Three-Dimensional Thermo-Hydraulic Analysis of Solar Air Heater With Equilateral Prism-Shaped Rib Roughness

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Inzamam Ahmad ◽  
N. H. Khan ◽  
M. A. Hassan ◽  
M. K. Paswan
Keyword(s):  
Nusselt Number ◽  
Friction Factor ◽  
Average Nusselt Number ◽  
Three Dimensional ◽  
Hydraulic Performance ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Flow Friction ◽  
Air Heater ◽  
Relative Roughness

Abstract Thermal transport and flow friction characteristics due to roughness on the absorber plate of solar air heater are evaluated by applying three-dimensional finite volume based code. Renormalization group (RNG) k–ɛ model is employed to capture the turbulent nature of the flow. The effect of equilateral prism-shaped rib roughness geometrical parameters in terms of relative roughness height (e/D) and relative roughness pitch (p/e) on heat transfer and flow friction is analyzed. Further, the effect of flow parameter, Re in the range of 4000–18,000 is also explored. Results are elucidated in terms of average Nusselt number, friction factor, turbulent kinetic energy, and eddy dissipation. Results are compared with a smooth absorber plate solar air heater. Thermo-hydraulic performance of the roughened solar air heater is analyzed. Noteworthy augmentation in heat transport is obtained. The thermal enhancement factor is calculated for optimal performance and found to vary from 1.7 to 3.5. However, friction factor and pressure loss for roughened plate is significantly higher than its smooth counterpart. The pressure drop across the test section increases with the rise in roughness height due to flow obstruction. A minimum value of the friction factor enhancement ratio worth 2.13 is obtained. Enhancement in thermal transport and pressure losses are combined by introducing a thermo-hydraulic performance factor (THHP). For the range of parameters investigated, the optimum value of the thermo-hydraulic performance factor is found to be 3.41. Correlations for average Nusselt number and friction factor are offered at the end.

Thermal–hydraulic analysis of a solar air heater fitted with a wire-roughened absorber plate

2021 ◽  
pp. 095440892110590
Author(s):  
Nanjundappa Madhukeshwara ◽  
A Alhadhrami ◽  
Hassan A H Alzahrani ◽  
B H Prasanna
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Efficiency Index ◽  
Hydraulic Performance ◽  
Index Formula ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Air Heater ◽  
Relative Roughness ◽  
Nusselt Numbers

This study is to evaluate heat transmission and friction in a rectangular solar air heater with a V-shaped wire rib roughness on the absorber plate that operates in fully formed turbulent flow. Additionally, studies are performed to generate prediction equations for the average friction factor, Stanton number, and efficiency index. The Reynolds number [Formula: see text]–[Formula: see text], angle of attack [Formula: see text]20[Formula: see text]–90[Formula: see text]), relative roughness pitch [Formula: see text]–[Formula: see text], relative roughness height [Formula: see text]–[Formula: see text], and the aspect ratio [Formula: see text]–[Formula: see text] was varied. The efficiency index [Formula: see text] is commonly employed as a thermo-hydraulic performance metric. It is computed as [Formula: see text]. The wire roughness and airflow parameters [Formula: see text] are optimized to maximize heat transfer while retaining minimal friction losses. On the basis of resemblance criteria, average Stanton numbers, average Nusselt numbers, and even average friction factors are derived. The results are compared to those obtained with a smooth absorber duct under similar airflow circumstances in order to assess the increase in heat transfer coefficient and friction factor. The [Formula: see text], and [Formula: see text] have a significant influence on thermo–hydraulic performance, according to these studies. With [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], the optimal configuration geometry for wire roughness and solar air heater duct is identified.

scholarly journals CFD Analysis to Study Effect of Circular Vortex Generator Placed in Inlet Section to Investigate Heat Transfer Aspects of Solar Air Heater

