainties of 4.87 and 2.49%. Thus, the respiration chambers for enteric methane measurements of cattle at the University of Yucatan, Mexico function with precision and accuracy. This technique can be used to establish methane inventories and methane mitigation strategies in cattle.

Use of single air extraction and injection to thermodynamically balance the combined heat and mass transfer process

In order to thermodynamically balance the combined heat and mass transfer process at the conditions of unsaturated, saturated and supersaturated state of humid air, measures like single air injection and extraction are implemented to address the distribution of driving forces. From the microscopic point of view, integrated mathematical models for simultaneous heat and mass transfer process are built, coupled with zero, single air extraction and single air injection methods. Off-design analysis for the balance process of driving forces including the heat transfer temperature difference and mass transfer pressure difference are accomplished. The research results exhibit that single air extraction is the preferable measure to lower the total entropy generation in general operating regions for simultaneous heat and mass transfer process (the liquid gas ratio less than 2.9), compared with single air injection. It is found that a minimum value for normalized entropy generation is appeared for all the cases, as the heat capacity rate ratio is unity, and a specific extraction ratio is obtained to minimize the entropy generation with fixed liquid-gas ratio. In addition, it is observed that higher inlet relative humidity will decrease the total normalized entropy generation, while an optimal value is obtained as 0.0064 at inlet relative humidity of 0.85. Meanwhile, inlet relative humidity represents a positive effect on system energy efficiency. It is also confirmed that as the number of extractions is constant and other measures are limited, adjusting the extraction height is an available additional option for further optimizing the thermodynamic performance.

Impact of gas turbine flexibility improvements on combined cycle gas turbine performance

The improvement of gas turbines flexibility has been driven by more use of renewable sources of power due to environmental concerns. There are different approaches to improving gas turbine flexibility, and they have performance implications for the bottoming cycle in the combined cycle gas turbine (CCGT) operation. The CCGT configuration is favourable in generating more power output, due to the higher thermal efficiency that is key to the economic viability of electric utility companies. However, the flexibility benefits obtained in the gas turbine is often not translated to the overall CCGT operation. In this study, the flexibility improvements are the minimum environmental load (MEL) and ramp-up rates, that are facilitated by gas turbine compressor air extraction and injection, respectively. The bottoming cycle has been modelled in this study, based on the detailed cascade approach, also using the exhaust gas conditions of the topping cycle model from recent studies of gas turbine flexibility by the authors. At the design full load, the CCGT performance is verified and subsequent off-design cases from the gas turbine air extraction and injection simulations are replicated for the bottoming cycle. The MEL extension on the gas turbine that brings about a reduction in the engine power output results in a higher steam turbine power output due to higher exhaust gas temperature of the former. This curtails the extended MEL of the CCGT to 19% improvement, as opposed to 34% for the stand-alone gas turbine. For the CCGT ramp-up rate improvement with air injection, a 51% increase was attained. This is 3% points lower than the stand-alone gas turbine, arising from the lower steam turbine ramp-up rate. The study has shown that the flexibility improvements in the topping cycle also apply to the overall CCGT, despite constraints from the bottoming cycle.

Aerodynamic limits of gas turbine compressor during high air offtakes for minimum load extension

Renewable energy sources (RES) have become a favoured alternative to fossil fuel energy generation that has been driven by environmental concerns. Their intermittent nature has meant that gas turbines have remained relevant to support them as a backup. Current grid operation requires gas turbines to operate at as low power as possible when their demand drops, and also ramp-up quickly when power generation from renewables declines. Air extraction from a gas turbine compressor can address the first requirement, as this mechanism reduces the load or power of the engine while storing the air for further pressurised reinjection, related to ramp-up rate improvements. This study demonstrates the aerodynamic implications and the limits to air extraction behind the last stage of the compressor, to achieve further minimum load reduction. To achieve this, a zero-dimensional (0D) analytical model of an engine at design and off-design conditions (air extraction) has been used to determine the boundary conditions for a 3D compressor Computational Fluid Dynamics (CFD) model. The multi-stage CFD model shows the aerodynamic implications of low to high air extractions that are limited by choke, high flow separation, and loss in the pressure at the hub region of OGV and last stage stator. As such, the back of the compressor was more affected than the earlier stages. Based on these, the limit of flow extraction is 18% (of the compressor discharge). The compressor of the analytical engine model showed similarity in trends for comparable conditions with the stand-alone 3D compressor, however, more optimistic than the latter. The work has shown that the compressor is capable of high airflow extractions to reduce the minimum load further.

