Maximum Average Efficiency Research Articles

Assessment of a NaOH-based alkaline electrolyser’s performance: System modelling and operating parameters optimisation

Most of the scientific research is focused on KOH-based alkaline electrolysers, while NaOH-based ones are unexplored although they present interesting features. This paper presents a semi-empirical model developed in the Python environment to predict a NaOH-based alkaline electrolyser’s performance to cover such a research gap and perform an optimisation procedure of electrochemical parameters. A sensitivity analysis has been carried out to study how its performance changes while varying the: i) NaOH content, ii) pressure, and iii) both. Separately, the best result has been obtained with a NaOH content and an operating pressure of 8% and 6.5 bar, respectively. Furthermore, the same values have been recorded even by varying both the NaOH content and the operating pressure. Specifically, a maximum average efficiency increase of 3.57% at 35°C, 0.17% at 40 °C, and 3.74% at 35°C in the case of NaOH content, pressure, and both, respectively.

Design method based on a new slip-diffusion parameter of centrifugal pump for multiple conditions in wide operation region

Centrifugal pumps are widely used in industrial production, agricultural irrigation, water transportation, energy storage pump station and ocean engineering, and the development prospect of centrifugal pump is to work in a wide operation region with high efficiency. In this work, the achievement of high-efficiency operation for multiple conditions in a wide operation region is strenuously realized by a new design method from the perspective of flow mechanism analysis and theoretical derivation. A new dimensionless slip-diffusion parameter Φ on consideration of the slip effect and diffusion effect in impeller is proposed. On the basis of the new parameter Φ, a new design method of centrifugal pump is established to improve the pump efficiency for multiple conditions in a wide region. Two centrifugal pumps with different specific speeds of 102 and 127 are designed to validate the proposed design method. When the slip-diffusion parameter Φ ≈ 0.677, the centrifugal pump can achieve the maximum average efficiency for multiple conditions. For Φ < 0.677, the pump efficiency rapidly drops at the high flow rate region. For Φ > 0.677, the pump efficiency rapidly drops at the low flow rate region. Two centrifugal pumps are numerically simulated to obtain the flow pattern, and the entropy production method is used to analyze the relationship between flow field and energy performance of the pumps. Entropy production mainly appears at the blade suction side and the impeller outlet. For different flow rates, the total entropy productions of pumps with Φ ≈ 0.677 are always the minimum.

Effect of an Exhaust Heat Exchanger with Inserts on the Performance of Thermoelectric Generators

A thermoelectric generator is used as a waste heat recovery system for generating electric power. The thermoelectric generator system consists of an exhaust heat exchanger, a thermoelectric module, and a water heat exchanger. The aim of the current work is to explore different types of inserts used in the test section of the exhaust heat exchanger and power generation of thermoelectric generators at different operating conditions. An experimental setup has been developed for conducting experimental investigation on thermoelectric generators to find the effect of the exhaust heat exchanger (EHE) with inserts on the performance of thermoelectric generators. The cone (G-type test section) and cone-cylinder (H-type test section) type inserts were introduced to enhance the performance of the thermoelectric generator. Compared with an insert-free (empty, F-type) thermoelectric generator with cone and cone-cylinder type inserts in terms of the output power, the average heat transfer rate and convection heat transfer coefficient of F-type, G-type, and H-type test sections of the EHE are 358, 468, and 459 W and 76, 100, and 97 W/m2K, respectively. It shows that the G-type test section of EHE exchanges more heat from engine exhaust to the hot surface of the thermoelectric module through the wall of the EHE. The G-type test section created more temperature difference; obviously, it generated more power output. It was observed that the G-type and H-type test sections of exhaust heat exchangers improved average maximum output power by 29.49% and 26.11% than that by the F-type test section of heat exchanger, respectively. The F-type, G-type, and H-type test sections of exhaust heat exchangers showed a maximum average efficiency of 0.80, 0.78, and 0.70%, respectively.

Istraživanje efikasnosti krojne slike korišćenjem odevnih predmeta različitih veličina i materijala različitih širina

Marker efficiency is a very important term in garment industry. We all know that in cutting section of garment industry there is a high possibility of fabric wastage. And with the high marker efficiency we can decrease the wastage. And obviously the lower wastage will secure the loss of time and money. In the garment industries marker planning is done with a single marker width with single size set ratio. But, variable marker width with variable size ratio can be used for maximum marker efficiency. By using variable marker width and variable size set we wanted to maximize the marker efficiency in this research. After getting the maximum average efficiency it was found more efficient than the factory for a particular style. This will help in achieving more profit and loose wastage. We here increased the marker efficiency by 6.01% more than the Factory efficiency and by which we decreased a huge amount of fabric wastage besides getting more profit than before.

