The Experts below are selected from a list of 28536 Experts worldwide ranked by ideXlab platform
Ehsan Roohi - One of the best experts on this subject based on the ideXlab platform.
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investigation of cold to hot transfer and thermal Separation Zone through nano step geometries
Physics of Fluids, 2015Co-Authors: Amirmehran Mahdavi, Ehsan RoohiAbstract:Nanosteps form once nanochannels of various diameters connect to each other. The focus of this paper is to investigate the heat transfer and hydro/thermal field behavior in nanostep geometries using direct simulation Monte Carlo. The effects of the hydrodynamics Separation on the pressure field and heat lines are reported, i.e., we show that the length of the hydrodynamics Separation Zone is different from the positive pressure gradient and thermal Separation Zones. Interestingly, cold to hot transfer is observed when the wall temperatures and inlet temperature are close to each other. We show that cold to hot heat transfer appears due to the interplay between the higher order term of the heat flux formula, which is a function of the second derivate of the velocity, with the Fourier term; the cold to hot transfer effect is omitted as the wall temperature or Knudsen number increases. In addition, the impact of different parameters, such as pressure ratio, Knudsen number, and wall temperature adjacent to th...
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Investigation of cold-to-hot transfer and thermal Separation Zone through nano step geometries
Physics of Fluids, 2015Co-Authors: Amirmehran Mahdavi, Ehsan RoohiAbstract:Nanosteps form once nanochannels of various diameters connect to each other. The focus of this paper is to investigate the heat transfer and hydro/thermal field behavior in nanostep geometries using direct simulation Monte Carlo. The effects of the hydrodynamics Separation on the pressure field and heat lines are reported, i.e., we show that the length of the hydrodynamics Separation Zone is different from the positive pressure gradient and thermal Separation Zones. Interestingly, cold to hot transfer is observed when the wall temperatures and inlet temperature are close to each other. We show that cold to hot heat transfer appears due to the interplay between the higher order term of the heat flux formula, which is a function of the second derivate of the velocity, with the Fourier term; the cold to hot transfer effect is omitted as the wall temperature or Knudsen number increases. In addition, the impact of different parameters, such as pressure ratio, Knudsen number, and wall temperature adjacent to the Separation Zone, are investigated. The dependence of the mass flow rate and the length of the Separation Zone on the wall temperature and the channel pressure ratio is considered. We show that Knudsen minimum is not observed in the step geometry for both isothermal and non-isothermal wall conditions.
Joseph Mankelow - One of the best experts on this subject based on the ideXlab platform.
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Examining the influence of settlement morphology and Separation Zones policies on the availability of shallow coal resources in the United Kingdom
Applied Geography, 2017Co-Authors: E.j. Bee, Joseph MankelowAbstract:In 2013, demand for coal in the UK was 60 million tonnes. Of this, 12.7 million tonnes (21%) came from indigenous sources; the majority of which was from surface mining (8.6 million tonnes). Many planning applications for surface mining of coal and the coal extraction that follows, are often a source of conflict with the communities who live within shallow coalfield areas. Policies which enforce a gap, or ‘Separation Zone’, between communities and surface coal mining operations exist in Wales and Scotland, but do not exist in England. This paper examines the effect of applying Separation Zones on the availability of shallow coal resources within two study areas; one within the South Wales Coalfield, the other within the Midlands Coalfield (comprising the Yorkshire, Nottinghamshire and North Derbyshire Coalfield areas). Density profiles and a shape-index algorithm are used to compare and contrast settlement morphology (i.e. shape or footprint) and distribution to determine whether they have a bearing on the areal extent of any potential Separation Zone applied. The implications on the availability of shallow coal resources of applying different Separation Zone distances around settlements within these two areas are explored. Results reveal that although the settlement morphology is important in determining the area of the Separation Zone, and has greatest influence in the South Wales Coalfield, the area of coal resource sterilised by the application of Separation Zones is greatest in the Midlands Coalfield due to it having a higher proportion of urban development situated on the surface extent of the shallow coal resource.
E.j. Bee - One of the best experts on this subject based on the ideXlab platform.
