On the Use of Longitudinal Fins to Enhance the Performance in Rectangular Duct of Solar Air Heaters—A Review

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Mukesh Kumar Sahu ◽  
Manoj Sharma ◽  
M. M. Matheswaran ◽  
Kinshuk Maitra
Keyword(s):  
Heat Transfer ◽  
Present Article ◽  
Thermal Performance ◽  
Bottom Plate ◽  
Operating Parameters ◽  
Solar Air Heater ◽  
Rectangular Duct ◽  
Detailed Review ◽  
Extended Surface ◽  
Different Shapes

The objective of the present article is to present a detailed review of the research carried out on the use of extended surface in the form of longitudinal fins, with its different shapes, geometries, and attachments on solar air heater (SAH), to improve the thermal performance of conventional SAH duct. The use of extended surface in the scheme of fins placed longitudinally along the air-flow path on the absorber or bottom plate surfaces is an effective method to augment the performance of SAH duct. Various studies have been carried out through employing longitudinal fins for the enhancement in thermal performance of simple SAH duct. Finally, all the details of the literature as a summary, i.e., about fin geometries, systems, and operating parameters for analysis, are compiled together and well tabulated. The investigators used correlations for heat transfer, and friction factor also has been classified and presented in a relevant form in the present article. Finally, an attempt has been made to compare the performances of different finned SAHs by using correlations.

scholarly journals Augmentation of Heat Transfer in a Circular Channel with Inline and Staggered Baffles

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8593
Author(s):  
Muneerah Al Nuwairan ◽  
Basma Souayeh
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Working Fluid ◽  
Solar Air Heater ◽  
Circular Channel ◽  
Maximum Enhancement ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Sst Model ◽  
Inlet Length

This numerical investigation presents the effects of the position of baffles in the shape of a circle’s segment placed inside a circular channel to improve the thermal and flow performance of a solar air heater. Three different baffles’ positions with Reynolds number varying between 10,000 to 50,000 were investigated computationally. The k-omega SST model was used for solving the governing equations. Air was taken as the working fluid. Three pitch ratios (Y = 3, 4, and 5) were considered, while the height of the baffles remained fixed. The result showed an enhancement in Nusselt number, friction factor, j-factor, and thermal performance factor. Staggered exit-length baffles showed maximum enhancement in heat transfer and pressure drop, while inline inlet-length baffles showed the least enhancement. For a pitch ratio of Y = 3.0, the enhancement in all parameters was the highest, while for Y = 5.0, the enhancement in all parameters was the least. The highest thermal performance factor of 1.6 was found for SEL at Y = 3.0.

scholarly journals Experimental Studies on a Solar Air Heater Having V-Corrugated Absorber Plate with Obstacles Bent Vertically

2014 ◽  
Vol 493 ◽  
pp. 86-92 ◽  
Author(s):  
Ekadewi A. Handoyo ◽  
Djatmiko Ichsani ◽  
Prabowo ◽  
S. Sutardi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flat Plate ◽  
Air Temperature ◽  
Temperature Rise ◽  
Experimental Studies ◽  
Bottom Plate ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Air Heater

A solar air heater (SAH) is a simple heater using solar radiation that is useful for drying or space heating. Unfortunately, heat transfer from the absorber plate to the air inside the solar air heater is low. Some researchers reported that obstacles are able to improve the heat transfer in a flat plate solar air collector and others found that a v-corrugated absorber plate gives better heat transfer than a flat plate. Yet, no work of combining these two findings is found.This paper describes the result of experimental study on a SAH with v-corrugated absorber plate and obstacles bent vertically started from 80oto 0owith interval 10oon its bottom plate. Experiments were conducted indoor at five different Reynolds numbers (1447 Re 7237) and three different radiation intensities (430, 573, and 716 W/m2).It is found that the obstacles improve SAH performance. Both the air temperature rise and efficiency increase with inserting obstacles bent at any angle vertically. Unfortunately, the air pressure drop is increasing, too. Obstacles bent vertically at smaller angle (means more straight) give higher air temperature rise and efficiency. However, the optimum angle is found 30o. The air temperature rise and efficiency will be 5.3% lower when the obstacles bent 30oinstead of 0o, but the pressure drop will be 17.2% lower.

