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A 117.8 l three-dimensional pressure vessel is used to study the methane hydrate dissociation with the steam assisted gravity drainage (sagd) method. it is called the pilot-scale hydrate simulator (phs). this study proposes the evaluation and the comparisons of the gas production performance by sagd method from the methane hydrate reservoir with different steam injection rates. it indicates that the experiment could be divided into three main stages: the original gas releasing stage, the original and the hydrate-originating gas releasing stage, and the hydrate-originating gas releasing stage (the sagd process). furthermore, the temperature change consists of the four periods: decreasing dramatically, keeping stable, rising gradually, and keeping steady. with the injected steam flowing downwards and sideways, the steam chamber is expanding. the gas production rate increases with the steam injection rate, while the energy efficiency ratio (eer) and gas-to-water ratios are improved by the decrease of the steam injection rate. (c) 2013 elsevier ltd. all rights reserved.

Abstract Spark-ignition (SI) aviation piston engines are widely used on light helicopters and unmanned aerial vehicles (UAVs) because of the high-power density and ultra-high cost performance. Kerosene with high flash point is expected to improve safety of aforementioned aircrafts by replacing gasoline. However, in spark-ignition mode, kerosene is difficult to mix and is easy to knock. Short-chain alcohols have high volatility and octane number which can just make up for some defects of kerosene. In this paper, three kinds of alcohols including ethanol, n-propanol and n-butanol were blended with aviation kerosene (RP-3) by volume fraction of 30%, 50%, 70%, respectively. The combustion and emission characteristics of the blended fuels were deeply studied on a typical spark-ignition aviation piston engine. Meanwhile, engine performance fueled with commercial gasoline was also tested for comparison. Results indicated that alcohol/kerosene blends could reach higher brake thermal efficiency (BTE) (alcohol ratio ≥50%) compared to gasoline. Carbon monoxide (CO) and nitrogen oxides (NOx) emissions of blended fuels expressed dramatically descending. With the increase in alcohol ratio, the CO, hydrocarbons (HC) and soot emissions gradually decreased. The brake thermal efficiency showed an upward trend with the increase of alcohol ratios. The brake thermal efficiency of E70, P70 and B70 were increased by 2.15%, 3.52% and 6.51%, and the CO emissions of E70, P70 and B70 were reduced by 39.8%, 38.5% and 49.0%, respectively, compared to those of gasoline. Notably, n-butanol/kerosene blends exhibited the better combustion and emission characteristics, which had the higher efficiency and lower CO, HC and soot emissions.

Abstract This paper presents a parametric analysis for a medium to large size (290–500 MW th receiver thermal power) central receiver plant considering the present market trends. The analysis is divided in 4 steps: • Size and location analysis: for a medium to large size central receiver power plant, three turbine power and three different locations that are involved in the development of power tower plants, have been analyzed to assess the impact over the design characteristics of the solar field and receiver sub-systems and over the levelized electricity cost. • Technology analysis: as commercial power tower plants in operation today are mainly using steam and molten nitrate salts, the present analysis compares the two main technologies, without thermal energy storage to evaluate both under similar design conditions. • Storage analysis: thermal energy storage increases the value of electricity produced and the plant capacity factor for both technologies (steam and molten nitrate salts). For this reason, the analysis shows for each optimized solar field and receiver thermal power, the optimum combination of turbine power and thermal energy storage that minimizes the levelized electricity cost, for both technologies. • Component’s cost analysis: market trends are focused on the specific cost reduction by means of larger plant size and through an improved economy of scale. As a result, and based on baseline cost parameters widely accepted in solar industry, an analysis over the specific costs of major components on the electricity cost has been carried out, to lead where the research and development efforts should be made.

The coupling between unsteady heat release and acoustic perturbations can lead to self-sustained thermoacoustic oscillations, also known as combustion instability. When such combustion instability occurs, the pressure oscillations may become so intense that they can cause engine structural damage and costly mission failure. Thus there is a need to understand the coupling physics between acoustic waves and unsteady combustion and to identify a measure to quantify the interaction between the flame and acoustics. The present work studies linear and nonlinear response of a conical premixed laminar flame to oncoming acoustic disturbances. Unsteady heat release from the flame is assumed to be caused by its surface area variations, which results from the fluctuations of the oncoming flow velocity. The classical G-equation is used to track the flame front variation in real-time. Second-order finite difference method is then used to expand the flame model. Time evolution of the flame surface distortions is successfully captured. To quantify the dynamic response of the flame to the acoustic disturbances, system identification is then conducted to estimate the linear and nonlinear flame transfer function. Good agreement is obtained. Finally, transfer function of an actuated open–open thermoacoustic system is experimentally measured by injecting a broad-band white noise. The present work opens up new applicable way to measure heat-driven acoustics transfer function in a thermoacoustic system by simply implementing white noise.