The cross-efficiency evaluation model with judgmental information: Cooperative game and optimal coordination perspective

In the actual efficiency evaluation process, it frequently occurs that the quantitative input and output data of each decision-making unit is difficult to obtain due to the limitation in data measurement and the absence of prior information. Instead, the form of judgment information can be selected to express the input–output state of the evaluated decision-making units compared with the reference level. Traditional cross-efficiency evaluation methods do not involve this case and cannot be well used in this situation. Based on the above problems, a multiplicative cross-efficiency evaluation model with judgmental information is constructed, and the optimal adjustment model is provided by introducing deviation variables to deal with the inconsistent issue of data features. In addition, for the case of multiple optimal solutions, the maximizing and minimizing secondary objective models of the multiplicative cross-efficiency are established respectively to reasonably identify the corresponding optimal weights. Simultaneously, in order to effectively depict the interaction between decision-making units, the characteristic functions of JM-cross efficiency cooperative game and the multiplicative Shapley value are established based on benevolent and aggressive cross-efficiency matrices. Moreover, in order to avoid the extreme ranking results that are oriented by high impact decision-making units, a series of optimization coordination models are developed, and an optimal efficiency ranking vector generation method with strong applicability and decision flexibility is proposed. The optimal efficiency ranking vector not only creates a precise match with the given Shapley index of the multiplicative cross-efficiency game, but also bounds between the minimum and the maximum average efficiency. Finally, the validity and rationality of the discussed models are illustrated by a concrete example.

Optimal adjustment of mine fan geometry and operation

Mine fans consume significant electrical power, so it is important to ensure high efficiency of their operation. The aim of this study is to develop a method to determine the most economically efficient method to adjust axial fan geometry and operation at the maximum average efficiency in all operating modes. The method includes a developed mathematical model of the single-stage axial fan duty and a genetic algorithm for optimizing the fan parameters. The initial data for the mathematical model were the geometry of the fan blades of the average radius and the parameters of the fan operating mode. The result of the calculation was the fan efficiency in a preset operating mode. Two adjustment scenarios are modeled: fans with variable pitch blades and fans with variable rotation speed. The fan efficiency was determined by calculating the total pressure loss at the unit stage at the middle radius with regard to the loss at the blade tips. Since the mathematical model contains a large number of independent parameters, and there exists the possibility of local extrema, the optimization is performed using the genetic algorithm. The mathematical model of the fan with variable pitch blades was tested using experimental data. The error of the mathematical model in continuous modes at high efficiency (&gt;75%) never exceeds 1.5%. As a case-study, the optimal fan parameters are determined for two preset operating modes and for two adjustment scenarios of fans with variable pitch blades and with variable rotation speed. On the basis of the obtained geometric parameters at the average radius of blades, using the constant circulation law, the fan designs were developed and then investigated by numerical simulation in CFX program. It is shown that if the air flow rate in operating modes differs significantly and the pressure is not, it is advisable to use fans with variable pitch blades.

DAB Converter for EV Onboard Chargers Using Bare-Die SiC MOSFETs and Leakage-Integrated Planar Transformer

This article discusses electrical design optimization of a 3.3 kW, 380 V to 250–380 V, 500 kHz, dual-active-bridge dc–dc converter for onboard chargers, operated with constant-power (CP) charging. In order to operate the converter at 500 kHz without concerns on switching performance and efficiency while also improving power density, a low-parasitics, PCB-based, wire-bondless full-bridge module featuring bare-die SiC MOSFETs and compact, electrothermally multifunctional coolers is employed. High switching frequency operation also felicitates the realization of the DAB inductor using the transformer’s leakage inductance, thereby enhancing the power density by eliminating the need for a discrete inductor. Design strategy for such magnetic integration in a planar transformer is discussed, followed by a systematic design optimization of the transformer, including the selection of leakage inductance value, the core geometry, and the number of turns for achieving zero-voltage switching (ZVS) and maximum average efficiency over the entire charging profile. Experimental validation was performed using a proof-of-concept prototype, which is operated up to 3.3 kW and has a final projected power density of 5.44 kW/L. Results demonstrate the operation with ZVS over the entire charging profile with satisfactory high-frequency waveforms and a peak efficiency of 98%.

