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J. S. Saini - One of the best experts on this subject based on the ideXlab platform.

  • investigation on performance enhancement due to staggered piece in a broken arc rib roughened solar air heater duct
    Renewable Energy, 2017
    Co-Authors: R S Gill, V S Hans, J. S. Saini, Sukhmeet Singh
    Abstract:

    Abstract This paper presents an experimental investigation on heat transfer and friction factor characteristics of solar air heater duct whose absorber is roughened with “broken arc rib combined with staggered rib piece”. The duct has aspect ratio of 12 and the absorber is heated with uniform heat flux while others three walls are insulated. The rib Roughness has fixed Relative staggered rib position, Relative Roughness height, Relative gap size, Relative gap position, arc angle and Relative Roughness pitch of 0.4, 0.043, 1.0, 0.65, 30° and 10 respectively. The Relative staggered rib size and Reynolds number were varied from 1 to 6 and 2000 to 16,000 respectively. The effect of staggered rib on the flow pattern has also been observed using ANSYS Academic Research CFD 15.0. The maximum enhancement in Nusselt number and friction factor over that of broken arc rib roughened duct under similar flow and boundary conditions has been found to be 2.60 and 2.27 times respectively. The corresponding enhancements over that of smooth duct are 3.06 and 2.50 times respectively. The thermo-hydraulic performance of duct roughened with present rib Roughness has been considerably enhanced and was found to be highest for Relative staggered rib size of 4.

  • heat transfer and friction factor correlations for a solar air heater duct roughened artificially with v ribs with symmetrical gaps
    Experimental Thermal and Fluid Science, 2016
    Co-Authors: Rajesh Maithani, J. S. Saini
    Abstract:

    Abstract An experimental study has been carried out for enhancement of heat transfer coefficient of a solar air heater having roughened air duct artificially roughened in the form of V-ribs with symmetrical gaps as turbulence promoter. In present work an experimental investigation of heat transfer and friction of artificial Roughness in the form of V-ribs with symmetrical gaps were investigated. The investigation encompassed Reynolds number ( Re ) ranging from 4000 to 18,000, Number of gaps ( N g ) values of 1–5, Relative gap width ( g / e ) values of 1–5, Relative Roughness pitch ( P / e ) values of 6–12, angle of attack ( α ) range of 30–75° and Relative Roughness height ( e / D ) values of 0.043. For Nusselt number ( Nu ), the maximum enhancement of the order of 3.6 times that of smooth duct has been obtained, similarly friction factor ( f ) also increases by 3.67 folds of that of the smooth duct. The rib parameters corresponding to maximum increase in Nu and f were N g  = 3, g / e  = 4, P / e  = 10 and α  = 60°. Based on the experimental data, correlations for Nu and f have been developed as function of Roughness parameters of V-ribs with symmetrical gap and flow Reynolds number.

  • thermo hydraulic performance due to Relative Roughness pitch in v down rib with gap in solar air heater duct comparison with similar rib Roughness geometries
    Renewable & Sustainable Energy Reviews, 2015
    Co-Authors: Sukhmeet Singh, Subhash Chander, J. S. Saini
    Abstract:

    Abstract This paper presents thermo-hydraulic performance comparison of rib Roughness under investigation, ‘V-down ribs with gap’ and similar reported rib Roughness geometries used in solar air heater duct. The present rib Roughness has flow-attack-angle and Relative Roughness height of 60° and 0.043, respectively. The duct has aspect ratio of 12 and the Reynolds number ranged from 3000 to 15,000. The roughened wall was uniformly heated while the remaining three walls were insulated. These boundary conditions correspond closely to those found in conventional solar air heaters. Five rib roughened plates having Relative Roughness pitch of 4, 6, 8, 10 and 12 have been tested. The Nusselt number and friction factor were found to be highest for Relative Roughness pitch of 8. Maximum enhancement in Nusselt number and friction factor has been found to be 2.70 and 2.86, respectively. Thermo-hydraulic performance parameter ranged from 1.27 to 1.93. Thermo-hydraulic comparison with similar rib geometries show that the present Roughness geometry performs better for Reynolds number range of 3000–12,000.