Abstract The rapid development of power electronic devices has made them have higher power density, which puts forward higher requirements for cooling technology. The contribution of this paper is the integrated design of the liquid cooled heat sink for a 30 kW motor inverter considering the distribution of power devices. In order to find an optimal heat sink configuration, the cooling performance of three different configurations of heat sinks was investigated. And the distribution characteristics of the temperature and fluid velocity field were compared and analyzed. The heat sink with serpentine channel configuration was selected due to its best temperature uniformity and cooling characteristic. In addition, the effects of geometric parameters (fin thickness) and flow parameters (flow rate) on cooling performance were further studied. On this basis, the geometrical configuration of the heat sink was optimized. The experimental results of the optimized heat sink are in good agreement with the numerical simulation results. The motor inverter achieves high power density of 9.677 kW/kg.

(c) 2013 Elsevier Ltd. All rights reserved. This is the authors' accepted and refereed manuscript to the article, post-print. Released with a Creative Commons Attribution Non-Commercial No Derivatives License.

Abstract We have derived an analytic model describing the interior temperature difference as a function of the load current of a thermoelectric generator (TEG); we have also proposed a method to extract the intrinsic and extrinsic Seebeck coefficients and resistances of TEG using experimental current–voltage curves. The decrement of internal temperature difference is almost linearly depending on load current of the TEG. From the experimental results, using a thermoelectric (TE) module with a thermal conductance of 3.52 W/K and a parasitic thermal conductance of 50 W/K, the effective internal electrical resistance was increased by approximately 5%, but the effective Seebeck coefficient was attenuated by approximately 13%, as compared to the intrinsic parameters. The relationship between the output power reduction factor and limited thermal conductance of TEG packaging was also derived. Approximately 25% of the maximum output power is lost because of the parasitic thermal resistance of the TE module used in the experiment.

Abstract Wind power technology is one of the cleanest electricity generation technologies that are expected to have a substantial share in the future electricity mix. Nonetheless, the expected increase in the market share of wind technology has led to an increasing concern of the availability, production capacity and geographical concentration of the metals required for the technology, especially the rear earth elements (REE) neodymium (Nd) and the far less abundant dysprosium (Dy), and the impacts associated with their production. Moreover, Nd and Dy are coproduced with other rare earth metals mainly from iron, titanium, zirconium, and thorium deposits. Consequently, an increase in the demand for Nd and Dy in wind power technology and in their traditional applications may lead to an increase in the production of the host metals and other companion REE, with possible implications on their supply and demand. In this regard, we have used a dynamic material flow and stock model to study the impacts of the increasing demand for Nd and Dy on the supply and demand of the host metals and other companion REE. In one scenario, when the supply of Dy is covered by all current and expected producing deposits, the increase in the demand for Dy leads to an oversupply of 255 Gg of total REE and an oversupply of the coproduced REE Nd, La, Ce and Y. In the second and third scenarios, however, when the supply of Dy is covered by critical REE rich deposits or Dy rich deposits, the increase in Dy demand results in an oversupply of Ce and Y only, while the demand for Nd and La exceeds their supply. In the case of an oversupply of REEs, the environmental impacts associated with the REEs production should be allocated to Dy and consequently to the technologies that utilize the metal. The results also show that very large quantities of thorium will be co-produced as a result of the demand for Dy. The thorium would need to be carefully disposed of, or significant thorium applications would need to be found.

We demonstrate that a novel device design, where a shape-engineered tilted-leg thermopile structure is employed, significantly enhances the output voltage in the transverse direction. Owing to the shape engineering of the leg geometry, an additional temperature gradient develops along the long direction of the leg, which is perpendicular to the direction of the applied temperature gradient, thereby generating an additional Seebeck voltage V_SE that adds to the Anomalous Nernst effect (ANE) voltage V_ANE. We further show that a simple adjustment of electrode position within the device can further increase V_SE. The tilted leg device with electrode adjustment demonstrates a 990% enhanced transverse output voltage compared to that of conventional rectangular leg thermopile-structured devices, wherein only the ANE occurs. This combined output voltage from both the Seebeck effect and ANE is equivalent to the value that surpasses the state-of-the-art ANE materials and devices currently available. The numerical analysis shows the tendencies of the electrical and thermal outputs of the tilted-leg device, which guides a way to further improve the output voltage. Our study paves the way to develop highly efficient transverse TE devices that can overcome intrinsic materials challenges by utilizing the degree of freedom of device design.