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Vipin B. Gawande ◽  
A. S. Dhoble ◽  
D. B. Zodpe
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Vortex Generator ◽  
Inlet Section ◽  
Solar Air Heater ◽  
Cfd Analysis ◽  
Absorber Plate ◽  
Air Heater ◽  
Relative Roughness

CFD analysis of 2-dimensional artificially roughened solar air heater duct with additional circular vortex generator, inserted in inlet section is carried out. Circular transverse ribs on the absorber plate are placed as usual. The analysis is done to investigate the effect of inserting additional vortex generator on the heat transfer and flow friction characteristics inside the solar air heater duct. This investigation covers relative roughness pitch in the range of 10 ≤P/e≤ 25 and relevant Reynolds numbers in the range of 3800 ≤ Re ≤ 18000. Relative roughness height (e/D) is kept constant as 0.03 for analysis. The turbulence created due to additional circular vortex generator increases the heat transfer rate and at the same time there is also increase in friction factor values. For combined arrangement of ribs and vortex generator, maximum Nusselt number is found to be 2.05 times that of the smooth duct. The enhancement in Nusselt number with ribs and additional vortex generator is found to be 1.06 times that of duct using ribs alone. The maximum increase in friction factor with ribs and circular vortex generator is found to be 2.91 times that of the smooth duct. Friction factor in a combined arrangement is 1.114 times that in a duct with ribs alone on the absorber plate. The augmentation in Thermal Enhancement Factor (TEF) with vortex generator in inlet section is found to be 1.06 times more than with circular ribs alone on the absorber plate.

scholarly journals Effect of rib roughness pitch on thermal and thermo-hydraulic performance of a solar air heater roughened artificially with arc rib having gap

2016 ◽  
Vol 8 (1) ◽  
pp. 251-256
Author(s):  
V. S. Hans ◽  
R. S. Gill ◽  
Rupinderpal Singh
Keyword(s):  
Hydraulic Performance ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Degree Relative ◽  
Number Range ◽  
Air Heater ◽  
Relative Roughness ◽  
Flow Reynolds Number ◽  
Gap Width ◽  
Rib Roughened

This experimental study on a solar air heater having absorber plate roughened artificially by providing roughness in the form of arc ribs having gap was carried out in the Department of Mechanical Engineering, Punjab Agricultural University, Ludhiana, India to study the effect of relative roughness pitch on thermal and thermohydraulic performance as well as to compare the performance of arc rib with gap roughened solar air heater with that of continuous arc rib roughened solar air heater. The roughness geometry parameters included relative roughness height of 0.043, angle of attack of 30 degree, relative gap position of 0.80, gap-width equal to the width of the rib and five values of relative roughness pitch ranging from 4 to 12 for flow Reynolds number range of 2000 to 16,000. The Nusselt number and friction factor were found to be more for relative roughness pitch value of 10 as compared to other values of relative roughness pitch. Thermo-hydraulic performance of solar air heaters roughened by arc with gap and continuous arc roughness geometries were found to be 1.91 times and 1.78 times respectively as compared to that of solar air heater having smooth absorber plate due to generation of turbulence in laminar sublayer region. However, improvement in thermo-hydraulic performance of solar air heater roughened by arc with gap geometry over continuous arc rib roughened solar air heater was attributed to generation of a region of turbulence on downstream side of the gap.

Heat Transfer Augmentation Using an Innovative Helicoidal Finned Absorber Plate in a Solar Air Heater—A Numerical Study

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Shantanu Purohit ◽  
N. Madhwesh ◽  
K. Vasudeva Karanth ◽  
N. Yagnesh Sharma
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Diameter Ratio ◽  
Wire Diameter ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Air Heater ◽  
Pitch Ratio