Preliminary test of a newly developed pilot-scale movable microwave drying equipment for the treatment of solid organic waste

This study introduces a developed, movable, and pilot-scale microwave drying equipment with an automatic control system for the treatment of solid organic waste. Based on a previous study, the structure of the reactor and the arrangement of the magnetron were improved to make the material absorb microwave energy more uniformly and efficiently. The equipment added the auxiliary hot plate and air extraction system, which effectively solved the influence of the occurrence condensate water in the microwave irradiation room on the drying efficiency and energy consumption. The microwave drying behavior of the existing constant-power mode was compared with the improved constant-temperature mode. The experimental results showed that the latter mode could effectively solve the partial overheating of the material caused by uneven heating. The constant-temperature mode was more advantageous in product quality, safety, and selectivity. The advantages and disadvantages of the equipment were analyzed by comparing it with the other existing pilot-scale microwave drying equipment. The proposed system showed good performance. Thus, the newly developed mobile microwave drying system has great potential for practical application.

Design and Performance Analysis of New Ultra-Supercritical Double Reheat Coal-Fired Power Generation Systems

In order to solve the existing problems of large mean heat transfer temperature differences of regenerative air heaters and high superheat degrees of regenerative extraction steam in double reheat coal-fired power generation systems, two new design schemes of ultra-supercritical double reheat cycles are proposed, which can realize the deep boiler-turbine coupling among the heat transfer processes of air, feeding water and regeneration extraction steam on the base of the principle of energy level matching. A typical 1000 MW ultra-supercritical double reheat cycle system is selected as the reference system and the overall system model is built by using the Ebsilon simulation software. The performances of two new systems are analyzed by using both the exergy method and energy equilibrium method. The results show that net output powers of both new systems 1 and 2 increase by 6.38 MW and 6.93 MW, respectively, and the standard coal consumptions of power generation decrease by 1.65 g/kWh and 1.79 g/kWh, respectively. The off-design performances of new systems and the reference system are analyzed, and the results show that performances of two new systems are better than that of the reference system. The system flow of the new system 2 is more complex compared with that of the new system 1. Generally speaking, the performance of new system 1 is better than that of new system 2. On the basis of new system 1, new system 3 is further optimized and its full operating condition performance characteristics are analyzed. The standard coal consumption rate of new system 3 is reduced about 1 g/kWh at higher load, and around 0.2 g/kWh at low load.

Study on Extraction of Cold Air through a Vertical Hole from a Large Snow Mound ― Introduction of experimental formula of αF value and separation of αF value into α and F ―

Study on Extraction of Cold Air through a Vertical Hole from a Large Snow Mound ― Introduction of experimental formula of αF value and separation of αF value into α and F ―

Full-size experimental assessment of the aerodynamic sealing of air curtains for particulate matter

