The Experts below are selected from a list of 66843 Experts worldwide ranked by ideXlab platform
Apurba Layek - One of the best experts on this subject based on the ideXlab platform.
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Nusselt Number and friction factor correlation of solar air heater having winglet type vortex generator over absorber plate
Solar Energy, 2020Co-Authors: Amit Kumar, Apurba LayekAbstract:Abstract The experimentation has been done using the winglet type vortex generator as a roughness element above the absorber surface of a solar air heater (SAH) system. Different geometry-based roughness parameters have been considered such as relative roughness pitch (Pi/e) value of 5–12, relative roughness width (Ww/w) value of 3–7, angle of attack (α) value of 300-750 and the flowing fluid Reynolds Number diversified between 3000 and 22,000 respectively and its effect on Nusselt Number (Nuu) and friction factor (fr1) were studied. In order to achieve its optimum condition, the Nusselt Number (Nuu) and friction factor (fr1) are analyzed for the roughness parameters to obtain the best overall performance and the required values are compared with the smooth type duct under similar flowing condition. Using regression analysis, correlations have been expanded for Nusselt Number (Nuu) and friction component (fr1) in terms of Reynolds Number (Re) and with different parametric condition which is considered to be satisfactory when compared with the experimental results.
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Nusselt Number-friction characteristic for a twisted rib roughened rectangular duct using liquid crystal thermography
Experimental Thermal and Fluid Science, 2018Co-Authors: Anup Kumar, Apurba LayekAbstract:Abstract Liquid crystal thermography technique is applied over a wide wall of a rectangular channel having twisted rib roughness to evaluate heat transfer distribution. The temperature distribution can be easily visualized easily as color pattern obtained by a CCD camera. The captured color pattern is digitized and converted to HIS (Hue, Saturation and Intensity) from RGB (red, Green and Blue). In this study the effect of different roughness parameters such as relative roughness pitch, twist ratio and rib inclination angle on heat transfer coefficient and friction factor are investigated. The range of Reynolds Number and aspect ratio of the duct is selected those are most suitable for solar air heater. It is observed that relative roughness pitch of 8 shows the maximum heat transfer while friction factor decreases with increase in relative roughness pitch. The effect of twist ratio is to create the jet formation on the downstream side of the ribs, which creates vigorous mixing to increase in heat transfer. The increase in twist ratio decreases the Number of jets formed and the Nusselt Number, while friction factor increases. The rib inclination to the main flow generates secondary flow, increases turbulence level as well as Nusselt Number. The secondary flow increases with increase in inclination angle to create maxima in Nusselt Number at an angle of 60°. The friction factor increases with increase in rib inclination angle.
Vikash Kumar - One of the best experts on this subject based on the ideXlab platform.
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Nusselt Number and friction factor correlations of three sides concave dimple roughened solar air heater
Renewable Energy, 2019Co-Authors: Vikash KumarAbstract:Abstract Performance analysis of roughened solar air heater becomes hectic due to absence of statistical correlation for heat transfer and friction factor. For understanding flow behavior, researchers have developed statistical correlations for different roughness geometries. This paper presents the outcome of experimental investigations upon 1 & 3-sides concave dimple roughened ducts. The results are presented as variation in Nusselt Number & friction factor with Reynolds Number. The geometrical & flow parameters has been varied as relative dimple pitch (p/e), relative dimple height (e/Dh), relative dimple depth (e/d) & Reynolds Number in the range of 8–15, 0.018–0.045, 1–2 & 2000–13500 respectively. Statistical correlations for Nusselt Number and friction factor in terms of roughness and flow parameters were derived based on data collected from experiment. Optimized value of flow & roughness parameter yielding maximum performance is determined. The maximum enhancement in Nusselt Number for varying relative dimple pitch, relative dimple height & relative dimple depth was respectively of the order of 2.6–3.55, 1.91 to 3.42, 3.09 to 3.94 times and that of friction factor was of the order of 1.62–2.79, 1.52 to 2.34 and 2.21 to 2.56 times over those of 1-side roughened ones.
Ismail Teke - One of the best experts on this subject based on the ideXlab platform.