  • development of correlations for nusselt number and friction factor for solar air heater with roughened duct having multi v shaped with gap rib as artificial Roughness
    Renewable Energy, 2013
    Co-Authors: Anil Kuma, R P Saini, J. S. Saini
    Abstract:

    This paper presents the results of an experimental investigation of heat transfer and friction in the flow of air in rectangular ducts having multi v-shaped rib with gap Roughness on one broad wall. The investigation encompassed Reynolds number (Re) from 2000 to 20,000, Relative gap distance (Gd/Lv) values of 0.24–0.80, Relative gap width (g/e) values of 0.5–1.5, Relative Roughness height (e/D) values of 0.022–0.043, Relative Roughness pitch (P/e) values of 6–12, Relative Roughness width ratio (W/w) values of 1–10, angle of attack (α) range of 30°–75°. The optimum values of geometrical parameters of Roughness have been obtained and discussed. For Nusselt number (Nu), the maximum enhancement of the order of 6.74 times of the corresponding value of the smooth duct has been obtained, however the friction factor (f) has also been seen to increase by 6.37 times of that of the smooth duct. The rib parameters corresponding to maximum increase in Nu and f were Gd/Lv=0.69, g/e=1.0, e/D=0.043, P/e=8, W/w=6 and α=60°. Based on the experimental data, correlations for Nu and f have been developed as function of Roughness parameters of multi v-shaped with gap rib and flow Reynolds number.

  • investigations on thermo hydraulic performance due to flow attack angle in v down rib with gap in a rectangular duct of solar air heater
    Applied Energy, 2012
    Co-Authors: Sukhmeet Singh, Subhash Chander, J. S. Saini
    Abstract:

    Abstract In this investigation, thermo-hydraulic performance of rectangular ducts roughened with a new configuration of ‘V-down rib having gap’ on one wide wall is determined. Small symmetrical gap equal to rib height is created at the centre of both legs of V of continuous V-down rib. The duct has aspect ratio (AR) of 12 and the Reynolds number (Re) ranged from 3000 to 15,000. To simulate the indoor testing of solar air heater, the roughened side of rectangular duct is heated with constant heat flux electric heater while the other sides are insulated. The Roughness has Relative Roughness height of 0.043 and Relative Roughness pitch of 8. Five rib roughened plates having flow-attack-angle (α) from 30° to 75° have been tested. The thermo-hydraulic performance parameter based on equal pumping power (η), friction factor (f) and Nusselt number (Nu), were found to be highest for α = 60°. The results obtained at α = 60° were compared with those of continuous V-down rib for same rib-Roughness parameters.

Sukhmeet Singh - One of the best experts on this subject based on the ideXlab platform.

  • cfd analysis of solar air heater duct having square wave profiled transverse ribs as Roughness elements
    Solar Energy, 2018
    Co-Authors: Inderjeet Singh, Sukhmeet Singh
    Abstract:

    Abstract In this investigation, the thermal and hydraulic performance of solar air heater duct roughened with non-uniform cross-sectioned square wave profiled transverse rib is carried out in ANSYS Fluent 15.0. The 3-D investigation considered parameters as Relative Roughness pitch 4–30 and Reynolds number 3000–15,000, while Relative Roughness height has been fixed as 0.043. The turbulence model RNG k-e with enhanced wall treatment and one periodic length was selected for analysis. The CFD methodology has been validated with the experimental results available in literature. The maximum augmentation in Nusselt number and friction factor over smooth duct was found to be 2.14 times and 3.55 times respectively at Relative Roughness pitch of 10 and Reynolds number of 15,000. The heat transfer and fluid flow process are discussed and visualized using streamlines and contours. The maximum thermohydraulic performance parameter was observed to be 1.43 at Relative Roughness pitch of 10 and Reynolds number of 12,000. The thermohydraulic performance for the non-uniform rib was also observed to be more than uniform cross-sectioned rib.

  • investigations on thermo hydraulic performance of broken arc rib in a rectangular duct of solar air heater
    International Communications in Heat and Mass Transfer, 2017
    Co-Authors: R S Gill, V S Hans, Sukhmeet Singh
    Abstract:

    Abstract In present paper, solar air heater duct having aspect ratio 12 roughened with broken arc rib has been investigated. The broken arc is formed by creating symmetrical gap in continuous arc with gap width equal to Roughness height. It has been planned to investigate the influence of position of gap in arc rib on Nusselt number as well as on friction factor. For this purpose, five broken arc rib roughened plates having Relative gap position ranging 0.2–0.8 have been investigated for values of Reynolds number 2000–16000. The remaining Roughness parameters like Relative Roughness height, arc angle, and Relative Roughness pitch were taken as 0.043, 30o and 8 respectively. The presence of broken arc ribs enhanced the Nusselt number, friction factor and thermo-hydraulic performance up to 2.37, 2.55 and 1.94 respectively, compared to smooth duct. The results of ducts roughened with broken arc rib and continuous arc rib have been compared under similar flow conditions. The effect of gap in continuous arc rib on the flow pattern has also been observed using ANSYS Academic Research CFD 15.0.

