The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Gang Zhou - One of the best experts on this subject based on the ideXlab platform.
-
Synthetical optimization of Hydraulic Radius and acoustic field for thermoacoustic cooler
Energy Conversion and Management, 2009Co-Authors: Huifang Kang, Gang ZhouAbstract:Abstract It is well known that the acoustic field and the Hydraulic Radius of the regenerator play key roles in thermoacoustic processes. The optimization of Hydraulic Radius strongly depends on the acoustic field in the regenerator. This paper investigates the synthetical optimization of Hydraulic Radius and acoustic field which is characterized by the ratio of the traveling wave component to the standing wave component. In this paper, we discussed the heat flux, cooling power, temperature gradient and coefficient of performance of thermoacoustic cooler with different combinations of Hydraulic Radiuses and acoustic fields. The calculation results show that, in the cooler’s regenerator, due to the acoustic wave, the heat is transferred towards the pressure antinodes in the pure standing wave, while the heat is transferred in the opposite direction of the wave propagation in the pure traveling wave. The better working condition for the regenerator appears in the traveling wave phase region of the like-standing wave, where the directions of the heat transfer by traveling wave component and standing wave component are the same. Otherwise, the small Hydraulic Radius is not a good choice for acoustic field with excessively high ratio of traveling wave, and the small Hydraulic Radius is only needed by the traveling wave phase region of like-standing wave.
-
Optimizing Hydraulic Radius and acoustic field of the thermoacoustic engine
Cryogenics, 2008Co-Authors: Huifang Kang, Gang ZhouAbstract:It is well known that the acoustic field and the Hydraulic Radius of the regenerator play key roles in thermoacoustic processes. The optimization of Hydraulic Radius strongly depends on the acoustic field in the regenerator. This paper investigates the synthetical optimization of the Hydraulic Radius and the acoustic field which is characterized by the ratio of the traveling wave component over the standing wave component. In this paper, the normalized expressions of acoustic power gain and second law efficiency are derived and calculated, and then some useful calculated results are discussed. Some conclusions have been obtained, which are of significance to explain the optimum work conditions of existing engines and to guide the designs of new thermoacoustic devices. Finally, the operation factor of regenerator is discussed, which is a dimensionless parameter defined in this paper and highly relates to the working condition of the regenerator.
D B Silin - One of the best experts on this subject based on the ideXlab platform.
-
shape factor and Hydraulic conductance in noncircular capillaries i one phase creeping flow
Journal of Colloid and Interface Science, 2001Co-Authors: Tadeusz W Patzek, D B SilinAbstract:Abstract We use the Mason–Morrow shape factor, i.e., a dimensionless Hydraulic Radius, and corner half-angles to capture the geometry of noncircular capillaries pertinent to a physically adequate pore network description of porous media. We give analytic expressions for random corner half-angles that satisfy a given shape factor calculated from the microscopic images of pore space. We demonstrate that use of the shape factor leads to particularly simple expressions for the Hydraulic conductance in single-phase flow through noncircular capillaries. In particular, we obtain the Hydraulic conductances of arbitrary triangular ducts semianalytically, using conformal mapping. The conductances of equilateral triangular, rectangular, and elliptic ducts are calculated analytically.
-
regular articleshape factor and Hydraulic conductance in noncircular capillaries i one phase creeping flow
Journal of Colloid and Interface Science, 2001Co-Authors: Tadeusz W Patzek, D B SilinAbstract:We use the Mason–Morrow shape factor, i.e., a dimensionless Hydraulic Radius, and corner half-angles to capture the geometry of noncircular capillaries pertinent to a physically adequate pore network description of porous media. We give analytic expressions for random corner half-angles that satisfy a given shape factor calculated from the microscopic images of pore space. We demonstrate that use of the shape factor leads to particularly simple expressions for the Hydraulic conductance in single-phase flow through noncircular capillaries. In particular, we obtain the Hydraulic conductances of arbitrary triangular ducts semianalytically, using conformal mapping. The conductances of equilateral triangular, rectangular, and elliptic ducts are calculated analytically.
Tadeusz W Patzek - One of the best experts on this subject based on the ideXlab platform.
-
shape factor and Hydraulic conductance in noncircular capillaries i one phase creeping flow
Journal of Colloid and Interface Science, 2001Co-Authors: Tadeusz W Patzek, D B SilinAbstract:Abstract We use the Mason–Morrow shape factor, i.e., a dimensionless Hydraulic Radius, and corner half-angles to capture the geometry of noncircular capillaries pertinent to a physically adequate pore network description of porous media. We give analytic expressions for random corner half-angles that satisfy a given shape factor calculated from the microscopic images of pore space. We demonstrate that use of the shape factor leads to particularly simple expressions for the Hydraulic conductance in single-phase flow through noncircular capillaries. In particular, we obtain the Hydraulic conductances of arbitrary triangular ducts semianalytically, using conformal mapping. The conductances of equilateral triangular, rectangular, and elliptic ducts are calculated analytically.
