Maximum Net Output Research Articles

Impact of built-in and actual expansion ratio difference of expander on ORC system performance

Built-in expansion ratio is set with screw expander design, influenced by the geometric shape, size, and flow characteristic. Actual expansion ratio, which equals to the evaporation pressure divided by the back pressure of discharge line, is determined by operating conditions. In the previous ORC system studies, the efficiency of expander is usually assumed as constant. However, the built-in and actual expansion ratio difference affects the screw expander efficiency greatly in a practical application. Therefore, a correction factor is needed for characterization. The purpose of this paper is to study the impact on ORC system performance caused by the expansion ratio difference. Six working fluids (R123, R245fa, n-Pentane, Isopentane, n-Hexane and Cyclohexane) have been selected as the candidates and system net output and thermal efficiency have been chosen to evaluate the system performance. The test system is defined as a kilowatt class since the net output is about 1 kW. In the whole simulation, the heat source condition remains unchanged, the condensation temperature maintains 303.2 K and the evaporation temperature ranges from 333.2 to 393.2 K. The results show that the correction factor decreases faster in the under-expansion condition than it does in the over-expansion condition. Furthermore, the actual expansion ratio which results in the maximum net output is not equal to, but higher than the built-in one. After correction, all the optimal evaporation temperature, maximal net output and thermal efficiency have been reduced, as is meaningful in the system determination.

Relationship between net electric power and radial build of DEMO based on ITER steady-state scenario parameters

Relations between a net electrical output power and dimensions of components in radial build are investigated based on the ITER plasma performance to develop a conceptual design of DEMO with the net electrical output power of several hundred MW. Reducing the dimensions of in-vessel components and increasing the thickness of the toroidal field coil contribute to strengthen the toroidal magnetic field at plasma, which brings about increase in a net electrical output power. The relation between the minimum plasma major radius and the maximum net electrical output power is clarified. Furthermore effects of improvements in the ITER plasma performance on the net electricity are also analyzed; indicating the increase of normalized beta could have advantage from the viewpoint of the divertor heat load because the increase of synchrotron radiation loss power contributes to reduce the divertor heat load, though the higher energy confinement is required.

Parametric and working fluid analysis of a dual-loop organic Rankine cycle (DORC) used in engine waste heat recovery

A novel dual-loop organic Rankine cycle (DORC) is proposed in this study, which consists a high-temperature (HT) loop and a low-temperature (LT) loop to recover the waste heat of the exhaust, engine coolant and residual heat of the HT loop. Net output power, utilization rate of engine coolant, DORC thermal efficiency and exergy efficiency are chosen as the objective functions. R124, R134a, R245fa, R600, R600a and R1234yf are chosen as the candidate working fluids of the LT loop. Based on engine data and pre-set model parameters, energy and exergy analysis are conducted. Results show that maximum net output power, utilization rate of the engine coolant and exergy efficiency are obtained with R1234yf at Tevp,HT=570K and Tevp,LT=343K and corresponding values are 36.77kW, 96.8% and 55.05%. The top two ηth are obtained with R600 and R245fa at Tevp,HT=570K and Tevp,LT=365K and corresponding values are 20.07% and 20.06%. Furthermore, based on the R1234yf-based system operating at Tevp,HT=570K and Tevp,LT=343K, the maximum irreversibility occurs in turbine and exergy efficiency of evaporator E3,LT is worst, which are the optimization objectives for the improvement of system exergy performance. In addition, based on Pnet, ηth and ηe, for all working fluids, system performs better at high operating load. R1234yf is found to be a better working fluid for high operating load. R124 possesses the worst performance under all operating loads.