An air curtain is used to ensure an adequate separation between two compartments that is aimed to restrict, a clean one and a contaminated one. The air curtain performance is improved with the use of an air extraction from the “contaminated” compartment. The aerodynamic sealing of an optimized air curtain is assessed regarding particulate matter. The evaluation using visual assessment of the aerodynamic sealing using a cold smoke source is validated against PM 10 detection. It is shown that the air curtain presents a good aerodynamic sealing for the particulate of PM10 and PM2.5 classes and that the visual assessment method can lead to similar results. An equation was obtained with a view to be used to predict the level of aerodynamic sealing of the air curtain when the exhaust rate becomes too low. Another equation was obtained for predicting the average velocity through the door protected by the air curtain required to obtain an aerodynamic sealing, as a function of the jet parameters (nozzle average velocity and thickness). These test results prove that the air curtain, complemented with an air exhaust from the “contaminated compartment”, is suitable to provide an acceptable aerodynamic sealing for the particulate matter. Practical application: The findings of this research are applicable when it is necessary to retain the contamination due to particulate matter using a soft boundary, as air plane jets. This is applicable to medical care centres to reduce the possibility of contamination due to bacteria between different compartments or in pharmaceutical process units to avoid cross contamination among them.

Conventional and Advanced Exergy and Exergoeconomic Analysis of a Spray Drying System: A Case Study of an Instant Coffee Factory in Ecuador

Instant coffee is produced worldwide by spray drying coffee extract on an industrial scale. This production process is energy intensive, 70% of the operational costs are due to energy requirements. This study aims to identify the potential for energy and cost improvements by performing a conventional and advanced exergy and exergoeconomic analysis to an industrial-scale spray drying process for the production of instant coffee, using actual operational data. The study analyzed the steam generation unit, the air and coffee extract preheater, the drying section, and the final post treatment process. The performance parameters such as exergetic efficiency, exergoeconomic factor, and avoidable investment cost rate for each individual component were determined. The overall energy and exergy efficiencies of the spray drying system are 67.6% and 30.6%, respectively. The highest rate of exergy destruction is located in the boiler, which amounts to 543 kW. However, the advanced exergoeconomic analysis shows that the highest exergy destruction cost rates are located in the spray dryer and the air heat exchanger (106.9 $/h and 60.5 $/h, respectively), of which 47.7% and 3.8%, respectively, are avoidable. Accordingly, any process improvement should focus on the exergoeconomic optimization of the spray dryer.

Hot air extraction to improve aerodynamic and heat transfer performances of natural draft dry cooling system

A large amount of hot air in dry cooling tower of natural draft dry cooling system can be recovered for many applications, such as the boiler air supply and feed water preheating in power plants. However, the hot air extraction will definitely affect the aerodynamic characteristics of dry cooling tower and heat transfer performance of air-cooled heat exchanger. In this work, the impacts of hot air recovery on the thermo-flow performances of natural draft dry cooling system under crosswind conditions are investigated. The variable fields are presented and the outlet water temperature of air-cooled heat exchanger is calculated with the wind speed, the mass flow rate of recovered hot air and the height of hot air extractions considered. Finally, the turbine backpressure and power consumption of induced fans are compared to evaluate the overall cooling effect of dry cooling system with hot air extractions. The results show that hot air extraction is favorable for the cooling performance of natural draft dry cooling system, and the higher mass flow rate of recovered hot air leads to a stronger cooling capability. The hot air extractions are proposed to set near the tower inlet with the turbine backpressure most reduced by 9.28%, which can contribute to the design and operation of natural draft dry cooling system in need of energy conservation.

A novel method for pre-ventilation of shipping containers.

Numerous shipping containers arrive with high levels of hazardous volatile chemicals in the interior air. This may constitute a health risk during inspection and unstuffing. The problem remains largely unaddressed due to ignorance, lack of suitable field instruments for chemical identification, and lack of easy to use, effective ventilation methods. Here, we present a novel ventilation approach based on extraction of air from the closed container via the existing top corner ventilators. A suction plate was developed to fit tightly over the corner ventilator and connected with a flexible hose to an extraction fan. Air flow rates and vacuum under the plate were measured in the lab with five different types of extraction fans. The vacuum produced under the suction plate held it securely in place. Washout of air contaminants under different configurations and ventilation scenarios was studied in an experimental 20-ft container stuffed with acetone emitting cardboard boxes and in the field with containers stuffed with commercial goods. Volatiles in container air were continuously recorded with logging photoionization detectors in various positions before, during and after ventilation. A maximum air flow through the ventilator of 186m3/h was achieved. At 100m3/h, the initial acetone levels were reduced to 11% and 4.9% in the tightly stuffed and to 6.0% and 3.1% in the loosely stuffed (pallets) experimental container after 1h and 4h, respectively, as measured inside the closed door (mean values). As expected, the washout was somewhat slower in nine 40-ft field containers and reached 22% and 11%, respectively. In both experimental and field containers the concentration rose quickly when ventilation ceased. In conclusion, the new ventilation method allows for convenient, safe and efficient ventilation of risk containers. The container should be continuously ventilated until it is opened, or rapid re-accumulation of volatiles will occur.