Anaerobic Treatment for Palm Oil Mill Effluent Using Covered In-the Ground Anaerobic Reactor (CIGAR)

Wastewater from crude palm oil mills contains high organic matter, which potentially produces biogas through anaerobic digestion processes. The design and operation of an anaerobic bioreactor require a good understanding of the reaction kinetic in the bioreactor. This study aimed to evaluate the biogas production from POME and to determine the kinetic parameters of microbial growth and the substrate utilization rates in a CIGAR. An experiment was conducted using a 5-m3 bioreactor with a working volume of 4.4 m3. Wastewater from the Bekri palm oil mill was stored in a 5-m3 tank. After stabilization, the wastewater was loaded into the reactor at a rate of 100 to 250 L/d, corresponding to a COD loading rate of 1.373-3.097 kg·m-3.d-1, and an HRT of 18-44 days. Monod, Contois, Moser, and Shuler kinetic models were evaluated. The results showed that the Shuler model performed best for microbial activities, while the first order reaction model performed best for the substrate utilization kinetic. The maximum specific growth rate (μmax) for the Shuler model was 0.052 d-1 and the saturation constant (Kso) was 0.119. The maximum substrate utilization rate constant (ks) was 2.183 d-1 and biomass yield (Yx/s) 0.024 kg/kg. The maximum average efficiency of anaerobic degradation (34.4%) occurred at a feeding rate of 100 L/d with methane yield of 0.120 Nm3/kg of removed COD. This value is relatively low compared to the maximum potential of 0.350 Nm3/kg CODr.

The integration of solid-solid phase change material with micro-channel flat plate heat pipe-based BIPV/T

In this paper, the influence of the solid-solid phase change material on the novel micro-channel flat-plate heat-pipe–based building integrated photovoltaic/thermal system has been investigated, which has been expected to store the excess heat, enhance the overall efficiency of the system and maintain the stable photovoltaic temperatures. The proposed system was divided into two parts, i.e. the outdoor part formed by flat-plate glass, photovoltaic panel, micro-channel flat-plate heat pipes, solid-solid phase change material layer and insulated material, and indoor part including the storage tank, water pump and storage batter. The experiments were conducted at the Guangdong University of Technology, China, to investigate the thermal and electrical performance of the proposed system. When the simulated radiation was at 300 W/m2 and water flow rate was at 600 L/h, the maximum average thermal, electrical and overall efficiency were found at 52.9%, 7.9% and 60.8%, respectively, when the xenon lamps were turned on, and the maximum average efficiency of 86.6% were found when the xenon lamps were turned off, indicating the most appropriate working condition of the proposed system due to the thermal storage and release of the solid-solid phase change material during the system operation. Compared with the previous studies of the conventional building integrated photovoltaic/thermal systems, it was found that the overall efficiency of the system averagely increased 5–30% and the daily water temperature difference of the system averagely increased 1.8–10.5℃, indicating that the solid-solid phase change material can significantly increase the thermal efficiency of the system. Practical application The proposed micro-channel-flat-plate-heat pipe based BIPV/T (MCFPHP-BIPV/T) system with SS-PCM will be potentially used in buildings to provide amount of electricity and thermal energy. The generated electricity will be used by the residential electrical devices or connected to the grid, and the thermal energy can be used for hot water, even for space heating and cooling. The proposed building-integrated system can be assisted in realising the targets of energy saving and carbon-emission-reduction in buildings.

Enhanced ionization efficiency in TIMS analyses of plutonium and americium using porous ion emitters

Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) using porous ion emitter (PIE) techniques for the analyses of trace quantities of americium and plutonium were performed. Repeat ionization efficiency (i.e., the ratio of ions detected to atoms loaded on the filament) measurements were conducted on sample sizes ranging from 10–100pg for americium and 1–100pg for plutonium using PIE and traditional (i.e., a single, zone-refined rhenium, flat filament ribbon with a carbon ionization enhancer) TIMS filament sources. When compared to traditional filaments, PIEs exhibited an average boost in ionization efficiency of ∼550% for plutonium and ∼1100% for americium. A maximum average efficiency of 1.09% was observed at a 1pg plutonium sample loading using PIEs. Supplementary trials were conducted using newly developed platinum PIEs to analyze 10pg mass loadings of plutonium. Platinum PIEs exhibited an additional ∼134% boost in ion yield over standard PIEs and ∼736% over traditional filaments at the same sample loading level.