IMPROVING PRODUCTIVITY, WATER AND ENERGY USE EFFICIENCY IN LOWLAND RICE (ORYZA SATIVA) THROUGH APPROPRIATE ESTABLISHMENT METHODS AND NUTRIENT MANAGEMENT PRACTICES IN THE MID-ALTITUDE OF NORTH-EAST INDIA

SUMMARYRice is the major staple food crop in the North Eastern Region of India (26.2 million hectare geographical area) and the region has a deficit of 1.40 million tones of rice, mainly due to low productivity (1.72 t ha−1). Field experiments were conducted for the first time to evaluate the new techniques of rice cultivation, viz. the system of rice intensification (SRI) and integrated crop management (ICM) along with conventional rice culture (CRC) for improving productivity, water and energy use efficiency during the rainy seasons of 2004–07 at the ICAR Research Complex for North Eastern Hill Region, Umiam, Meghalaya (950 m msl), India. Three stand establishment methods, viz. SRI, ICM and CRC in main plots, and five nutrient management practices, viz. recommended dose of fertilizers (RDF = 80:26:33 kg NPK ha−1), farmyard manure (FYM) 10 t ha−1, RDF + FYM 5 t ha−1, 50% RDF + FYM 10 t ha−1, and a control (no fertilizer and manure) in sub-plots, were tested in a split-plot design; only few meaningful interactions were found. Results showed a higher number of panicles per square metre under CRC and ICM compared with SRI. However, the number of panicles per hill, grains per panicle and the test weight remained higher in the SRI method. In terms of mean grain yield, ICM (4.86 t ha−1) and SRI (4.72 t ha) produced 12.8 and 9.6%, respectively, higher grain yield over CRC (4.3 t ha−1). Among the nutrient management practices, the application of RDF + FYM 5 t ha−1(5.0 t ha−1) and 50% RDF + FYM 10 t ha−1(4.87 t ha−1) not only produced higher grain yield of rice (23.8 and 20.5%, respectively, higher yield over control) but also maintained higher soil available N, P and organic carbon at harvest compared with other nutrient management practices. Photosynthesis rate and water use efficiency were found to be significantly (p< 0.05) higher under SRI, whereas the transpiration rate was higher under CRC. The ICM method recorded maximum net return and energy output to input ratio, which was followed by SRI and CRC. Therefore, the ICM method of rice cultivation would be the preferred option for the sub-tropical mid-hills of eastern Indian Himalayas.

Analysis of regenerative dual-loop organic Rankine cycles (DORCs) used in engine waste heat recovery

In this paper, three regenerative dual-loop organic Rankine cycle (DORC) systems are proposed to compare with the simple DORC system. Waste heat of the exhaust, engine coolant and residual heat of the HT loop are recovered in these four systems. In the HT loop, water and siloxane are chosen as working fluid candidates, transcritical cycle and subcritical cycle are evaluated. In the LT loop, R143a is used as the working fluid and transcritical cycle is adopted. Net output power and exergy efficiency are selected as objective functions. Based on the engine data and mathematic model, operating parameters are optimized and component irreversibility is analyzed. Results show that low condensation temperature of the HT loop is beneficial to performance optimization. The inlet temperature of turbine THT should be high for wet fluids in subcritical cycle and low for dry fluids in both subcritical and transcritical cycles. Maximum net output power and exergy efficiency are obtained when water is used as the working fluid of the HT loop and no regenerator is adopted in the system. Corresponding values are 39.67kW and 42.98%. When siloxane is used as the working fluid of the HT loop, DORC with double regenerators performs better. For all systems evaluated, irreversibilities of condenser CLT and turbine TLT are large.

Thermodynamic analysis of a dual loop heat recovery system with trilateral cycle applied to exhaust gases of internal combustion engine for propulsion of the 6800 TEU container ship