Anti-Fungal Properties of Ficus exasperata, Jathropha curcas and Mangifera indica on Fusarium oxysporium Causing Seed Rot and Seedling Blight in Soybean

Soybean is affected by a wide range of diseases, many of which are seed-borne. In vitro and in vivo studies were conducted on the control of Fusarium oxysporium the causal pathogen of soybean seed rot using three plant leaf extracts. Laboratory experiments were conducted with aqueous extracts of air dried leaves of Ficus exasperata, Jatropha curcas, and Mangifera indica and a synthetic fungicide Mancozeb. Using the poisoned food technique, various concentrations (20, 40, and 60%) of the leaf extracts and Mancozeb (0.002%) utilized inhibited the mycelial growth of the pathogens in vitro. Effects of Mancozeb comparative to the plant extracts were determined. Even though all the extracts showed varying degrees of antifungal efficacy, 60% concentration of F. exasperata had the highest level of inhibition (64.52%) on the mycelial growth of the pathogen and was significantly different (P≤0.05) from Mancozeb (83.86%) after 3 days. Extracts of J. curcas and M. indica showed a lower inhibition level ranging from 54.80% to 18.56% and 54% to 22.59% respectively, which were significantly lower in comparison to Mancozeb (P≤0.05). Inhibition of fungal growth increased with a corresponding increase in extract concentration and days. The plant leaf extracts effectively inhibited mycelial growth of the pathogen in vitro after 3 days. The efficacy of seed treatments against seedborne F. oxysporium were evaluated under greenhouse conditions at 40 and 60% concentrations. The result indicated that seeds of various soybean varieties (TGX1448, TGX1987- 10F, TGX 1988-5F) treated with 60% concentration of F. exasperata performed better than the others and improved seed germination: 33.33% in TGX1448 and TGX1987-10F and 26.67% in TGX 1988-5F. The number of leaves was 4.33, 5.0 and 3.67 in TGX1448, TGX1987-10F, TGX 1988-5F respectively; while stem length was 18.33cm, 18.67cm, 15.00cm respectively, in the above order. However, the results were lower and statistically different (P≤0.05) from Mancozeb and the uninoculated control. The results obtained in this study confirmed that Jathropha curcas, Ficus exasperata, and Mangifera indica possess potential inhibitory effect on Fusarium oxysporium, one of the causal agents of Soybean seed rot and seedling blight.

Control of temperature and fume generation by cooking in a residential kitchen by ceiling radiative cooling and fume hood extraction

The heat radiation in a residential kitchen was simulated by CFD (Computational-fluid-dynamics) to evaluate the cooling by a radiant cooling ceiling panel and pollution dispersion by the range hood and the air extraction system. The kitchen has a 2-hobs stove and a fume hood for removing waste heat and fumes. The simulation was validated by measurements in a domestic kitchen in a home in Changsha, China, where summer temperature is generally about 33 °C and often over 35–42°C. The simulation results show that the pollutant concentration in the kitchen during cooking was much lower than the Chinese standard criteria of GB/T18883-2002. A standard turbulence model was used, which indicated satisfactory distribution of temperature and airflow in the kitchen. The indoor airflow velocity was low. The airflow temperature when both hobs were used was slightly higher by 3–4°C than when a single hob was used. The temperature in the kitchen during cooking was about 28 °C, which was a degree lower than the living-room temperature, thus maintaining a comfortable thermal and healthy environment. The radiant cooling in the ceiling was shown to be a significant contributing factor. The ring suction type range hood has a sufficient capacity to remove the kitchen fume contaminants.