  • cfd investigation on Roughness pitch variation in non uniform cross section transverse rib Roughness on nusselt number and friction factor characteristics of solar air heater duct
    Energy, 2017
    Co-Authors: Amritpal Singh, Sukhmeet Singh
    Abstract:

    Abstract In the present study, solar air heater duct roughened with non-uniform cross-section saw tooth rib has been numerically investigated for Nusselt number and friction factor. The investigation has been carried in 3-D with computational fluid dynamics software. The parameters, Reynolds number and Relative Roughness pitch ranged from 3000 to 15000 and 4 to 30 respectively. The Relative Roughness height and saw-tooth angle were 0.043 and 45° respectively. The renormalization group (RNG) k-e turbulence model was selected for analysis. At Relative Roughness pitch of 16, both the Nusselt number and friction factor were maximum for the investigated Reynolds number range. The contours of turbulent dissipation rate, turbulent kinetic energy, static temperature and static pressure have also been plotted. The maximum Nusselt number and friction factor enhancement over smooth duct was 2.18 and 3.34 respectively at Reynolds number of 15000 and Relative Roughness pitch of 16.

  • investigation on performance enhancement due to staggered piece in a broken arc rib roughened solar air heater duct
    Renewable Energy, 2017
    Co-Authors: R S Gill, V S Hans, J. S. Saini, Sukhmeet Singh
    Abstract:

    Abstract This paper presents an experimental investigation on heat transfer and friction factor characteristics of solar air heater duct whose absorber is roughened with “broken arc rib combined with staggered rib piece”. The duct has aspect ratio of 12 and the absorber is heated with uniform heat flux while others three walls are insulated. The rib Roughness has fixed Relative staggered rib position, Relative Roughness height, Relative gap size, Relative gap position, arc angle and Relative Roughness pitch of 0.4, 0.043, 1.0, 0.65, 30° and 10 respectively. The Relative staggered rib size and Reynolds number were varied from 1 to 6 and 2000 to 16,000 respectively. The effect of staggered rib on the flow pattern has also been observed using ANSYS Academic Research CFD 15.0. The maximum enhancement in Nusselt number and friction factor over that of broken arc rib roughened duct under similar flow and boundary conditions has been found to be 2.60 and 2.27 times respectively. The corresponding enhancements over that of smooth duct are 3.06 and 2.50 times respectively. The thermo-hydraulic performance of duct roughened with present rib Roughness has been considerably enhanced and was found to be highest for Relative staggered rib size of 4.

  • thermo hydraulic performance due to Relative Roughness pitch in v down rib with gap in solar air heater duct comparison with similar rib Roughness geometries
    Renewable & Sustainable Energy Reviews, 2015
    Co-Authors: Sukhmeet Singh, Subhash Chander, J. S. Saini
    Abstract:

    Abstract This paper presents thermo-hydraulic performance comparison of rib Roughness under investigation, ‘V-down ribs with gap’ and similar reported rib Roughness geometries used in solar air heater duct. The present rib Roughness has flow-attack-angle and Relative Roughness height of 60° and 0.043, respectively. The duct has aspect ratio of 12 and the Reynolds number ranged from 3000 to 15,000. The roughened wall was uniformly heated while the remaining three walls were insulated. These boundary conditions correspond closely to those found in conventional solar air heaters. Five rib roughened plates having Relative Roughness pitch of 4, 6, 8, 10 and 12 have been tested. The Nusselt number and friction factor were found to be highest for Relative Roughness pitch of 8. Maximum enhancement in Nusselt number and friction factor has been found to be 2.70 and 2.86, respectively. Thermo-hydraulic performance parameter ranged from 1.27 to 1.93. Thermo-hydraulic comparison with similar rib geometries show that the present Roughness geometry performs better for Reynolds number range of 3000–12,000.