A dual loop waste heat recovery power generation system that comprises an upper trilateral cycle and a lower organic Rankine cycle, in which discharged exhaust gas heat is recovered and re-used for propulsion power, was theoretically applied to an internal combustion engine for propulsion in a 6800 TEU container ship. The thermodynamic properties of this exhaust gas heat recovery system, which vary depending on the boundary temperature between the upper and lower cycles, were also investigated. The results confirmed that this dual loop exhaust gas heat recovery power generation system exhibited a maximum net output of 2069.8 kW, and a maximum system efficiency of 10.93% according to the first law of thermodynamics and a maximum system exergy efficiency of 58.77% according to the second law of thermodynamics. In this case, the energy and exergy efficiencies of the dual loop system were larger than those of the single loop trilateral cycle. Further, in the upper trilateral cycle, the volumetric expansion ratio of the turbine could be considerably reduced to an adequate level to be employed in the practical system. When this dual loop exhaust gas heat recovery power generation system was applied to the main engine of the container ship, which was actually in operation, a 2.824% improvement in propulsion efficiency was confirmed in comparison to the case of a base engine. This improvement in propulsion efficiency resulted in about 6.06% reduction in the specific fuel oil consumption and specific CO2 emissions of the main engine during actual operation.

Water‐Saving Crop Planning Using Multiple Objective Chaos Particle Swarm Optimization for Sustainable Agricultural and Soil Resources Development

AbstractEstablishing a water‐saving planting structure is necessary for the arid, water‐deficient regions of northern China and of the world. Optimizing and adjusting a water‐saving agricultural planting structure is a typical semi‐structured, multi‐level, multi‐objective group decision‐making problem. Therefore, optimization can be best achieved with a swarm intelligence algorithm. We build an optimization model for a water‐saving planting structure with four target functions: (1) maximum total net output, (2) total grain yield, (3) ecological benefits, and (4) water productivity. The decision variable is the yearly seeded area of different crops, and its restrictions are the farmland area, the agricultural water resources, and the needs of the people and other farming‐related industries. Multiple objective particle swarm optimization (MOPSO) is an efficient optimization method, but its main shortcoming is that it can easily fall into a local optimum. Multiple objective chaos particle swarm optimization (MOCPSO) will greatly improve the searching performance of the algorithm by placing chaos technology with the advantages of ergodicity into MOPSO. When MOCPSO is used to solve the multi‐objective optimization model in the middle portion of the Heihe River basin, the results show that MOCPSO has the advantages of a high convergence speed and a tendency not to fall easily into a local optimum. After adopting a water‐saving agricultural planting structure, irrigation water would be reduced by about 7%, which would provide tangible economic, social, and ecological benefits for sustainable agricultural development.

Vertical coupling between gap plasmon waveguides

This work examines vertical coupling between gap plasmon waveguides for use in high confinement power transfer and power splitting applications at 1.55 microm free space wavelength. The supermode interference method is used to obtain key coupler performance parameters such as coupling length, extinction ratio, net coupled output power, radiated power, and reflected power as a function of waveguide center-to-center spacing, core refractive index, and gap width. The initial power distribution among the two coupler supermodes is obtained via the mode matching method for a single input waveguide feed. Excellent agreement with three-dimensional finite difference time domain simulations is observed for the case of square 50 nm gaps with core refractive indices of 2.50 and a center-to-center spacing of 112 nm. Local maxima in the net coupled output power are found to coincide with local minima in the coupling length. An increase in the core refractive index from 1.00 to 2.5 increases the local maximum net coupled output power from 6.4% to 49% but decreases the extinction ratio from 12.7 to 6.94. A sweep of the width of the core from 25 to 100 nm increases the net coupled output power from 43.7% to 52.0%, but increases the coupling length from 1.58 to 3.19 ???m and decreases the extinction ratio from 7.39 to 6.57.