Nonbinary variance-balanced designs–part I, optimality

Let D(v,b,k) be a class of designs with ν treatments and b blocks, each of size k. We show that (i) if a variance-balanced design exists in D(v, b, k), then it is E-optimal. Let Δ(ν, b, k) ⊂ D(v, b, k) containing all the variance-balanced designs. Then we prove that (ii) a design d ∈′ Δ(ν, b,k) is ER-optimal in Δ(ν, b,k) if its replication numbers are as uniform as possible, (iii) a design d in Δ(ν, b,k) is AR-optimal and DR-optimal in Δ(ν, b, k) if its replication numbers are all equal except one, and (iv) a design d in Δ(ν, b, k) has maximum average efficiency in Δ(ν, b,k) if its replications numbers are all equal but one. Average efficiencies of designs in three classes are computed and tabulated at the end.

Thermal analysis on charging and discharging behaviour of a phase change material-based evacuated tube solar air collector

The performance analysis on the phase change material-based evacuated tube solar air collector was examined under consecutive and simultaneous charging and discharging modes. Acetamide was used as phase change material. The system performance was evaluated on the basis of the phase change material storage system energy efficiency, exergy efficiency, collector efficiency, the instantaneous energy stored in the phase change material and total energy stored by the system at low and high air flow rates of 0.018 kg/s and 0.035 kg/s, respectively. The maximum average efficiency (17.9%) of the collector was obtained at a high air flow rate during simultaneously charging and discharging of the phase change material. The results obtained demonstrate that the system is more effective when it is operated with high air flow rate during simultaneously charging and discharging of the phase change material. The average total energy at high air flow rates is 1.01 to 1.02 times more in comparison to that at low air flow rates. The findings show the feasibility of the phase change material-based evacuated tube solar air collector for producing hot air for space heating during consecutive and simultaneous charging and discharging of the phase change material in northen Indian climatic conditions. This system would be relevant in areas with good sunlight.

Evaluation of the economic viability of the application of a trigeneration system in a small hotel

Energy is an indispensable factor for any human activity. Transport, industrial production, trade, communications, etc. depend on the energy availability. Traditionally, consumers meet their energy demand by buying separately electricity and fuel to the distribution companies. With regard to electric energy generation acquired by consumers, a good portion is produced in conventional thermoelectric power plants. In modern power plants, the total losses in energy can go up to 52.5 % without any kind of recovery. Thermal energy is obtained from the fuel purchased by consumers in burning systems with a maximum average efficiency, at best, about 90 % (10 % lost). Faced with this problem arises the need to increase the efficiency of electricity production processes and heat generation in order to reduce the financial and environmental costs. Thus, as an alternative to large conventional power plants, decentralized production of electricity arises, and, in particular cogeneration, in order to take advantage of the inherent limitations of the conversion of heat into work. CHP (Combined Heat and Power) is a combined process of production and exploitation of thermal energy and electricity, in an integrated system, from the same primary source. In spite of not being a new technology its applications are mainly used in the industry. These kind of systems contributes also for a decrease of CO2 emissions to the environment. The aim of this study is to analyse the technical and economic potential of a real situation in a small hotel located in a city of Portugal. Instead of using only a CHP, the generated heat was also used for cooling - CHCP (Combined Heat, Cooling and Power). For that, besides the energetic analysis carried out, a detailed economic analysis was done in order to evaluate its feasibility and risk regarding the main parameters to be taken in account, namely the NPV (Net Present Value), IRR (Internal Rate of Return), Payback Period and PES (Primary Energy Savings) and Avoided Emissions (AE) of CO2. The main conclusions obtained are that the CHCP contributes to a PES of 57 tep/year, the AE being 68 teq CO2/year. The payback period is 3.6 years.

A novel twin-rotor radial-inflow air turbine for oscillating-water-column wave energy converters

A novel air turbine for bidirectional flows in oscillating-water-column wave energy converters is presented and its performance is analyzed. The turbine is based on a pair of conventional radial-inflow rotors mounted on the same shaft, complemented by the corresponding guide vane rows, by a curved-duct manifold arranged circumferentially in a period manner and by a two-position cylindrical valve. Numerical values of the performance of the whole machine were obtained from published experimental data of the flow through a conventional radial-inflow gas turbine, together with CFD (computational fluid dynamics) results for aerodynamic losses in the curved duct manifold. Four different geometries, combined with five different sizes, of the curved-duct manifold were numerically simulated. Windage losses, that occur at the inactive rotor and are inherent to the machine conception, were found to be a major loss. A peak value of about 86% was obtained for the overall efficiency of the machine. Comparisons are presented between the new turbine and the biradial turbine (sliding guide-vanes version), the latter being possibly the most efficient self-rectifying turbine model-tested so far. The new turbine was found to be more efficient, both in peak instantaneous efficiency and in maximum average efficiency in random waves, by a margin of about 8%.