Sunil Chamoli - One of the best experts on this subject based on the ideXlab platform.

  • experimental and cfd investigation of convection heat transfer in solar air heater with reverse l shaped ribs
    Solar Energy, 2016
    Co-Authors: Vipin B Gawande, D B Zodpe, A S Dhoble, Sunil Chamoli
    Abstract:

    Abstract A solar air heater is a thermal system which uses artificial Roughness in the form of repeated ribs on the absorber plate to enhance the heat transfer rate. Forced convection heat transfer of air in a solar air heater with reverse L-shaped ribs has been carried out experimentally and numerically. Thermal performance of solar air heater is studied with design variables such as Relative Roughness pitch (7.14 ⩽  P / e  ⩽ 17.86), Reynolds number (3800 ⩽  Re  ⩽ 18,000), heat flux (1000 W/m 2 ) and constant Relative Roughness height ( e / D  = 0.042). A two dimensional CFD simulation is carried out with using CFD code, ANSYS FLUENT and RNG k – ɛ turbulence model, for solving turbulence terms in governing equations. The presence of reverse L-shaped rib shows a significant effect on heat transfer and friction factor characteristics, Relative to change in Relative Roughness pitch ( P / e ) and Reynolds number ( Re ). Thermo hydraulic performance parameter (T.H.P.P) of 1.90 considering heat transfer augmentation with same pumping power, has been evaluated for optimum configuration of the Roughness element (reverse L-shaped rib) for artificially roughened solar air heater. It has been found that the numerical results are in good agreement with the experimental results for the range of parameters investigated. Correlations for Nusselt number and friction factor have been developed as a function of Roughness and flow parameters.

  • a review of cfd methodology used in literature for predicting thermo hydraulic performance of a roughened solar air heater
    Renewable & Sustainable Energy Reviews, 2016
    Co-Authors: Vipin B Gawande, D B Zodpe, A S Dhoble, Sunil Chamoli
    Abstract:

    Abstract A solar air heater is experimentally investigated by many researchers to study the effect of operating and geometrical parameters on heat transfer and fluid flow characteristics. The availability of highly advanced computer hardware and development in numerical methods, encouraging the future researchers to carry out the simulations of solar air heater using various Roughness geometries with different ranges of operating and geometrical parameters. CFD is emerging as an efficient tool to detect the optimum configuration of rib for its maximum thermo hydraulic performance before carrying out actual experimentation. This article discusses different approaches used to investigate the thermal performance of solar air heater. The computational approach, i.e. CFD methodology is discussed using the reference of commercial CFD software ANSYS FLUENT. The main aim of the article is to present a detailed review of the literature that deals with the application of CFD in the design of solar air heater. The paper has a concise summary of each reviewed article in the form of, type of computational domain (2D/3D), turbulence model used, type of CFD commercial software used, range of operating and geometrical parameters and best results obtained from CFD. The article also tabulated the optimum values of Relative Roughness pitch ( P / e ) and Relative Roughness height ( e / D ) for maximum heat transfer enhancement in roughened solar air heater duct.

  • experimental and cfd based thermal performance prediction of solar air heater provided with chamfered square rib as artificial Roughness
    Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2016
    Co-Authors: Vipin B Gawande, D B Zodpe, A S Dhoble, Sunil Chamoli
    Abstract:

    An experimental and two-dimensional computational fluid dynamics (CFD) analysis of a solar air heater has been carried out using chamfered square rib as artificial Roughness on the absorber plate. The Relative Roughness pitch (P/e = 7.14–17.86), chamfer angle (α = 0°–40°), Reynolds number (Re = 3800–18,000) and Relative Roughness height (e/D = 0.042) are chosen as design variables for analysis. A uniform heat flux of 1000 W/m2 is maintained on the surface of absorber plate. CFD code, ANSYS FLUENT 14.5 with renormalization group k-e model was chosen. An enhancement in Nusselt number and friction factor with decrease in Relative Roughness pitch (P/e) is presented and discussed with reference to experimental and CFD analysis. The effect of chamfer angle and Reynolds number on enhancement of Nusselt number and friction factor is also presented. Optimum configuration of Roughness element for artificially roughened solar air heater has been determined in terms of thermo-hydraulic performance parameter. The chamfer angle of 20° on square rib and Relative Roughness pitch of 7.14 provide best thermo-hydraulic performance of 2.047 considering the maximum heat transfer and minimum pressure drop.

