共查询到20条相似文献，搜索用时 8 毫秒
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PEGA HRNJAK 《传热工程》2013,34(3):61-62
Heat exchangers with microchannels (hydraulic diameter less than 1 mm) are attracting significant attention lately. Performance of these heat exchangers mostly evaporators is greatly affected by imperfect distribution of a two-phase fluid to each channel. This paper presents an overview of the issue, showing basic options to evenly distribute single and two-phase fluid and the methods to determine maldistribution. Special attention is given to describing two-phase regimes in an adiabatic horizontal header with R134a as a fluid, describing a two-phase map with area of good distribution. 相似文献
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Ibrahim Dincer 《国际能源研究杂志》1995,19(9):791-801
This paper presents the new, simple but powerful effective Nusselt–Reynolds correlations for estimating the effective convective heat transfer coefficients of spherical and cylindrical products cooled in water and air flows. In this respect, both experimental and theoretical works were obtained. In the experimental case, several spherical and cylindrical products, namely, tomatoes, pears and cucumbers were cooled in water and air flow and their centre temperature variations were measured. In the theoretical case, the effective convective heat transfer coefficients for the individual spherical and cylindrical products were determined using the centre temperature data in the present approach including Dincer's models. Therefore, the new Nusselt–Reynolds correlations were developed using the effective convective heat transfer coefficient values and a general diagram of Nu/Pr1/3 against Reynolds number was drawn. This study indicates that the present effective Nu–Re correlations are capable of estimating the effective convective heat transfer coefficients of any spherical and cylindrical shaped products exposed to water and air cooling in practical applications in a simple and accurate manner. 相似文献
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V.K.V.P. Srirapu M. Kumar R. Awasthi R.N. Singh A.S.K. Sinha 《International Journal of Hydrogen Energy》2013
Pure and Fe-substituted manganese molybdates with nominal compositional formula FexMn1−xMoO4 (x = 0, 0.25, 0.50 and 0.75) have been prepared by a co-precipitation method at pH ≈ 2 and characterized by FT-IR, XRD, XPS, TEM, electrochemical impedance and polarization techniques. The oxygen evolution reaction (OER) study reveals that Fe substitutions from 0.25 to 0.75 mol for Mn increase the apparent electrocatalytic activity of the base oxide showing maximum with 0.5 mol Fe. At E = 0.60 V vs. Hg/HgO in 1 M KOH at 298 K, the apparent activity of the base oxide increased ∼58 times. It is observed that on Fe addition, the Tafel slope decreases from ∼60 to ∼35 mV, however, the order of the OER with respect to OH− concentration as observed ∼2 on the base oxide (i.e. MnMoO4) does not change. 相似文献
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Unbundling electric generation and transmission services 总被引：1，自引：0，他引：1
Today's typical vertically integrated utility sells electricity and associated services as a bundled product. These ancillary services support and make possible the provision of the basic services of generating capacity, energy supply, and power delivery. These ancillary services include the following: management of generating units; reserve generating capacity to follow variations in customer loads, to provide capacity and energy when generating units or transmission lines suddenly fail, to maintain electric-system stability, and to provide local area security; transmission-system monitoring and control; replacement of real power and energy losses; reactive-power management and voltage regulation; transmission reserves; repair and maintenance of the transmission network; metering, billing, and communications; and assurance of appropriate levels of power quality. 相似文献
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