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]

Heat Transfer Augmentation From Extended Surface Using Dimples

2018 ◽  
Author(s):  
Jay D. Mehta ◽  
Fay N. Colah ◽  
Anurag P. Rao ◽  
Vineeta P. Pendse ◽  
Vyankatesh U. Bagal ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Surface Modifications ◽  
Exposed Surface ◽  
Transfer Rates ◽  
Heat Transfer Augmentation ◽  
Extended Surface ◽  
Extended Surfaces ◽  
Exposed Surface Area

This paper concentrates on comparing dimples to improve the heat transfer rate from extended surfaces under forced convection conditions. Dimples are milled on the surface of the fins while keeping the exposed surface area between the various designs as constant. Spherical dimples, ellipsoidal dimples, cylindrical dimples, and pyramidal dimples are selected as part of the paper. Experimental results are compared with results obtained from simulation. The paper concludes that surface modifications improve the heat transfer rates. The paper also compares the thermal performance of various shapes of dimples.

Using Porous Fins for Heat Transfer Enhancement

2000 ◽  
Vol 123 (4) ◽  
pp. 790-795 ◽  
Author(s):  
S. Kiwan ◽  
M. A. Al-Nimr
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Performance ◽  
Thermal Conductivity Ratio ◽  
Operating Parameters ◽  
Conductivity Ratio ◽  
Transfer Enhancement ◽  
Porous Fin ◽  
Novel Method ◽  
Porous Fins

This work introduces a novel method that enhances the heat transfer from a given surface by using porous fins. The thermal performance of porous fins is estimated and compared with that of the conventional solid fins. It is found that using porous fin of porosity ε may enhance the performance of an equal size conventional solid fin and, as a result, save 100 ε percent of the fin material. The effect of different design and operating parameters on the porous fin thermal performance is investigated. Examples of these parameters are Ra number, Da number, and thermal conductivity ratio. It is found that more enhancement in the porous fin performance may be achieved as Ra increases especially at large Da numbers. Also, it is found that there is an optimum limit for the thermal conductivity ratio beyond which there is no further improvement in the fin performance.

scholarly journals Solar Air Heater with W-Shaped Roughness on Absorber Plate

2019 ◽  
Vol 8 (9) ◽  
pp. 2218-2222
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Heat Input ◽  
Solar Irradiance ◽  
Smooth Surface ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Roughened Surface

The analysis is made for Reynolds number of 18000 – 21000. The thermal performance is investigated for W – shaped roughness of thickness (t) 5mm, length of 10.5 cm, with an angle of 25°. The simulation is carried out using solar irradiance as heat input at the location of Amravati 20.93°N 77.75°E. Comparison of Reynolds no and Nusselt no is made. The thermal efficiency is found to increase as the temperature goes on increasing simultaneously the pressure at outlet is greater than inlet pressure. The mechanical power which is required is increased due to the roughness present on absorber plate. The heat transfer between smooth and roughened surface is compared. The experimental results are compared with analytical results on ANSYS 18.1. The thermal efficiency for the smooth surface is around 40 – 45% at particular temperature after roughening the absorber plate the efficiency increased upto 50 – 60% for the same temperature.

Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

1996 ◽  
Author(s):  
Tong-Miin Liou ◽  
Woei-Jiunn Shuy ◽  
Yu-Houe Tsao
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Pressure Measurements ◽  
Rectangular Duct ◽  
Height Ratio ◽  
Heat Transfer Augmentation ◽  
Spatially Periodic ◽  
The Difference