A digital predistortion assisted hybrid supply modulator for envelope tracking power amplifiers

In this paper, a novel digital predistortion assisted supply modulator is presented. The proposed modulator is suitable for envelope tracking power amplifiers. In this topology, a digitally controlled linear power amplifier is used to compensate the switching noise ripples of the switching modulator. The proposed structure is evaluated with a 0.18µm CMOS process technology. The results show up to 9% static efficiency improvement in comparison with previous one-phase and two-phase architectures. It is shown that for a 5MHz WiMAX signal with a 6.7dB PAPR at 26.8dBm output power, a maximum average efficiency of 73.5% is achieved in the proposed design.

EXPERIMENTS ON HYDRODYNAMIC PERFORMANCE OF WEIS–FOGH-TYPE WATER TURBINE

This study examines the hydrodynamic characteristics of the Weis–Fogh-type water turbine by measuring the forces in the U and V directions on the wing (NACA0010 airfoil). The distance from the trailing edge of the wing to the wing shaft (rp), water channel width (h), and maximum opening angle (α) are important design factors that were selected as the experimental parameters. The maximum average efficiency and average power coefficient of this water turbine for a single wing were 40% and 0.6, respectively, at α = 40°, h = 1.5C, and U/V =2.0.

A Combined Series-Parallel Hybrid Envelope Amplifier for Envelope Tracking Mobile Terminal RF Power Amplifier Applications

An improved envelope amplifier architecture for envelope tracking RF power amplifiers is presented, consisting of two switching amplifiers and one linear amplifier. The first switching amplifier and the linear amplifier provide wideband and high-efficiency operation, while the second switching amplifier provides a reduced bandwidth variable supply to the linear amplifier to further reduce power loss. The first switching amplifier and the linear amplifier are fabricated together in a 150 nm CMOS process, while the second switching amplifier is external. Measurements show a maximum average efficiency of 82% for a 10 MHz LTE signal with a 6 dB PAPR at 29.7 dBm output power and an SFDR of 63 dBc for a single tone of 5 MHz driving an 8 Ω load.

Simultaneous silencing of endo‐β‐1,4 xylanase genes reveals their roles in the virulence of Magnaporthe oryzae

Due to functional redundancy, it is often difficult to genetically analyse the biological function of fungal cell wall-degrading enzymes that belong to a gene family. To overcome this difficulty, we used RNAi to knock-down (KD) multiple xylanase genes to elucidate their roles in the pathogenicity of the blast fungus, Magnaporthe oryzae. To obtain the maximum average efficiency of gene silencing for the xylanase genes, we used the 'building blocks method', in which a 40 bp sequence was chosen from an endoxylanase gene, and 10 such sequences from 10 endoxylanases were combined to make an artificial RNAi trigger by synthetic DNA. Quantitative RT-PCR analysis revealed that the transcript levels of all the expressed xylanase genes were significantly reduced in KD mutants with the artificial RNAi trigger. Even though the KD mutants did not completely lose their pathogenicity to host plants, the number of lesions, rate of penetration and extent of infected cells were all reduced in KD mutant-infected leaves. The degree of pathogenicity reduction was associated with the silencing levels of xylanase mRNA and enzymatic activity in the KD mutants. Cytological analysis indicated that xylanases play significant roles in both vertical penetration and horizontal expansion of M. oryzae in infected plants.

Optimization Design for Structural Parameters of Toroidal CVT for Automobiles

The optimization design model of structural parameters of toroidal continuously variable transmission (CVT) is established on the basis of analysis of its transmission ratios and contact parameters. The minimum cavity radium and the maximum average efficiency in the whole range of the transmission ratios are taken as objective functions, which oil film thickness and contact strength et al. are considered as constraint conditions. The evaluation function is established by using the multiplication-division method in the multi-objective optimization method, and structural parameters can be obtained by using Fmincon function in the Matlab software based on sequential quadratic programming(SQP) algorithm. The analysis results show that the cavity radius is reduced, the CVT becomes compacter, and the transmission efficiency is improved. This optimal design can improve the comprehensive capacity of this kind of CVT effectively.

Highly efficient extraction of a proton beam by using bent single crystals

A substantially increased beam extraction efficiency can be achieved in the case of a multiple beam’s passage through a crystal. This suggestion was verified in experiments with short (5–7 mm long) curved single crystal with bending angles of 1.5–1.7 mrad performed at the Institute of High Energy Physics. The peak effiency values obtained were 47±3%, and the maximum average efficiency was 42±2% for a 23% intensity taken from an accelerated beam. The maximum extracted beam intensity was 6×1011 protons per cycle.