Scaling of maximum net force output by motors used for locomotion

Biological and engineered motors are surprisingly similar in their adherence to two or possibly three fundamental regimes for the mass scaling of maximum force output (Fmax). One scaling regime (Group 1: myosin, kinesin, dynein and RNA polymerase molecules; muscle cells; whole muscles; winches; linear actuators) comprises motors that create slow translational motion with force outputs limited by the axial stress capacity of the motor, which results in Fmax scaling as motor mass0.67 (M0.67). Another scaling regime (Group 2: flying birds, bats and insects; swimming fish; running animals; piston engines; electric motors; jets) comprises motors that cycle rapidly, with significant internal and external accelerations, and for whom inertia and fatigue life appear to be important constraints. The scaling of inertial loads and fatigue life both appear to enforce Fmax scaling as M1.0 in these motors. Despite great differences in materials and mechanisms, the mass specific Fmax of Group 2 motors clusters tightly around a mean of 57 N kg(-1), a region of specific force loading where there appears to be a common transition from high- to low-cycle fatigue. For motors subject to multi-axial stresses, the steepness of the load-life curve in the neighborhood of 50-100 N kg(-1) may overwhelm other material and mechanistic factors, thereby homogenizing the mass specific Fmax of grossly dissimilar animals and machines. Rockets scale with Group 1 motors but for different mechanistic reasons; they are free from fatigue constraints and their thrust is determined by mass flow rates that depend on cross sectional area of the exit nozzle. There is possibly a third scaling regime of Fmax for small motors (bacterial and spermatazoan flagella; a protozoan spring) where viscosity dominates over inertia. Data for force output of viscous regime motors are scarce, but the few data available suggest a gradually increasing scaling slope that converges with the Group 2 scaling relationship at a Reynolds number of about 10(2). The Group 1 and Group 2 scaling relationships intersect at a motor mass of 4400 kg, which restricts the force output and design of Group 2 motors greater than this mass. Above 4400 kg, all motors are limited by stress and have Fmax that scales as M0.67; this results in a gradual decline in mass specific Fmax at motor mass greater than 4400 kg. Because of declining mass specific Fmax, there is little or no potential for biological or engineered motors or rockets larger than those already in use.

Maximum output of an OTEC power plant

This paper theoretically investigates the effects of the temperature and flowrate of cold seawater on the net output of an OTEC plant. Parameters of pipe length, pipe diameter, seawater depth, and the flowrate of seawater are considered. It shows that a maximum output of the net work exists at a certain flowrate of cooling seawater. The output work is higher for a larger ratio of warm to cold seawater flow rate. For a lower cold seawater temperature, the maximum net output and the corresponding required flow rate of cold seawater becomes larger. The pipe diameters corresponding to maximum net output increase with decreasing cold seawater temperature for fixed flow velocity in pipes. In addition, a larger maximum net output can be obtained by employing a higher temperature of the surface warm seawater.

Rates of nitrogen application required to achieve maximum energy efficiency for various crops: results of a long-term experiment

A long-term experiment with four rates of mineral nitrogen (N) application (averaged across all the crops in a crop rotation: 0, 50, 100, 150 kg ha −1 per year) was conducted on a fertile loess-derived soil in central Germany. The objectives of this study were to (i) determine the rates of mineral nitrogen N application required for maximum net energy output (energy output minus energy input), maximum energy output/input ratio, and minimum energy intensity (energy input per unit grain equivalent) for various crops in a realistic crop rotation (potatoes [ Solanum tuberosum L.], winter wheat [ Triticum aestivum L.], winter barley [ Hordeum vulgare L.], sugar beets [ Beta vulgaris L.], spring barley [ Hordeum vulgare L.]): (ii) identify long-term trends (from 1968 to 2000) in the rates of mineral N application necessary to achieve the most efficient use of energy in the production of winter wheat and (iii) assess the effects of changing the system boundaries and the energy equivalents assigned to selected inputs on the energy balance by means of a sensitivity analysis. In the last two crop rotations (1989–1993 and 1994–1999), the amount of N fertilizer required to maximize net energy output of the main products (cereal grains, beet roots) increased in the order sugar beets–winter wheat–winter barley. At optimum N fertilization, the net energy output increased in the order winter barley–winter wheat–sugar beets. Averaged across the two rotations, the N fertilizer demand for a maximum output/input ratio and minimum energy intensity increased in the order sugar beets–winter wheat–winter barley. There was no clear-cut time trend in the rate of N application required to maximize grain yield and net energy output of wheat; maximum grain yield, maximum net energy output, and output/input ratio increased significantly with time, whereas the minimum energy intensity decreased over the experimental period. For all the crops, the rate of N application required for the maximum net energy output was much higher than that required for the maximum output/input ratio and minimum energy intensity.