This study presents an innovative idea to augment heat transfer to an air heater using helicoidal finned arrangement. A parametric analysis of the helicoidal shaped fin geometry is considered with helicoidal pitch ratio of 0.1666–0.3, fin diameter ratio of 1.75–2. For the placement of the fin beneath the absorber plate, longitudinal pitch ratio ranging from 0.0416 to 0.1666 are used. The flow Reynolds number used for the study ranges from 4800 to 25,000. The effects of helicoidal pitch ratio, wire diameter ratio and longitudinal pitch ratio on Nusselt number and friction factor have been discussed. It is seen from the analysis that there is a significant improvement in Nusselt number for the case of helicoidal fin of wire diameter ratio of 1 when compared to base model as well as straight fin model for the operating range of Reynolds number. It is also observed from the analysis that for the helicoidal fin configuration of helicoidal pitch ratio of 0.2333, friction factor appears to be moderate. Flow and roughness parameters for roughened solar air heater have been optimized using thermal-hydraulic enhancement factor (THEF). The study reveals that by the use of helicoidal fins, maximum enhancement in the Nusselt number is found to be 2.21 times when compared to the base model for longitudinal pitch ratio of 0.0416, helicoidal pitch ratio of 0.166 for a fixed wire diameter. The improvement obtained in performance corresponding to increased Nusselt number establishes the efficacy the helicoidal fin design for the absorber plate.

scholarly journals Nusselt Number and Friction Factor Correlations Development for Arc-Shape Apex Upstream Artificial Roughness in Solar Air Heater

2021 ◽  
Author(s):  
Mukesh Kumar Sahu ◽  
Manjeet Kharub ◽  
Mahalingam Murugesan Matheswaran
Keyword(s):  
Nusselt Number ◽  
Friction Factor ◽  
Roughness Element ◽  
Circular Cross Section ◽  
Solar Air Heater ◽  
Enhancement Ratio ◽  
Air Heater ◽  
Relative Roughness ◽  
Evaluation Of Performance ◽  
Arc Shape

Abstract In the present work an outdoor experimental investigation for solar air heater with arc-shaped apex-upstream flow by the use of circular cross section wires as roughness elements has been carried out. The roughness-element have been expressed in non-dimensionalizing geometric parameters as relative roughness-pitch (P/e), relative roughness-height (e/D) and flow attack-angle (α/60), and the range of these parameters varies from 8 to 15, 0.0454, and 0.75 to 1.25, respectively. For evaluation of performance of the roughened SAH, a novel parameter has been proposed and introduced in the present investigation which is Thermo-Hydraulic Improvement Parameter (THIP). With the use of present roughness geometry, considerably Nusselt number enhancement ratio (NNER) and friction factor enhancement ratio (FFER) have been observed. The maximum NNER and FFER values obtained experimentally is about 2.83 and 1.79 times, respectively. While, the maximum THIP has been obtained 157.49% higher than the smooth SAH. Using the experimental results correlations for the output parameters (Nusselt number and friction factor) as a function of input parameters (flow and roughness) have been developed.

Experimental Investigation of Thermohydraulic Performance of the Solar Air Heater Having Arc-Shaped Ribs With Multiple Gaps

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Sheetal Kumar Jain ◽  
Ghanshyam Das Agrawal ◽  
Rohit Misra
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Nusselt Number ◽  
Friction Factor ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Absorber Plate ◽  
Maximum Enhancement ◽  
Air Heater ◽  
Absorber Surface

Abstract In the present research, the thermohydraulic performance of a solar air heater having artificial roughness in the form of arc-shaped ribs with multiple gaps has been investigated experimentally and compared with that of a solar air heater having smooth absorber plate. The performance has been investigated in terms of enhancement in the Nusselt number and friction factor. Results of the present work have also been compared with previously published work. Reynolds number and arc angle (α) were varied from 3000 to 18,000 and 30 deg to 75 deg, respectively. Present roughness results in a higher rate of heat transfer from the absorber surface to air, but it also imposes a penalty in terms of the increased friction factor. Maximum enhancement in Nusselt number, friction factor, and thermohydraulic performance parameter for the roughened absorber surface is found to be 3.74, 2.69, and 2.75 times that of the smooth plate, respectively. Correlations of heat transfer and friction factor for proposed roughness have also been developed.

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