-
regular articleshape factor and Hydraulic conductance in noncircular capillaries i one phase creeping flow
Journal of Colloid and Interface Science, 2001Co-Authors: Tadeusz W Patzek, D B SilinAbstract:We use the Mason–Morrow shape factor, i.e., a dimensionless Hydraulic Radius, and corner half-angles to capture the geometry of noncircular capillaries pertinent to a physically adequate pore network description of porous media. We give analytic expressions for random corner half-angles that satisfy a given shape factor calculated from the microscopic images of pore space. We demonstrate that use of the shape factor leads to particularly simple expressions for the Hydraulic conductance in single-phase flow through noncircular capillaries. In particular, we obtain the Hydraulic conductances of arbitrary triangular ducts semianalytically, using conformal mapping. The conductances of equilateral triangular, rectangular, and elliptic ducts are calculated analytically.
Men Baohui - One of the best experts on this subject based on the ideXlab platform.
-
an ecological Hydraulic Radius approach to estimate the instream ecological water requirement
Progress in Natural Science, 2007Co-Authors: Liu Changming, Men BaohuiAbstract:This essay defines the concepts of ecological flow velocity as well as ecological Hydraulic Radius (EHR) and proposes an ecological Hydraulic Radius approach (EHRA) which considers both the watercourse information (including Hydraulic Radius, roughness coefficient and Hydraulic gradient) and the required stream velocity necessary for maintenance of certain ecological functions all together. The key parameter of EHRA is to fix the watercourse cross-sectional flow area corresponding to EHR, by which the relation between parabola shaped cross-sectional flow area and Hydraulic Radius is deduced. The EHRA not only meets the requirement of flow velocity for adequate fish spawning migration, but also is applicable to the ecological flows in regard with other ecological issues (such as the calculation of the instream flow requirements for transporting sediment and for pollution self-purification, etc.). This essay has illuminated the computational process taking the estimation of ecological water requirement of Zhuba Hydrologyical Station watercourse in Niqu branch of the Yalong River as an example. Additionally, we compare EHRA with Tennant approach.) The result shows that the Zhuba Hydrological Station ecological water requirement calculated by EHRA lies between the minimum and favorable ecological water requirement calculated by the Tennant approach. This is due to the fact that the ecological flow velocity (such as the fish spawning migration flow velocity) was taken into consideration, producing results applicable to the practical situation.
Zbigniew Koza - One of the best experts on this subject based on the ideXlab platform.
-
tortuosity porosity relation in porous media flow
Physical Review E, 2008Co-Authors: Maciej Matyka, Arzhang Khalili, Zbigniew KozaAbstract:We study numerically the tortuosity-porosity relation in a microscopic model of a porous medium arranged as a collection of freely overlapping squares. It is demonstrated that the finite-size, slow relaxation and discretization errors, which were ignored in previous studies, may cause significant underestimation of tortuosity. The simple tortuosity calculation method proposed here eliminates the need for using complicated, weighted averages. The numerical results presented here are in good agreement with an empirical relation between tortuosity (T) and porosity (varphi) given by T-1 proportional, variantlnvarphi , that was found by others experimentally in granule packings and sediments. This relation can be also written as T-1 proportional, variantRSvarphi with R and S denoting the Hydraulic Radius of granules and the specific surface area, respectively. Applicability of these relations appears to be restricted to porous systems of randomly distributed obstacles of equal shape and size.
-
tortuosity porosity relation in porous media flow
Physical Review E, 2008Co-Authors: Maciej Matyka, Arzhang Khalili, Zbigniew KozaAbstract:We study numerically the tortuosity-porosity relation in a microscopic model of a porous medium arranged as a collection of freely overlapping squares. It is demonstrated that the finite-size, slow relaxation and discretization errors, which were ignored in previous studies, may cause significant underestimation of tortuosity. The simple tortuosity calculation method proposed here eliminates the need for using complicated, weighted averages. The numerical results presented here are in good agreement with an empirical relation between tortuosity $(T)$ and porosity $(\ensuremath{\phi})$ given by $T\ensuremath{-}1\ensuremath{\propto}\mathrm{ln}\phantom{\rule{0.2em}{0ex}}\ensuremath{\phi}$, that was found by others experimentally in granule packings and sediments. This relation can be also written as $T\ensuremath{-}1\ensuremath{\propto}RS∕\ensuremath{\phi}$ with $R$ and $S$ denoting the Hydraulic Radius of granules and the specific surface area, respectively. Applicability of these relations appears to be restricted to porous systems of randomly distributed obstacles of equal shape and size.
