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.

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.

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.

scholarly journals Thermal Performance of Three Sided Artificially Roughened Double Duct Parallel Flow Solar Air Heater

2018 ◽  
Vol 7 (1) ◽  
pp. 5-15
Author(s):  
Chander Kant ◽  
Prashant Kumar ◽  
Ankur Gill ◽  
Dhiraj Parkash Dhiman
Keyword(s):  
Heat Transfer ◽  
Reynold Number ◽  
Parallel Flow ◽  
Working Fluid ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Air Heater ◽  
Relative Roughness

A solar air heater is basically a heat exchanger, which intercepts the incident solar radiation, converts it into heat and finally transfers this heat to a working fluid for an end use system. The mode of air flowing in the ducts of a solar air heater is one of the most significant aspects concerned with solar air heater which dominantly affect. A double duct parallel flow artificially roughened solar air heater with three sides of the absorber plate is investigated in the current study. Unlike the conventional model of solar air heater with only one sided roughened absorber plate, a novel solar air heater with three artificially roughened absorber plate is used so that the surface area of the absorber plate is increased which ultimately increases the rate of heat transfer. Additionally, a double duct parallel flow arrangement through inner and outer duct of solar air heater is considered order to enhance the heat transfer rate. A numerical investigation of the heat transfer and friction factor characteristics of a double duct parallel flow three sided artificially roughened solar air heater has been carried out. A commercial finite volume CFD code ANSYS FLUENT is used to simulate turbulent air flow through artificial roughened solar air heater. Governing equations of the fluid flow and heat transfer i.e. Navier-Stokes equation and energy equation are solved with RNG k-ε turbulence model. Nine different configuration of square rib are studied with relative roughness pitch (P/e = 5-10) and relative roughness height (e/D = 0.03-0.06). The Reynold number of the flow is varied from 2500 to 16000.

Heat Transfer and Friction Factor Correlations for Solar Air Heater With Gap in V-Rib With Symmetrical Gap and Staggered Ribs

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Sumer Singh Patel ◽  
Atul Lanjewar
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Smooth Surface ◽  
Heat Transfer Analysis ◽  
Operating Parameters ◽  
Solar Air Heater ◽  
Gap Size ◽  
Maximum Enhancement ◽  
Air Heater ◽  
Relative Roughness

Abstract The present experimental study is concerned with heat transfer analysis of air flowing in solar air heater duct with a gap in V-rib with symmetrical gap and staggered ribs geometry. The investigated parameters are Reynolds number (Re) of 4000–14,000, relative roughness pitch (p/e) of 12, relative roughness height (e/Dh) of 0.043, angle of attack (α) of 60 deg, relative staggered rib pitch (p′/p) of 0.65, relative gap size (g/e) of 4, relative staggered rib size (r/e) of 4, relative gap position of additional gap in each symmetrical rib elements (d/w) of 0.65, relative gap size of additional gap in each symmetrical rib elements (g′/e) of 1, number of main gaps (Ng) of 1, 2, 3, 4, and number of additional gap (ng) varying from 1 to 5. Fourteen roughened absorber plates were tested. The maximum enhancement in Nusselt number (Nu) and friction factor (f) was 2.34 and 2.79 times that of smooth surface corresponding to the number of main gaps (Ng) of 4 with the number of additional gaps (ng) of 4. The performance of the gap in V-rib with symmetrical gap and staggered rib geometry has been compared with the existing latest V-rib geometry and smooth surface. The proposed gap in V-rib with symmetrical gap and staggered ribs geometry has a better performance than the existing latest V-rib geometry. The following correlations have been developed for heat transfer and friction factor in terms of roughness and operating parameters. Heat transfer:Nur=0.0073(Re)0.9788(Ng)0.2790(ng)0.0184exp[−0.1678(ln(Ng))2]exp[−0.0129(ln(ng))2] Friction factor:fr=0.0477(Re)−0.0678(Ng)0.5919(ng)−0.0562exp[−0.4922(ln(Ng))2]exp[−0.0487(ln(ng))2]

scholarly journals Modeling and Simulation of Turbulent Flows through a Solar Air Heater Having Square-Sectioned Transverse Rib Roughness on the Absorber Plate

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Anil Singh Yadav ◽  
J. L. Bhagoria
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Convective Heat Transfer Coefficient ◽  
Performance Parameter ◽  
Roughness Height ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Air Heater ◽  
Relative Roughness ◽  
Flow Through

Solar air heater is a type of heat exchanger which transforms solar radiation into heat energy. The thermal performance of conventional solar air heater has been found to be poor because of the low convective heat transfer coefficient from the absorber plate to the air. Use of artificial roughness on a surface is an effective technique to enhance the rate of heat transfer. A CFD-based investigation of turbulent flow through a solar air heater roughened with square-sectioned transverse rib roughness has been performed. Three different values of rib-pitch (P) and rib-height (e) have been taken such that the relative roughness pitch (P/e=14.29) remains constant. The relative roughness height,e/D, varies from 0.021 to 0.06, and the Reynolds number, Re, varies from 3800 to 18,000. The results predicted by CFD show that the average heat transfer, average flow friction, and thermohydraulic performance parameter are strongly dependent on the relative roughness height. A maximum value of thermohydraulic performance parameter has been found to be 1.8 for the range of parameters investigated. Comparisons with previously published work have been performed and found to be in excellent agreement.

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.

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