２，２，３，３，３‐ペンタフルオロ‐１‐プロパノールの動作流体への応用

Thermodynamic properties and thermal stability of working fluids used in Rankine cycle systems and heat pumps were studied.Five fluids, R 114, 2, 2, 2-triflu oroethanol, 2, 2, 3, 3-tetrafluoro-1-propanol, 2, 2, 3, 3, 3-pentafluoro1-propanol and azeotropic mixture of the pentafluoro-l-propanol with water were chosen as working fluids and their thermodynamic proparties and cyclic properties were investigated at 140∼200°C.The results showed that pentafluoro-l-propanol could exibit the maximum gross and net output above 180°C with neither possible inflammability nor deterionaion of thermal stability.

Energy analysis of wave and tidal power

Energy requirements for building wave and tidal-power systems have been estimated. For wave-power systems, the relationship between energy requirements and extraction efficiency is examined. It is found that a point of maximum net output is reached, beyond which further increases in extraction efficiency result in decreased net energy. Energy analysis thus identifies a limit on the energy which could, in principle, be extracted by a wave-energy system. Although similar limits could be identified for other types of energy source, the tidal-power analysis is confined to a brief comparison of energy inputs and outputs.

Numerical analysis of a combustion-driven gasdynamic laser

A theoretical analysis and partial optimization of an open-cycle CO/sub 2/ cw-GDL (gasdynamic laser) using benzene C/sub 6/H/sub 6/ and kerosene C/sub 12/H/sub 24/ combustion with air is presented. The calculations are performed for an equivalency air/fuel ratio equal to 1 and the stagnation pressure p/sub 0/ equal to 15 atm, with geometrics dimensions of the lasers being optimized for maximum net output radiation power per unit mass flow. In both cases, the possibility of constructing a high-power cw-GDL supplied with these fuels is suggested. For combustion of C/sub 6/H/sub 6/ a specific energy P/sub g/ = 11 kW/kg-sec/sup -1/; whereas for the calculated ideal CO/sub 2/-N/sub 2/-H/sub 2/O mixture (containing 12 percent CO/sub 2/ and 0.9 percent H/sub 2/O), P/sub g/ = 18 kW/kg-sec/sup 1/. The influence on laser performance of stagnation pressure, stagnation temperature, expansion ratio, and air/fuel ratio has been examined partially.

The Duality of Technology and Economic Behaviour

The usual starting-point of the modern theory of production is the set of production possibilities, consisting of all production plans available to the producing unit.3 Given the properties of the set of feasible production plans, the production function and profit function can be derived and characterized. For any feasible plan the production function gives the maximum net output of any commodity as a function of the net outputs of all other commodities. The profit function gives the maximum value of profit for any feasible production plan as a function of the prices of all commodities. The theory of marginal productivity provides a characterization of the set of production possibilities from the technological point of view. Our first objective is to present a modern approach to the theory of marginal productivity, employing the production function and the marginal productivity correspondence. The marginal productivity correspondence may be identified with the gradient of the production function, wherever the gradient exists. Otherwise, the marginal productivity correspondence takes a set of possible values rather than a single value. Our second objective is to present equivalent specifications of the set of production possibilities, the production function and the marginal productivity correspondence. We take a characterization of any one of the three as a starting-point of the theory of production and derive properties of the other two. We characterize the production function in terms of the properties of the marginal productivity correspondence. We also derive properties of the set of production possibilities from properties of the production function, reversing the line of reasoning that has become conventional in the theory of production. Our third objective is to characterize the set of feasible production plans from the point of view of economic behaviour. For this purpose we present a theory of supply that parallels the theory of marginal productivity. We develop equivalent specifications of the profit function, the supply correspondence, and the set of price and profit possibilities. Any one of the three can be taken as a starting point for the theory of supply. Our final objective is to link the theory of supply with the theory of marginal productivity and to demonstrate the equivalence of the technological and behavioural view-