Papers by Keyword: Operating Temperature

Abstract: Traditional silicon-based photodetectors are limited by the band gap of silicon, which results in a limited working wavelength range. In this report, due to the excellent properties of Indium Antimonide, the InSb/Si heterojunction photodetectors are fabricated. Under ambient temperature of 280K, as-prepared photodetectors show a specific detectivity of 9.310¹¹ cm Hz^1/2/W, responsivity of 54 mA/W, on/off ratio of 510⁴ under the laser irradiation of 635 nm. In order to explore the influence of working temperature on device performance, the photoresponse at different temperatures was tested. This report proved that as the working temperature increases, the responsivity and specific detectivity of the device decrease, and the performance of the device becomes worse.

Abstract: In order to optimized the power cable layout design in tunnel, and improved the operation ability of the cable line, this paper analyzed the cable rating and the short-circuit force under different arrangements. 220kV cable circuit was simulated in the tunnel with conditions of the flat and the trefoil arrangements. The temperature and the rating of the 220kV cable under the condition of the two arrangements were calculated in this paper. The short circuit force peak value and its direction of the cable line under short circuit current of 50kA under the condition of the two arrangements were simulated in this paper. The results show that, the cable rating in flat arrangement is better than in trefoil formation. The value and the direction of the short circuit force in tunnel are better in flat arrangement than in trefoil formation. So it is suggested that the flat arrangement is preferred when conditions permit.

Abstract: The impact of the thermal conductivity (k-value) change of polystyrene insulation material in building envelope due to changes in temperature on the thermal and energy performance of a typical residential building under hot climate is investigated. Indeed, the thermal and energy performance of buildings depends on the thermal characteristics of the building envelope, and particularly on the thermal resistance of the insulation material used. The thermal insulation material which is determined by its thermal conductivity, which describes the ability of heat to flow cross the material in presence of a gradient of temperature, is the main key to assess the performance of the thermal insulation material. When performing the energy analysis or calculating the cooling load for buildings, we use published values of thermal conductivity of insulation materials, which are normally evaluated at 24°C according to the ASTM standards. In reality, thermal insulation in building is exposed to significant and continuous temperature variations, due essentially to the change of outdoor air temperature and solar radiation. Many types of insulation materials are produced and used in Oman, but not enough information is available to evaluate their performance under the prevailing climatic condition. The main objective of this study is to investigate the relationship between the temperature and thermal conductivity of various densities of polystyrene, which is widely used as building insulation material in Oman. Moreover, the impact of thermal conductivity variation with temperature on the envelope-induced cooling load for a simple building model is discussed. This work will serve as a platform to investigate the effect of the operating temperature on thermal conductivity of other building material insulations, and leads to more accurate assessment of the thermal and energy performance of buildings in Oman.

Abstract: The concept of a UAV (unmanned aerial vehicle) with photovoltaic cells powered by a laser beam has been demonstrated as more firm, having higher usable power and more payloads than solar-powered ones, and features wide prospective. The theory models were based on the thermal equilibrium formulation which took into account of convective cooling raised by the flowing air and the radiation heat exchanges between the photovoltaic panel and the earth, and the atmosphere. Then, numerically, this paper investigated and analyzed the equilibrium temperature, energy efficiency, usable laser power density and maximum endurable laser power density of the photovoltaic panel, which can provide references for the choice of cooling methods and laser-power mission programming of the laser-powered UAVs.

Abstract: A method of solid-state recycling aluminum alloy using hot press forging process was studied as well as the possibility of the recycled chip to be used as secondary resources. This paper presents the results of recycled AA6061 aluminium alloy chip using different operating temperature for hot press forging process. Mechanical properties and microstructure of the recycled specimens and as-received (reference) specimen were investigated. The recycled specimens exhibit a good potential in the strength properties. The result for yield strength (YS) and ultimate tensile strength (UTS) at the minimum temperature 430°C is 25.8 MPa and 27.13 MPa. For the maximum operating temperature 520°C YS and UTS are 107.0MPa and 117.53 MPa. Analysis for different operating temperatures shows that the higher temperatures giving better result on mechanical properties and finer microstructure. The strength of recycled specimen increases due to the grain refinement strengthening whereas particle dispersion strengthening has minor effects. In this study, the recycled AA6061 chip shows the good potential in strengthening as the comparison of using only 17.5% of suggested pressure (70.0/400.0) MPa, the UTS exhibit 35.8% (117.58/327.69) MPa. This shows a remarkable potential of direct recycling by using hot press forging process.

Abstract: Effects of operating temperature on the fineness and yields of the ultrafine circulating fluid bed fly ashes (CFBAes) have been studied. Results show that the temperature of selection zone increased faster than that of crushing zone. Introduction of secondary air decreased the temperature of crushing zone, which would make the classifier invalid. Also, ambient temperature and insulation measures have a great impact on the ultrafine grinding in superheated steam jet mill

Abstract: The optimal performance of the solar-driven thermodynamics cycle system consisting of a solar collector and a four-temperature-level absorption refrigerator is investigated, based on the linear heat-loss model of a solar collector and the irreversible cycle model of a four-temperature-level absorption refrigerator. A fundamental optimum relation is derived, from which the optimum operating temperature of the solar collector, the maximum overall coefficient of performance and the corresponding coefficient of performance of the four-temperature-level refrigerator are determined. It is proven that the total thermal conductance of the heat exchangers must be divided optimally between the four heat exchangers. The effects of the cycle parameters on the optimum operating temperature of the solar collector and the performance of the system are discussed by detailed numerical examples. The results obtained can describe the optimal performance of solar-driven four-temperature-level refrigerator affected simultaneously by the internal and external irreversibilities.