Gas turbine minimum environmental load extension with compressed air extraction for storage

The fact that most renewable forms of energy are not available on-demand and are typically characterised by intermittent generation currently makes gas turbine engines an important source of back-up power. This study focuses on one of the capabilities that ensure that gas turbines are more flexible on the electric power grid. The capability here is the minimum environmental load that makes it possible to keep a gas turbine engine on the grid without a shut-down, to offer grid stability, adding inertia to the grid in periods when there is no demand for peak power from the engine. It is then desirable to operate the engine at the lowest possible load, without infringing on carbon monoxide emissions that becomes dominant. This paper demonstrates this potential through the extraction of the pressurised air from the back end of the compressor into an assumed energy storage system. The simulation of the engine performance using an in-house tool shows the additional reduction of the power output when the maximum closing of variable inlet guide vane is complemented with air extractions. However, the identified key strategy for achieving a lower environmental load (with same carbon monoxide emission limit) is to always maintain the design flame temperature. This is contrary to the conventional approach that involves a decrease in such temperatures. Here, a 34% reduction in load was achieved with 24% of flow extraction. This is shown to vary with ambient temperatures, in favour of lower temperatures when the combustor inlet pressures are higher. The emission models applied were based on empirical correlations and shows that higher combustor inlet pressures, high but constant flame temperatures with core flow reduction is crucial to obtaining a low environmentally compliant load. The compressor analysis shows that choking is a noticeable effect at a higher rate of extractions; this is found to occur at the stages closest to the extraction location.

Erosion Damage to Impeller of Welding Fume Extraction System

Abstract Even very simple cases of component failure can represent an enrichment for this section Failure Analysis. Besides the instructive value of an easily understandable content, they allow those failure analysts becoming acquainted with the field to gradually get to know the most important material-related mechanisms governing component failure cases. A look back by the authors on the section Failure Analysis of Practical Metallography cases revealed only one single erosion failure case in the past 10 years. It won't therefore do any harm to address this interesting failure mechanism once again. The erosion failure of a fan impeller presented in this article was very easily solved However, it was rather unexpected. Who would have considered it possible that an air extraction system in a factory workshop is subject to such high erosive distress? Hence, the main message of this short article is that the experts tasked with investigating the component failures should be very thorough and propose all sorts of damage hypotheses, sometimes even those which, at first glance, appear unlikely, and may only reject them when the examination results indicate the contrary.

Simulation of the distribution of air flows and fuel combustion products in a channel of a tunnel kiln

A characteristic problem of the operation of tunnel kilns with high overlap is the output of products with low quality and a decrease in the energy efficiency of the burning process as a whole. Therefore, the object of research is the process of the flow of kiln gases through the channel of the tunnel kiln, the change in velocity of which was studied depending on the geometric parameters of the tunnel.In the course of studies of the dependence of the velocity distribution of the flow of kiln gases along the channel of the kiln on its geometric characteristics, a numerical simulation method in a simplified 2D formulation using the OpenFoam open code using the k--shear stress turbulence model is used. The velocity fields of kiln gases are obtained for three options for the height of the channel: the base with a vault height of 2 m, with a reduced vault height along the entire length of the tunnel and with a reduced tunnel height only in the burning zone. Analysis of changes in flow rates shows that the most effective would be to reduce the height along the entire kiln length, while changing the arch height in the burning zone will hardly affect the uniformity of velocities in the heating zone. Reducing the arch height also minimizes the likelihood of a return air flow in the cooling zone in the area from burning to the place of air extraction for drying. A lower overlap in the cooling section will increase the intensity of heat removal and, accordingly, reduce its loss with the product in order to use it for drying products.The presented simulation results make it possible to note that a change in the height of the overlap will lead to an increase in aerodynamic drag and, consequently, a pressure drop. This will require additional energy costs for driving draft engines and the possibility of increasing temperatures in the space under the cars.