  • correlations for solar air heater duct with v shaped perforated baffles as Roughness elements on absorber plate
    International Journal of Sustainable Energy, 2016
    Co-Authors: Sunil Chamoli, N S Thakur
    Abstract:

    An experimental investigation has been carried out to study the effect of heat transfer and friction characteristics of air passing through a rectangular duct which is roughened by V-down perforated baffles. The experiment encompassed Reynolds number (Re) from 3800 to 19,000, Relative Roughness height (e/H) values of 0.285–0.6, Relative Roughness pitch (P/e) range of 1–4 and open area ratio values from 12% to 44%. The effect of Roughness parameters on Nusselt number (Nu) and friction factor (f) has been determined and increase in heat transfer and friction loss has been observed for ducts having a roughened test plate. Maximum Nusselt number is observed for the Relative Roughness pitch ranging from 1.5 to 3 for flow and geometrical parameters under consideration. The experimental data have been used to develop Nusselt number and friction factor correlations as a function of Roughness and flow parameters.

  • ann and rsm approach for modeling and optimization of designing parameters for a v down perforated baffle roughened rectangular channel
    alexandria engineering journal, 2015
    Co-Authors: Sunil Chamoli
    Abstract:

    Abstract The turbulence promoters are widely used to enhance the performance of rectangular channel which were used for turbine blade passage cooling. In the present study, the influence of design parameters of the V down perforated baffle roughened rectangular channel on the heat transfer and friction factor was investigated using RSM and ANN. The quadratic model generated by RSM is used to predict the performance parameters, i.e. Nusselt number and friction factor with reasonably good accuracy. The optimum values of the design parameters of the V down perforated baffle roughened rectangular channel are Relative Roughness pitch of 2.6, Relative Roughness height of 0.33, open area ratio of 18% and Reynolds number of 18,500, in the desirable range of the order of 0.95. The training of the experimental data is carried out using 4-10-2 neural network and the predicted values are compared with the experimental values and found deviation in the range of ±10% among predicted and experimental values. The comparison of predicted values by RSM and ANN with the experimental values was carried out for each run of experiment and it was observed that the RSM predicted values are in accord with the experimental values in the uncertainty range of ±5%.

R P Saini - One of the best experts on this subject based on the ideXlab platform.

  • heat transfer and friction in rectangular solar air heater duct having spherical and inclined rib protrusions as Roughness on absorber plate
    Experimental Heat Transfer, 2019
    Co-Authors: Chandra Prakash, R P Saini
    Abstract:

    ABSTRACTIn this work, an experimental investigation on heat and fluid flow characteristics of artificially roughened solar air heater duct has been carried out. The Roughness and operating parameters covered a range of Reynolds number (Re) from 2000 to 20000, Relative Roughness pitch (P/e) from 15 to 30, Relative rib length (r/g) from 0.4 to 1.0, and Relative rib pitch (Pr/P) from 0.2 to 0.8. Other parameters, i.e., Relative Roughness height (e/D), angle of attack (α), and Relative Roughness gap are kept constant. Results show that the considerable enhancement in Nusselt number and Thermo-hydraulic performance has been obtained with an increase in friction factor using roughened surface.

  • development of correlations for nusselt number and friction factor for solar air heater with roughened duct having multi v shaped with gap rib as artificial Roughness
    Renewable Energy, 2013
    Co-Authors: Anil Kuma, R P Saini, J. S. Saini
    Abstract:

    This paper presents the results of an experimental investigation of heat transfer and friction in the flow of air in rectangular ducts having multi v-shaped rib with gap Roughness on one broad wall. The investigation encompassed Reynolds number (Re) from 2000 to 20,000, Relative gap distance (Gd/Lv) values of 0.24–0.80, Relative gap width (g/e) values of 0.5–1.5, Relative Roughness height (e/D) values of 0.022–0.043, Relative Roughness pitch (P/e) values of 6–12, Relative Roughness width ratio (W/w) values of 1–10, angle of attack (α) range of 30°–75°. The optimum values of geometrical parameters of Roughness have been obtained and discussed. For Nusselt number (Nu), the maximum enhancement of the order of 6.74 times of the corresponding value of the smooth duct has been obtained, however the friction factor (f) has also been seen to increase by 6.37 times of that of the smooth duct. The rib parameters corresponding to maximum increase in Nu and f were Gd/Lv=0.69, g/e=1.0, e/D=0.043, P/e=8, W/w=6 and α=60°. Based on the experimental data, correlations for Nu and f have been developed as function of Roughness parameters of multi v-shaped with gap rib and flow Reynolds number.