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Examining the influence of settlement morphology and Separation Zones policies on the availability of shallow coal resources in the United Kingdom
Applied Geography, 2017Co-Authors: E.j. Bee, Joseph MankelowAbstract:In 2013, demand for coal in the UK was 60 million tonnes. Of this, 12.7 million tonnes (21%) came from indigenous sources; the majority of which was from surface mining (8.6 million tonnes). Many planning applications for surface mining of coal and the coal extraction that follows, are often a source of conflict with the communities who live within shallow coalfield areas. Policies which enforce a gap, or ‘Separation Zone’, between communities and surface coal mining operations exist in Wales and Scotland, but do not exist in England. This paper examines the effect of applying Separation Zones on the availability of shallow coal resources within two study areas; one within the South Wales Coalfield, the other within the Midlands Coalfield (comprising the Yorkshire, Nottinghamshire and North Derbyshire Coalfield areas). Density profiles and a shape-index algorithm are used to compare and contrast settlement morphology (i.e. shape or footprint) and distribution to determine whether they have a bearing on the areal extent of any potential Separation Zone applied. The implications on the availability of shallow coal resources of applying different Separation Zone distances around settlements within these two areas are explored. Results reveal that although the settlement morphology is important in determining the area of the Separation Zone, and has greatest influence in the South Wales Coalfield, the area of coal resource sterilised by the application of Separation Zones is greatest in the Midlands Coalfield due to it having a higher proportion of urban development situated on the surface extent of the shallow coal resource.
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Investigating the influence of settlement pattern and morphology on the sterilisation of shallow coal resources
2010Co-Authors: E.j. Bee, L. NoakesAbstract:This report assesses the impact of introducing Separation Zones around urban areas on shallow coal resources. It also provides an assessment of settlement pattern using spatial statistics and an evaluation of settlement morphology (i.e. physical form or shape) based on a pre-existing density profile methodology. Two study areas have been selected for comparison: the Midlands Coalfield (comprising shallow coal resource within the Yorkshire, Nottinghamshire and North Derbyshire Coalfields) and the South Wales Coalfield. The analysis conducted in this report shows that the settlement pattern within the South Wales Coalfield study area is generally more clustered, and settlements tend to be elongate (or linear) in morphology. This is a result of the topography (steep sided valleys) in this area. In contrast, settlements in the Midlands Coalfield study area are more nucleated, or equidimensional, in morphology and more evenly dispersed over the study area. The research shows that settlement morphology can influence the size of the area of a Separation Zone. Settlements which are elongate are likely to have larger Separation Zones (in area) than equivalent sized settlements which are more equidimensional in morphology. The research also shows that the relative effect of a 500 m Separation Zone around urban areas in the South Wales Coalfield increases the influence of the urban area by 659.6 % (i.e. from 169.74 km2 to 1119.61 km2). This is significantly higher than in the Midlands Coalfield study area, where the influence of the urban area when a 500 m Separation Zone is applied increases by 402.8 % (i.e. from 496.49 km2 to 1999.75 km2). Of the two study areas, the greatest overall impact on the sterilisation of shallow coal resources from urban development is seen within the Midlands Coalfield study area. This is not a consequence of the contrasting settlement patterns; rather it results from the greater proportion of urban areas within the Midlands Coalfield. Urban development encompasses 496.49 km2 (17.2 %) of the Midlands Coalfield whereas in South Wales, urban development encompasses 169.74 km2 (6.7 %) of the study area. Of the total urban development within each study area, a greater amount lies within the surface extent of shallow coal resource in the Midlands Coalfield (423.17 km2 or 85.2 %) than in the South Wales Coalfield study area (86.14 km2 or 50.7 %). The effect, therefore, of placing a Separation Zone of 500 m around urban areas within the Midlands Coalfield is that a greater amount (1727.85 km2 or 72.2 %) of the total surface extent of the shallow coal resource is sterilised than in the South Wales Coalfield study area (563.28 km2 or 52.8 %). The study concludes that a number of factors influence the area of a Separation Zone and thus the amount of shallow coal resource sterilised from urban development: 1. The distribution (settlement pattern) of settlements within the coalfield. 2. The shape of an individual settlement (settlement morphology). 3. The extent of the urban area lying within the coalfield. However, given two study areas with equally distributed and sized urban areas, the morphology (shape) of the urban settlements may have greatest influence on the size of the Separation Zone. This could explain why settlements within the South Wales Coalfield have a greater relative impact on Separation Zone area than settlements in the Midlands Coalfield.
