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1.
Two subroutines have been developed which permit users of the TRNSYS programme to calculate the parameters of ambiental comfort (PMV and PPD).The first subroutine deals with the calculation of the view factors inside a room for all the values of the spatial coordinates and, thus, permits the average radiant temperature to be calculated in every position. The second subroutine has been developed in accordance with the indications of the ISO 7730 standard.Both subroutines have been validated and then interfaced to TRNSYS.The integrated programme has been utilised to compare the performances of different heating systems in terms of energy consumption and comfort, maintaining the temperature of the interior constant for different climatic conditions. 相似文献
2.
Two processes, namely shrinkage and primary fragmentation are known to be the major causes of size reduction of wood during its devolatilization in a fluidized bed combustor. A simple phenomenological model incorporating these effects to compute the average char size at the end of devolatilization is proposed. Experiments are conducted in a bubbling fluidized bed combustor using wood having three different shapes namely, cylinder, cuboid and sphere, to measure the average char size at the end of devolatilization. The model prediction of average char size agrees with the measured values within a deviation of 15%. An experimental correlation is derived to determine the number of fragments and is used to estimate the mean char size. 相似文献
3.
M. Sreekanth D. Ruben Sudhakar B.V.S.S.S. Prasad Ajit Kumar Kolar B. Leckner 《Fuel》2008,87(12):2698-2712
A two-dimensional model is developed for the determination of devolatilization time and char yield of cylindrical wood particles in a bubbling fluidized bed combustor. By using the concept of shape factor, the model is extended to particles of cuboid shape. The model prediction of the devolatilization time agrees with the measured data (present and those reported in the literature) for cylindrical and cuboidal shaped particles within ±20% while the char yield is predicted within ±17%. Influence of some important parameters namely, thermal diffusivity, external heat transfer coefficient and shrinkage, on the devolatilization time and char yield are studied. Thermal diffusivity shows noticeable influence on devolatilization time. The external heat transfer coefficient shows little influence beyond a value of 300 W/(m2 K). However particle shrinkage shows negligible effect on the devolatilization time but has a significant influence on the char yield. 相似文献
4.
5.
A three-phase three-switch buck-type pulsewidth modulation rectifier is designed for telecom applications in this paper. The rectifier features a constant 400-V output voltage and 5-kW output power at the three-phase 400-V mains. The principle of operation and the calculation of the relative on-times of the power transistors are described. Based on analytical relationships the stresses of the active and passive components are determined and the accuracy of the given calculations is verified by digital simulations. Exemplarily, a 5-kW power converter is then designed based on the analytical expressions and on switching loss measurements from a hardware prototype constructed with insulated gate bipolar transistor/diode power modules. The loss distribution of the components, the total efficiency, and the junction temperatures of the semiconductors are then evaluated in dependency on the operating point. Finally, the trade-off between the selected switching frequency and the admissible power range for the realized design is shown and a total efficiency of 95.0% is measured on the hardware prototype, where an excellent agreement with the theoretically evaluated efficiency is shown 相似文献
6.
The microstructure and properties of NdFeB sintered permanent magnets were analysed by different methods. Samples analysed were sintered and thermally treated. The hard magnetic Nd2Fe14B phase and amorphous neodymium-rich phase were observed by TEM. The neodymium-rich phase contained iron and boron, in elemental and in B2O3 form, which is known as a glass former. At the sintering temperature, Nd2Fe14B and the neodymium-rich phase are supersaturated with iron, which should be dissolved at the annealing temperature to react with neodymium and boron and form additional Nd2Fe14B phase. Iron precipitates of size up to 2 nm were detected in the Nd2Fe14B phase. These superparamagnetic precipitates of -Fe could affect the hard magnetic properties of NdFeB magnets. 相似文献
7.
8.
High T
c superconducting materials based on a PbO-modified Bi-Sr-Ca-Cu-O system with various ratios between the oxides were prepared by calcination at 800 °C and firing at 855 °C. From X-ray powder diffraction analysis data, the ratio of low- and high-temperature phases was calculated. The material with the nominal composition Bi2Pb0.5Sr2Ca2.5Cu3.5O
x
was chosen for further experimental work. Samples fired at 800 °C contain mostly the low-temperature phase (2212). Higher firing temperatures lead to the formation of the high T
c phase (2223) with T
c(R=0) over 100 K. Some samples were cold pressed and refired which increased the specific density to over 80% of the theoretical density. The composition of samples was investigated by X-ray powder diffraction analysis and by energy dispersive X-ray spectroscopy. The main phase in the material fired at 800 °C, is the low T
c phase 2212, and secondary phases are Ca2PbO4, unreacted CuO and traces of 2223 phase. At higher firing temperatures, the main phase is the high-temperature phase 2223. The material is still heterogeneous and contains Ca2PbO4. 相似文献
9.
Grain growth in donor doped BaTiO3 was studied below the temperature of liquid phase formation. It was found that a high donor concentration and high oxygen partial pressure effectively inhibit grain growth rate during sintering. Defect chemistry, derived from a model consistent with electrical measurements, well describes the grain growth properties of donor doped BaTiO3 in the subsolidus grain growth region. 相似文献
10.
Idilio Drago Rafael R. R. Barbosa Ramin Sadre Aiko Pras Jürgen Schönwälder 《Journal of Network and Systems Management》2011,19(2):298-304
Following the success of the First Workshop on the Usage of NetFlow/IPFIX (Pras et al. in J Netw Syst Manag 17(4), 2009) in 2008, the European EMANICS Network of Excellence organized a second workshop
in October 2009, held at Jacobs University Bremen. This report summarizes the workshop and presents its main conclusions. 相似文献