  • Experimental investigation on heat transfer and fluid flow characteristics of air flow in a rectangular duct with Multi v-shaped rib with gap Roughness on the heated plate
    Solar Energy, 2012
    Co-Authors: Anil Kumar, R P Saini, J. S. Saini
    Abstract:

    Abstract In this work, results of an experimental investigation of the effect of geometrical parameters of Multi v-shaped ribs with gap on heat transfer and fluid flow characteristics of rectangular duct with heated plate having rib Roughness on its underside have been reported. The range of parameters for this study has been decided on the basis of practical considerations of the system and operating conditions of solar air heaters. The experimental investigation encompassed the Reynolds number (Re) range from 2000 to 20,000, Relative width ratio (W/w) of 6, Relative gap distance (Gd/Lv) of 0.24–0.80, Relative gap width (g/e) of 0.5–1.5, Relative Roughness height (e/D) of 0.043,Relative Roughness pitch (P/e) of 10, angle of attack (α) of 60°. The maximum enhancement in Nusselt number and friction factor is observed to be 6.32–6.12 times of that of the smooth duct, respectively. The thermo-hydraulic performance parameter is found to be the best for the Relative gap distance of 0.69 and the Relative gap width of 1.0.

  • heat transfer and friction factor correlations for a solar air heater duct roughened artificially with multiple v ribs
    Solar Energy, 2010
    Co-Authors: V S Hans, R P Saini, J. S. Saini
    Abstract:

    Abstract The use of artificial Roughness on the underside of the absorber plate is an effective and economic way to improve the thermal performance of a solar air heater. Several experimental investigations, involving different types of Roughness elements, have been carried out to improve the heat transfer from the absorber plate to air flowing in solar air heaters. This paper presents an experimental investigation carried out to study the effect of multiple v-rib Roughness on heat transfer coefficient and friction factor in an artificially roughened solar air heater duct. The experiment encompassed Reynolds number (Re) from 2000 to 20000, Relative Roughness height (e/D) values of 0.019–0.043, Relative Roughness pitch (P/e) range of 6–12, angle of attack (α) range of 30–75° and Relative Roughness width (W/w) range of 1–10. Extensive experimentation has been conducted to collect data on heat transfer and fluid flow characteristics of a rectangular duct roughened with multiple v-ribs. Using these experimental data, correlations for Nusselt number and friction factor in terms of Roughness geometry and flow parameters have been developed.

  • performance prediction of solar air heater having roughened duct provided with transverse and inclined ribs as artificial Roughness
    Renewable Energy, 2009
    Co-Authors: Amar Patnaik, R P Saini, Sunil Kumar Singal
    Abstract:

    Abstract An experimental study has been carried out to investigate the effective efficiency of a solar air heater duct provided with transverse and inclined ribs as artificial Roughness elements on the absorber plate. The range of parameters considered for the present investigation; Reynolds number (Re) 2000–14,000, Relative Roughness pitch (p/e) 3–8 and a fixed value of Relative Roughness height (e/D) of 0.030. The effective efficiency has been computed based on the experimentally determined values for the range of parameters considered. Further an attempt has also been made to optimize the thermal efficiency for the same system under similar conditions by Taguchi method.

V S Hans - One of the best experts on this subject based on the ideXlab platform.

  • investigations on thermo hydraulic performance of broken arc rib in a rectangular duct of solar air heater
    International Communications in Heat and Mass Transfer, 2017
    Co-Authors: R S Gill, V S Hans, Sukhmeet Singh
    Abstract:

    Abstract In present paper, solar air heater duct having aspect ratio 12 roughened with broken arc rib has been investigated. The broken arc is formed by creating symmetrical gap in continuous arc with gap width equal to Roughness height. It has been planned to investigate the influence of position of gap in arc rib on Nusselt number as well as on friction factor. For this purpose, five broken arc rib roughened plates having Relative gap position ranging 0.2–0.8 have been investigated for values of Reynolds number 2000–16000. The remaining Roughness parameters like Relative Roughness height, arc angle, and Relative Roughness pitch were taken as 0.043, 30o and 8 respectively. The presence of broken arc ribs enhanced the Nusselt number, friction factor and thermo-hydraulic performance up to 2.37, 2.55 and 1.94 respectively, compared to smooth duct. The results of ducts roughened with broken arc rib and continuous arc rib have been compared under similar flow conditions. The effect of gap in continuous arc rib on the flow pattern has also been observed using ANSYS Academic Research CFD 15.0.