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New approach relevant to floor Nusselt Number in floor heating system
Energy Conversion and Management, 2008Co-Authors: Refet Karadağ, Ismail TekeAbstract:In this study, the Nusselt Number over the floor is analysed numerically for different thermal conditions in a floor heated room. A new equation related to floor Nusselt Number is developed. In the literature, there have been a Number of equations, different from each other and appropriate only for the conditions at which the studies were performed, have been presented. While the mentioned equations were dependent only on the floor Rayleigh Number, numerical data obtained in the current study show that the floor Nusselt Number depends not only on the floor Rayleigh Number but also the wall and ceiling Rayleigh Numbers. Therefore, the new equation developed in the current study is a function of the Rayleigh Numbers over the floor, wall and ceiling surfaces. This equation is compared with those found in the literature. It is seen that while the maximum deviation from the numerical data is 35% for the equations given in the literature, it is only 10% for the new equation. Therefore, the given equation is verified to be more reliable and appropriate for the calculation of Nusselt Number.
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Investigation of floor Nusselt Number in floor heating system for insulated ceiling conditions
Energy Conversion and Management, 2007Co-Authors: Refet Karadağ, Ismail TekeAbstract:In this study, in a floor heated room, natural convection heat transfer over the floor is analysed numerically for different thermal conditions. An equation relevant to Nusselt Number over the floor has been obtained by using the numerical data. Different equations are given in the literature. They consider the effect of floor Rayleigh Number while neglecting the effect of wall and ceiling thermal conditions. Numerical data obtained in this study show that the Nusselt Number over the floor depends on not only the floor Rayleigh Number but also the wall Rayleigh Number (for insulated ceiling conditions). The equations given in the literature are different from each other due to their not considering the effect of wall and ceiling Rayleigh Numbers. This difference between the equations may be eliminated by obtaining an equation containing the effect of floor, wall and ceiling Rayleigh Numbers. In this new approach, an equation relevant to the floor Nusselt Number that depends on the floor and wall Rayleigh Numbers has been obtained in the floor heating system for insulated ceiling conditions. The equation obtained in this study has been compared with the equations given in the literature. It has been seen that the equation obtained in this study matches the numerical values under more extensive thermal conditions than the equations given in the literature. The maximum deviation for the equations given in the literature is 35%, but in the current study, the maximum deviation has been found to be 10%. As a result, it is more convenient to use the equation found in the new approach as a function of Rayleigh Number over the floor and wall for insulated ceiling conditions.
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A numerical investigation on effects of ceiling and floor surface temperatures and room dimensions on the Nusselt Number for a floor heating system
International Communications in Heat and Mass Transfer, 2007Co-Authors: Refet Karadağ, Ismail Teke, Hüsamettin BulutAbstract:Abstract In this study, the effect of ceiling and floor surface temperatures and room dimensions on the Nusselt Number over the floor of a floor heating system has been investigated numerically. The variation of the Nusselt Number with Rayleigh Number has been analyzed under constant wall temperature condition for different ceiling temperatures (10–25 °C) and room dimensions. It has been seen that when the room dimensions and temperature difference between the ceiling and interior air are increased, the Nusselt Number over the floor increases as well. The numerical results have been compared with the correlations given in the literature. It has been seen that the correlations available in the literature are valid only for given thermal conditions and room dimensions. The results calculated from the correlations which do not consider the effects of ceiling and floor surface temperatures deviate up to 35% than the results of this numerical study carried out for different ceiling and floor surface temperatures and room dimensions. Therefore, a new correlation for Nusselt Number over the floor, which contain the influence of thermal conditions and all of room dimensions must be discovered.
Refet Karadağ - One of the best experts on this subject based on the ideXlab platform.
