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  • Articles  (819)
  • Springer  (819)
  • American Chemical Society (ACS)
  • American Geophysical Union
  • American Meteorological Society
  • National Academy of Sciences
  • 2015-2019  (775)
  • 2005-2009
  • 1980-1984  (44)
  • 2019  (360)
  • 2017  (415)
  • 1982  (44)
  • Heat and Mass Transfer  (229)
  • 888
  • Physics  (819)
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  • Articles  (819)
Publisher
  • Springer  (819)
  • American Chemical Society (ACS)
  • American Geophysical Union
  • American Meteorological Society
  • National Academy of Sciences
Years
  • 2015-2019  (775)
  • 2005-2009
  • 1980-1984  (44)
Year
  • 11
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉In this work, an experimental study has been carried out to analyse the effect of wavy delta winglets on Nusselt number (〈em〉Nu〈/em〉) and friction factor (〈em〉f〈/em〉) in solar air passage for a specified range of system and operating parameters. The geometrical parameters considered are the number of waves (〈em〉ϕ〈/em〉)=3 to 7, the relative longitudinal pitch (〈em〉P〈/em〉/〈em〉H〈/em〉)=3 to 6, and the angle of attack (〈em〉α〈/em〉) = 30° to 75°. A fixed values of relative winglet chord length (〈em〉c/H〈/em〉 = 1.4) and relative blockage height (b/H = 0.5) are considered in the present study. The experimental data are generated for Nusselt number and friction factor for different combinations of geometrical and flow parameters and correlations for 〈em〉Nusselt number〈/em〉 and friction factor are also developed. Further, the developed correlations are deployed for the parametric optimization based on effective efficiency.〈/p〉
    Print ISSN: 0947-7411
    Electronic ISSN: 1432-1181
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 12
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The effects of various factors of the pulsed electric field (PEF) as an apple osmotic dehydration (OD) preprocess by using response surface methodology (RSM) are investigated and optimized in this paper. Electric field strength, pulse numbers and pulse duration were considered as PEF pretreatment effective factors in constant osmotic dehydration conditions such as concentration and temperature. After 4 h of osmosis, the results indicate decrease in amounts of water loss (WL) and solid gain (SG) by increasing field strength from 1 to 2 kV/cm and decreasing pulse duration from 0.5 to 0.02 s, respectively. The effect of increasing the pulse numbers from 8 to 16 give rise to the increase in amounts of water loss and solid gain at first and then by increasing to 24 pulses, the decrease in these amount has been evident. The ratio of water loss to solid gain (WL/SG) and response surface methodology (RSM) were used for optimization effects of PEF factors on the OD process. In optimal values of electric field strength, pulse numbers and pulse duration, the WL/SG ratio provided highest reduction sample mass.〈/p〉
    Print ISSN: 0947-7411
    Electronic ISSN: 1432-1181
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 13
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉In the present work, the heat transfer through a solar thermal collector (STC) provided with jet air impingement on the absorbent plate fitted with multi V-shaped protrusion ribs is investigated experimentally. The investigation is carried out for geometric parameters such as Relative width ratio (〈em〉W〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉/〈em〉W〈/em〉〈sub〉〈em〉APR〈/em〉〈/sub〉), Relative protrusion rib height (〈em〉h〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉/〈em〉d〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉), Relative pitch ratio (〈em〉P〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉/〈em〉h〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉), Angle of attack (〈em〉α〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉) respectively. The values of the streamwise pitch ratio (〈em〉X〈/em〉〈sub〉〈em〉SW〈/em〉〈/sub〉/〈em〉d〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉) = 0.40, spanwise pitch ratio (〈em〉Y〈/em〉〈sub〉〈em〉SW〈/em〉〈/sub〉/〈em〉d〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉) = 0.85 and jet diameter ratio (〈em〉d〈/em〉〈sub〉〈em〉j〈/em〉〈/sub〉/〈em〉d〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉) = 0.064 are kept constant. The overall performance of STC is effectively evaluated by varying Reynolds number (〈em〉Re〈/em〉) in the range 2500–35,000. The results obtained from the experiments shows that the impingement jets flow on multi V-shaped protrusion ribs absorber plate accelerated the heat transfer through the solar collector channel. The optimal augmentation is obtained at 〈em〉W〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉/〈em〉W〈/em〉〈sub〉〈em〉APR〈/em〉〈/sub〉= 5, 〈em〉h〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉/〈em〉d〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉= 0.9, 〈em〉P〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉/〈em〉h〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉 = 8 and 〈em〉α〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉 = 65° respectively. Thermal-hydraulic performance parameter ( 〈em〉η〈/em〉〈sub〉〈em〉PR〈/em〉〈/sub〉) has also been investigated and the maximum value of 3.44 is obtained for the range of parameters studied.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 14