  • investigation on performance enhancement due to staggered piece in a broken arc rib roughened solar air heater duct
    Renewable Energy, 2017
    Co-Authors: R S Gill, V S Hans, J. S. Saini, Sukhmeet Singh
    Abstract:

    Abstract This paper presents an experimental investigation on heat transfer and friction factor characteristics of solar air heater duct whose absorber is roughened with “broken arc rib combined with staggered rib piece”. The duct has aspect ratio of 12 and the absorber is heated with uniform heat flux while others three walls are insulated. The rib Roughness has fixed Relative staggered rib position, Relative Roughness height, Relative gap size, Relative gap position, arc angle and Relative Roughness pitch of 0.4, 0.043, 1.0, 0.65, 30° and 10 respectively. The Relative staggered rib size and Reynolds number were varied from 1 to 6 and 2000 to 16,000 respectively. The effect of staggered rib on the flow pattern has also been observed using ANSYS Academic Research CFD 15.0. The maximum enhancement in Nusselt number and friction factor over that of broken arc rib roughened duct under similar flow and boundary conditions has been found to be 2.60 and 2.27 times respectively. The corresponding enhancements over that of smooth duct are 3.06 and 2.50 times respectively. The thermo-hydraulic performance of duct roughened with present rib Roughness has been considerably enhanced and was found to be highest for Relative staggered rib size of 4.

  • heat transfer and friction factor correlations for a solar air heater duct roughened artificially with broken arc ribs
    Experimental Thermal and Fluid Science, 2017
    Co-Authors: V S Hans, R S Gill, Sukhmee Singh
    Abstract:

    In present experimental investigation, solar air heater duct with aspect ratio 12 roughened with broken arc rib has been investigated. The broken arc was formed by creating symmetrical gap in continuous arc. To investigate the influence of Roughness parameters of broken arc rib on Nusselt number as well as on friction factor, thirty-seven broken arc rib roughened plates having Relative Roughness pitch (P/e), Relative gap width (g/e), Relative gap position (d/w), Relative Roughness height (e/Dh) and arc angle (α) varying from 4 to 12, 0.5 to 2.5, 0.2 to 0.8, 0.022 to 0.043 and 15° to 75° respectively, have been investigated for Reynolds number range of 2000–16,000. Keeping similar flow conditions, results of broken arc rib roughened duct have been compared with smooth and continuous arc rib roughened ducts. The maximum increase in Nusselt number and friction factor over that of continuous arc rib roughened duct was 1.19 and 1.14 times respectively. The corresponding values over that of smooth duct were 2.63 and 2.44 times respectively. Experimental results of heat transfer and friction in flow have also been correlated in terms of flow and Roughness geometry parameters.

  • heat transfer and friction factor correlations for a solar air heater duct roughened artificially with multiple v ribs
    Solar Energy, 2010
    Co-Authors: V S Hans, R P Saini, J. S. Saini
    Abstract:

    Abstract The use of artificial Roughness on the underside of the absorber plate is an effective and economic way to improve the thermal performance of a solar air heater. Several experimental investigations, involving different types of Roughness elements, have been carried out to improve the heat transfer from the absorber plate to air flowing in solar air heaters. This paper presents an experimental investigation carried out to study the effect of multiple v-rib Roughness on heat transfer coefficient and friction factor in an artificially roughened solar air heater duct. The experiment encompassed Reynolds number (Re) from 2000 to 20000, Relative Roughness height (e/D) values of 0.019–0.043, Relative Roughness pitch (P/e) range of 6–12, angle of attack (α) range of 30–75° and Relative Roughness width (W/w) range of 1–10. Extensive experimentation has been conducted to collect data on heat transfer and fluid flow characteristics of a rectangular duct roughened with multiple v-ribs. Using these experimental data, correlations for Nusselt number and friction factor in terms of Roughness geometry and flow parameters have been developed.