Amirmehran Mahdavi - One of the best experts on this subject based on the ideXlab platform.
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investigation of cold to hot transfer and thermal Separation Zone through nano step geometries
Physics of Fluids, 2015Co-Authors: Amirmehran Mahdavi, Ehsan RoohiAbstract:Nanosteps form once nanochannels of various diameters connect to each other. The focus of this paper is to investigate the heat transfer and hydro/thermal field behavior in nanostep geometries using direct simulation Monte Carlo. The effects of the hydrodynamics Separation on the pressure field and heat lines are reported, i.e., we show that the length of the hydrodynamics Separation Zone is different from the positive pressure gradient and thermal Separation Zones. Interestingly, cold to hot transfer is observed when the wall temperatures and inlet temperature are close to each other. We show that cold to hot heat transfer appears due to the interplay between the higher order term of the heat flux formula, which is a function of the second derivate of the velocity, with the Fourier term; the cold to hot transfer effect is omitted as the wall temperature or Knudsen number increases. In addition, the impact of different parameters, such as pressure ratio, Knudsen number, and wall temperature adjacent to th...
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Investigation of cold-to-hot transfer and thermal Separation Zone through nano step geometries
Physics of Fluids, 2015Co-Authors: Amirmehran Mahdavi, Ehsan RoohiAbstract:Nanosteps form once nanochannels of various diameters connect to each other. The focus of this paper is to investigate the heat transfer and hydro/thermal field behavior in nanostep geometries using direct simulation Monte Carlo. The effects of the hydrodynamics Separation on the pressure field and heat lines are reported, i.e., we show that the length of the hydrodynamics Separation Zone is different from the positive pressure gradient and thermal Separation Zones. Interestingly, cold to hot transfer is observed when the wall temperatures and inlet temperature are close to each other. We show that cold to hot heat transfer appears due to the interplay between the higher order term of the heat flux formula, which is a function of the second derivate of the velocity, with the Fourier term; the cold to hot transfer effect is omitted as the wall temperature or Knudsen number increases. In addition, the impact of different parameters, such as pressure ratio, Knudsen number, and wall temperature adjacent to the Separation Zone, are investigated. The dependence of the mass flow rate and the length of the Separation Zone on the wall temperature and the channel pressure ratio is considered. We show that Knudsen minimum is not observed in the step geometry for both isothermal and non-isothermal wall conditions.
V. I. Terekhov - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of heat transfer in the Separation Zone behind a backward-facing step in the presence of tabs
Thermophysics and Aeromechanics, 2019Co-Authors: A. Yu. D’yachenko, V. L. Zhdanov, Ya. I. Smul’skii, V. I. TerekhovAbstract:The paper presents the experimental data on distribution of static pressure and heat transfer in a Separation Zone behind a backward-facing step equipped with vortex generators. The size and gaps between generators (tabs) of rec-tangular shape were varied in experiments. Experimental results were compared with two limiting cases: a smooth step (no tabs), and a step with a solid fin. The strongest influence on flow and heat transfer from the set of installed tabs was observed within the recirculation Zone just behind the step base. The tabs allocated at the step edge resulted in the displacement of the Nusselt number maximum to the step base that caused the enhancement of a local and ave-rage heat transfer.
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Friction and Heat Transfer in a Laminar Separated Flow behind a Rectangular Step with Porous Injection or Suction
Journal of Applied Mechanics and Technical Physics, 2006Co-Authors: S. R. Batenko, V. I. TerekhovAbstract:Results of a numerical study of a laminar separated flow behind a rectangular step on a porous surface with uniform injection or suction are described. Two cases are considered: an unconfined flow past a step and flow evolution in a confined channel (duct). It is shown that mass transfer on the surface causes strong changes in the flow structure and substantially affects the position of the reattachment point, as well as friction and heat transfer. More intense injection leads first to an increase in the Separation-Zone length and then to its rapid vanishing due to boundary-layer displacement. Vice versa, suction at high Reynolds numbers Re_ s > 100 reduces the Separation-Zone length. The duct flow has a complicated distribution of friction and heat-transfer coefficients along the porous surface owing to the coupled effect of the transverse flow of the substance and changes in the main flow velocity due to mass transfer.