Antimicrobial, Phytochemical Analysis and Molecular Docking (In-silico Approach) of Tithonia diversifolia (Hemsl.) A. Gray and Jatropha gossypiifolia L on Selected Clinical and Multi-Drug Resistant Isolates

The aim of this study is to determine the zones of inhibition, phytochemical screening and molecular docking (In-silico Approach) of Tithonia diversifolia (Hemsl.) A. Gray and Jatropha gossypiifolia L against selected clinical and multi drug resistant isolates. Crude extraction of air dried leaves were carried out by soaking the plant in ethanol and ethyl acetate, standard agar diffusion method was used for sensitivity testing, minimum inhibitory concentration and minimum bactericidal concentration values were obtained by agar dilution method. The antimicrobial activity of the leaf extracts of T. diversifolia (Hemsl.) A. Gray and J. gossypiifolia L was assayed against Bacillus subtilis, Escherichia coli, Klebsiella pneumonia, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysentriae, Staphylococcus aureus, Streptococcus pyogenes, Candida albican and against multi drug resistant bacteria which are Acinetobacter baumannii, Enterobacter agglomerans, Proteus mirabilis, Providencia stuartii, Salmonella subsp 3b. Levofloxacin and fluconazole were the standard antibiotics used. Sensitivity test revealed the highest zone of inhibition observed for J. gossypiifolia L and T. diversifolia (Hemsl.) A. Gray against Candida albican with mean and standard deviation of 29±1.414 and 19.5±0.707 at 100 mg/ml respectively, while the least zone of inhibition was observed from the extracts of J. gossypiifolia L against Escherichia coli with 11.75±0.354 at 100 mg/ml. Both plant extracts showed antimicrobial activity against multi drug resistant isolates having zones of inhibition ranging from 0 to 15±1.414. The Minimum Inhibitory Concentration of the extracts ranges between 6.25 and 100 mg/ml as well as the Minimum Bactericidal Concentration. The qualitative and quantitative phytochemical analysis showed the presence of alkaloids, anthraquinone, cardiac glycosides, flavonoids, phlobotannins, reducing sugars saponins, steroids and tannins. Molecular docking of the phytochemicals of T. diversifolia (Hemsl.) A. Gray only was carried out using levofloxacin as template, which revealed the presence of compounds more effective in inhibiting DNA gyrase enzyme. Thus, the use of both plants as traditional medicine is justifiable and should be encouraged in the formulation and production of new antibiotics.

Antioxidant Potential of Morinda Lucida and Psidium Guajava Extracts and Actions Against Paracetamol- Induced Kidney and Liver Injuries in Rats

Antioxidant agents of plants origin have continued to attract interest because of the potential they hold in the maintenance of human health accompany with their minimal side effects. The present study sought to evaluate the comparative free radical scavenging activities of ethanol extracts of air dried Morinda lucida leaves (EMLL) and Psidium guajava leaves (EPGL) by measuring their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, nitric oxide (NOˉ) radical, 2,2 azinobis-( 3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*), and inhibit lipid peroxidation (LPO). Antioxidant activities of the extracts were also determined in the plasma of the rats fed with the extracts by assaying for antiradical activity against DPPH and NO radicals in vitro. In vivo antioxidant effects of the extracts were also evaluated in paracetamol treated rats. Twenty rats were randomly divided into four groups for this study. Group 1 received normal feed as control, group 2 received 14.30mg/kg b.w of paracetamol by gavage, groups 3 and 4 received 400mg/kg b.w of EMLL and EPGL each for 7 days plus paracetamol on the 8th day respectively. Catalase (CAT) and superoxide dismutase (SOD) activities and malondialdehyde (MDA) status were assayed for in the kidney, liver and serum. Histopathological examinations of liver and kidney were also carried out. The results showed that EMLL and EPGL exhibited free radical scavenging ability in dose dependent manner towards DPPH, NO, ABTS radicals as well as inhibition of LPO. The results of evaluation of the antioxidant potentials of the extracts while in the plasma showed that they were associated with free radical scavenging activity in vivo. Paracetamol treatment caused significant (p<0.05) decreases in SOD and CAT activities, and marked increase (p<0.05) in MDA levels when compared with the control. However, compared with paracetamol only group, the extracts caused significant (p<0.05) increase in SOD and CAT activities and decreased MDA levels. Histopathological analysis of kidney and liver showed that the extracts were able to offer protection against paracetamol-induced kidney and liver injuries. The extracts therefore have strong antioxidant and cytoprotection abilities.