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉In this manuscript, the heat transfer coefficient of de-ionized water based nanofluid’s containing 〈em〉Al〈/em〉〈sub〉〈em〉2〈/em〉〈/sub〉〈em〉O〈/em〉〈sub〉〈em〉3〈/em〉〈/sub〉 nanoparticles under natural convection is experimentally investigated. The thermophysical properties of the prepared nanofluid samples which have great roles in the heat transfer process such as the thermal conductivity and viscosity are experimentally measured and their effects are discussed. Furthermore, the transient temperature of the hot and cold walls and the other sides of the container enclosure are measured and the variation of heat transfer coefficient with the volume fraction of the nanoparticles is shown. According to our results, the heat transfer coefficient of nanofluids enhanced at low volume fractions while with further increase in the volume fraction of nanoparticles it decreased as a result of the increase in viscosity. The results show that in comparison with de-ionized water the heat transfer coefficient of nanofluids containing 0.1% volume fraction nanoparticles had a 16.0% enhancement but for a 3.0% volume fraction it had a 24.0% decrease.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 15
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The steady state heat transfer and flow resistance performance in cosine style runners with different amplitudes are studied numerically and experimentally in this paper. The results show that: When the Reynolds numbers (〈em〉Re〈/em〉) range from 1210 to 5080, the core volume goodness factor (〈em〉η〈/em〉〈sub〉o〈/sub〉〈em〉h〈/em〉〈sub〉std〈/sub〉〈em〉α〈/em〉) is used to compare the overall heat transfer performance of the two runners, and the 〈em〉η〈/em〉〈sub〉o〈/sub〉〈em〉h〈/em〉〈sub〉std〈/sub〉〈em〉α〈/em〉 value in the cosine style runner is 7–25% larger than that of the equal cross section runner, so that the cosine style runner has better overall heat transfer enhancement performance. When the amplitudes (2〈em〉A〈/em〉) range from 5 to 9 mm, with the decrease of amplitude, the overall heat transfer performance is getting better. At the same amplitude, the convective heat transfer performance gradually increases as the inlet height (〈em〉F〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉) decreases; with the increase of 〈em〉Re〈/em〉, the thickness of the thermal and velocity boundary layers are both decreasing. Based on the field synergy principle, the heat transfer enhancement mechanisms with different parameters are evaluated, and we conclude that the smaller the amplitude is, its field synergy is better.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 16
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉A simplified and efficient hydrothermal model was adapted and validated with both the experiment and literature data to further investigate the mechanism and influence of different columns on thermal performance of the vapor chamber (VC). The experiment was conducted by testing a T-shaped VC under different heat loads, and the maximum error with the numerical model was about 2 K. Factors including column dimension, column number and column structures were analyzed. Results show that sintered wick ring layer could provide auxiliary liquid circulation paths, reduce the pressure drop in the fluid circulation, and provide additional heat conductive passages. The column dimension shows enhancement on heat transfer capability of VC as the area ratio in the range of 0~0.5, with a maximum decrease by about 6.45% of the thermal resistance compared with the void VC. By comparing with other column structures, copper columns with sintered wick rings were found to the optimal type for enhancing the thermal performance of VC.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 17