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New approach relevant to floor Nusselt Number in floor heating system
Energy Conversion and Management, 2008Co-Authors: Refet Karadağ, Ismail TekeAbstract:In this study, the Nusselt Number over the floor is analysed numerically for different thermal conditions in a floor heated room. A new equation related to floor Nusselt Number is developed. In the literature, there have been a Number of equations, different from each other and appropriate only for the conditions at which the studies were performed, have been presented. While the mentioned equations were dependent only on the floor Rayleigh Number, numerical data obtained in the current study show that the floor Nusselt Number depends not only on the floor Rayleigh Number but also the wall and ceiling Rayleigh Numbers. Therefore, the new equation developed in the current study is a function of the Rayleigh Numbers over the floor, wall and ceiling surfaces. This equation is compared with those found in the literature. It is seen that while the maximum deviation from the numerical data is 35% for the equations given in the literature, it is only 10% for the new equation. Therefore, the given equation is verified to be more reliable and appropriate for the calculation of Nusselt Number.
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Investigation of floor Nusselt Number in floor heating system for insulated ceiling conditions
Energy Conversion and Management, 2007Co-Authors: Refet Karadağ, Ismail TekeAbstract:In this study, in a floor heated room, natural convection heat transfer over the floor is analysed numerically for different thermal conditions. An equation relevant to Nusselt Number over the floor has been obtained by using the numerical data. Different equations are given in the literature. They consider the effect of floor Rayleigh Number while neglecting the effect of wall and ceiling thermal conditions. Numerical data obtained in this study show that the Nusselt Number over the floor depends on not only the floor Rayleigh Number but also the wall Rayleigh Number (for insulated ceiling conditions). The equations given in the literature are different from each other due to their not considering the effect of wall and ceiling Rayleigh Numbers. This difference between the equations may be eliminated by obtaining an equation containing the effect of floor, wall and ceiling Rayleigh Numbers. In this new approach, an equation relevant to the floor Nusselt Number that depends on the floor and wall Rayleigh Numbers has been obtained in the floor heating system for insulated ceiling conditions. The equation obtained in this study has been compared with the equations given in the literature. It has been seen that the equation obtained in this study matches the numerical values under more extensive thermal conditions than the equations given in the literature. The maximum deviation for the equations given in the literature is 35%, but in the current study, the maximum deviation has been found to be 10%. As a result, it is more convenient to use the equation found in the new approach as a function of Rayleigh Number over the floor and wall for insulated ceiling conditions.
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A numerical investigation on effects of ceiling and floor surface temperatures and room dimensions on the Nusselt Number for a floor heating system
International Communications in Heat and Mass Transfer, 2007Co-Authors: Refet Karadağ, Ismail Teke, Hüsamettin BulutAbstract:Abstract In this study, the effect of ceiling and floor surface temperatures and room dimensions on the Nusselt Number over the floor of a floor heating system has been investigated numerically. The variation of the Nusselt Number with Rayleigh Number has been analyzed under constant wall temperature condition for different ceiling temperatures (10–25 °C) and room dimensions. It has been seen that when the room dimensions and temperature difference between the ceiling and interior air are increased, the Nusselt Number over the floor increases as well. The numerical results have been compared with the correlations given in the literature. It has been seen that the correlations available in the literature are valid only for given thermal conditions and room dimensions. The results calculated from the correlations which do not consider the effects of ceiling and floor surface temperatures deviate up to 35% than the results of this numerical study carried out for different ceiling and floor surface temperatures and room dimensions. Therefore, a new correlation for Nusselt Number over the floor, which contain the influence of thermal conditions and all of room dimensions must be discovered.
A. K. Cousins - One of the best experts on this subject based on the ideXlab platform.
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On the Nusselt Number in Heat Transfer Between Multiple Parallel Blood Vessels
Journal of biomechanical engineering, 1997Co-Authors: A. K. CousinsAbstract:Arrays of two or more parallel blood vessels in a tissue matrix have been studied extensively in the context of bioheat transfer. The average vessel Nusselt Number (based on the difference between the mixed-mean blood temperature and the average vessel surface temperature) is a crucial parameter in such studies. Various workers have noted tht in particular cases the average Nusselt Number is identical to that for fully developed flow in a single vessel in an infinite medium. In other words, the Nusselt Number is unaffected by the presence of other vessels. It is proven here that this surprising result holds true for arbitrary Number, size, flow direction, and velocity profile in the blood vessels, and for very general boundary conditions on the outer tissue boundary. A useful corollary is that the average wall temperature in a particular vessel may be found by evaluating the temperature fields due to the other vessels and the tissue boundaries at a single point, the center of the vessels in question.