Antioxidant Potential of Morinda Lucida and Psidium Guajava Extracts and Actions Against Paracetamol- Induced Kidney and Liver Injuries in Rats

Antioxidant agents of plants origin have continued to attract interest because of the potential they hold in the maintenance of human health accompany with their minimal side effects. The present study sought to evaluate the comparative free radical scavenging activities of ethanol extracts of air dried Morinda lucida leaves (EMLL) and Psidium guajava leaves (EPGL) by measuring their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, nitric oxide (NOˉ) radical, 2,2 azinobis-( 3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*), and inhibit lipid peroxidation (LPO). Antioxidant activities of the extracts were also determined in the plasma of the rats fed with the extracts by assaying for antiradical activity against DPPH and NO radicals in vitro. In vivo antioxidant effects of the extracts were also evaluated in paracetamol treated rats. Twenty rats were randomly divided into four groups for this study. Group 1 received normal feed as control, group 2 received 14.30mg/kg b.w of paracetamol by gavage, groups 3 and 4 received 400mg/kg b.w of EMLL and EPGL each for 7 days plus paracetamol on the 8th day respectively. Catalase (CAT) and superoxide dismutase (SOD) activities and malondialdehyde (MDA) status were assayed for in the kidney, liver and serum. Histopathological examinations of liver and kidney were also carried out. The results showed that EMLL and EPGL exhibited free radical scavenging ability in dose dependent manner towards DPPH, NO, ABTS radicals as well as inhibition of LPO. The results of evaluation of the antioxidant potentials of the extracts while in the plasma showed that they were associated with free radical scavenging activity in vivo. Paracetamol treatment caused significant (p<0.05) decreases in SOD and CAT activities, and marked increase (p<0.05) in MDA levels when compared with the control. However, compared with paracetamol only group, the extracts caused significant (p<0.05) increase in SOD and CAT activities and decreased MDA levels. Histopathological analysis of kidney and liver showed that the extracts were able to offer protection against paracetamol-induced kidney and liver injuries. The extracts therefore have strong antioxidant and cytoprotection abilities.

Performance of gas turbine multi generation system regulated with compressor bypass extraction air energy storage

In aim to improve system efficiency and flexibility at deep peak-load operation, a novel supply-side load regulation strategy was proposed for gas turbine-based CCHP (combined cooling, heating and power) systems, where the load was regulated through compressor bypass air extraction (CBAE) for energy storage in addition to inlet guide vane (IGV) regulation strategy. The part-load performance of gas turbine with CBAE was studied and compared with the performance under IGV regulation strategy; as well, the supply-demand coupling performance of the proposed CCHP system was investigated in three different scenarios of demand-side load distributions. Taking maximum overall energy efficiency as the optimization target, the design capacity of the proposed system was optimized and analyzed. The analysis indicates that, gas turbine part-load power efficiency under CBAE regulation is inferior to that under IGV regulation, whereas the former ensures gas turbine a higher capacity of power and heating than the latter. CBAE regulation strategy greatly improves heat-power ratio and enhances load adaptability. The case study shows that at a higher heat-power ratio, the overall energy efficiency of the proposed system is 1.75% greater, while the optimal capacity of gas turbine is 8.64% lower than that of the reference one.