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Thermoacoustic engines have been recently regarded and developed as reliable, long-life, and environment-friendly engines by using experiments or mathematical models. Thermoacoustic mathematical models can be divided into two categories of linear and nonlinear. This paper introduces a coupled 1D-2D computational nonlinear model of heat and flow fields inside loaded standing-wave thermoacoustic engines. On the one hand, the computational cost of the present model is much lower than that of full CFD models whose computational domain contains the entire engine. On the other hand, it does not have the limitation of uniform global cross section as the simplified numerical models do. In addition to the coupled nonlinear model, another simulation based on linear thermoacoustic theory (LTA) has been performed. The model has been well validated using previous experimental data and compared with the results of LTA. Subsequently, the temperature and pressure distributions, the mean acoustic power, and heat transfer and volume flow rate distributions have been presented and discussed. This model is extendable to many other systems whose some parts have negligible multidimensional effects and the other parts have considerable ones.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 18
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The requirement of fresh drinking water is one of the most severe problems all over the globe. The humidification dehumidification systems have shown promising outcomes while being used for water desalination. The performance of humidification-dehumidification water desalination systems is generally presented in the form of productivity of the humidifier or dehumidifier. Humidification being the predecessor process plays a crucial role in the performance of the Humidification - Dehumidification system. This work presents the theoretical and experimental investigation of bubbler humidifier. The performance of the bubbler humidifier is studied under various operation conditions such as: hole diameter, bubble column height, air mass flow rate, temperature of air and temperature of water inside the humidification chamber. A mechanistic model for bubbler humidifier is presented and validated with the experimental results. The Relative Humidity (RH) of air was achieved in the range of 68% to 97% for various operation conditions while the highest RH of air was recorded 97% for 1 mm of hole diameter, 7 g/s of mass flow rate of air, 60 °C of temperature of water, 48 °C of temperature of air, 7 cm of Height of water Column.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 19
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The effect of the addition of different concentrations of Cu〈sup〉2+〈/sup〉, Fe〈sup〉2+〈/sup〉, and Fe〈sup〉3+〈/sup〉 on the micromorphology and crystalline structure of CaCO〈sub〉3〈/sub〉 fouling was studied using the VHX-500FE digital microscope and X-ray diffraction. Results indicate that the fouling morphology becomes stubby and forms a cluster and the fouling color deepens with the increase in the concentration of metal ions. Furthermore, the relative content of aragonite increases and that of calcite decreases. Fe〈sup〉2+〈/sup〉 plays a more important role in the inhibition of calcite than Fe〈sup〉3+〈/sup〉 when scaling occurs in the boiling system under the condition of atmospheric environment. The reason may be that O〈sub〉2〈/sub〉 participates in the inhibition process. Fe〈sup〉2+〈/sup〉 and Fe〈sup〉3+〈/sup〉 promote atomic transition and crystal defects, and this condition changes the absorption wavelength of fouling. Carbon steel and copper samples were immersed in test solution for 28 h as a comparative experiment. This experiment indicates that corrosion may release metal ions, which further affect the fouling morphology and phase component content in the long-term fouling process. In conclusion, fouling weight method for measuring anti-fouling property can only be used to compare materials with similar anti-corrosion property.〈/p〉
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  • 20
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper critically reviews the existing theoretical models of heat transfer prediction in condensing inside plain tubes. More than 20 theoretical methods and correlations for heat transfer prediction during different modes of condensate film flow and phase distribution are considered. Lack of prior substantiation of correct application of different turbulent viscosity models for heat transfer calculation in condensing with and without influence of interfacial shear stress has been noted. The existing discrepancy of ±10% between different theoretical methods for heat transfer prediction during fully developed turbulence flow of condensate film without predominant influence of vapour velocity is shown. The dependence of theoretical methods on accuracy of frictional pressure drop determination in condensing with predominant influence of vapour velocity is highlighted. The method by Bae and others (1969) is recommended as the most correct theoretical method for prediction of heat transfer coefficients in annular flow of the phases in various heat exchangers, particularly in the evaporative systems of thermal desalinating plants, air conditioning systems, safety systems of reactors, heaters of power plants and condensers of cooling equipment.〈/p〉
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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