Laser holographic interferometry and pressure measurements are presented for the effects of rib-to-duct height ratio (H/2B), rib pitch-to-height ratio (Pi/H), and Reynolds number (Re) on the spatially periodic-fully developed turbulent heat transfer and friction in a rectangular duct of width-to-height ratio of 4:1 with an array of ribs detached from one wall at a clearance to rib-height ratio of 0.38. The range of H/2B, Pi/H, and Re examined were 0.13 to 0.26, 7 to 13, and 5×103 to 5×104, respectively. The difference in the H/2B dependence of the thermal performance between the detached and attached solid-rib array is documented. H/2B=0.17 and Pi/H=10 are found to provide the best thermal performance for the range of parameters tested. Compact heat transfer and friction correlations are developed. Additionally, it is found that heat transfer augmentation with a detached solid-rib array is superior to with a detached perforated-rib array, and the mechanism responsible for the difference is revealed by the complementary flow visualization results.

scholarly journals Optimizing Thermal Efficiencies of Double-Pass Cross-Corrugated Solar Air Heaters on Various Configurations with External Recycling

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4019
Author(s):  
Chii-Dong Ho ◽  
Hsuan Chang ◽  
Ching-Fang Hsiao ◽  
Yu-Chen Lin
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Operating Conditions ◽  
Transfer Efficiency ◽  
Bottom Plate ◽  
Device Performance ◽  
Absorber Plate ◽  
Double Pass ◽  
Operational Conditions ◽  
Heat Transfer Efficiency

The effect of external-recycle operations on the thermal performance of double-pass cross-corrugated solar air heaters (SAH) under different operating conditions was investigated experimentally and theoretically. Additionally, the simultaneous ordinary equations were solved analytically for each proposed configuration. Four recycling types are introduced for improving the solar thermal performance with different external recycle processes, which are expected to enhance the heat transfer coefficient with a convective turbulent flow between the air and the absorber in the present study. Using recycling double-pass operations, two processes were conducted sequentially: air first flowed over the sinusoidal corrugated absorber plate and then flowed back later over the transverse sinusoidal corrugated bottom plate. Improved device performance was achieved due to the doubled heat transfer area over and under the corrugated absorber plate, from which both the sinusoidal cross-corrugated absorber plate and bottom plate enhanced turbulent intensity. Theoretical predictions and experimental results both indicated that the recycle ratio increased with the SAH thermal efficiency for all proposed designs. The results show a higher heat transfer efficiency for the proposed four configurations using wavelike corrugated plates compared to those conducted in single-pass and flat-plate absorber plates with up to a maximum 133% (from 0.301 to 0.703) increment. The optimal device performance was examined for all external-recycle configurations under the same working dimensions and operational conditions. The best configuration for optimal thermal performance was the device that lengthened the air flow pathway and increased the air velocity within the collector; thus, a higher heat transfer rate was accomplished. The evaluation of increments in the power consumption and of the heat-transfer efficiency enhancement together determined the optimal design based on an economic consideration across various configurations of cross-corrugated double-pass devices.

scholarly journals EFFECT OF ARTIFICIAL ROUGHNESS ON HEAT TRANSFER AND FRICTION CHARACTERSTICS OF DOUBLE PASS SOLAR AIR HEATER

2013 ◽  
pp. 52-56
Author(s):  
AVDHESH SHARMA ◽  
VARUN VARUN ◽  
GAURAV BHARADWAJ
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Solar Air Heater ◽  
Rectangular Duct ◽  
Artificial Roughness ◽  
Absorber Plate ◽  
Double Pass ◽  
Air Heater ◽  
Aluminium Wire

Double pass solar air heater (DPSAH) consisted of rectangular duct provided with artificial roughness on both side of the absorber plate has been experimentally investigated. Circular ribs of aluminium wire is used to provide roughness to increase heat transfer coefficient between absorber plate and air. Ribs are attached to absorber plate at four different angle of attackbetween 30° to 75° . Experiment is carried out over the range of Reynolds Number from 4900 to 12000, and relative roughness height (e/Dh) varies from 0.022 to 0.044. Experimentally different values of Nusselt number(Nu). and friction factor(fr) have been determined for various parameters. The enhance-ment in heat transfer and increment in the friction factor values of Nusselt number and friction factor have also been compared with the smooth one.

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