Investigation on influence of dimpled surfaces on heat transfer enhancement and friction factor in solar water heater

Manoram, R.B.; Moorthy, R. Sathiya; Ragunathan, R.

doi:10.1007/s10973-020-09746-0

Cited by 32 publications

(7 citation statements)

References 41 publications

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“…When non-uniformly heated air from the collector is utilized for process applications, such as drying of food materials, it may lead to inefficient drying and poor food quality. Previous studies also emphasized the limitations of FPSC and presented the need for its performance improvement [19,24,40]. Considering the listed limitations of FPSC, smooth absorber plate was modified with the introduction of baffles/diversion and semicircular loops in order to generate better turbulence and disturb thermal boundary layer, with the aim of obtaining higher heat transfer in conjunction with uniform temperature distribution at collector outlet.…”

Section: Air Temperature-velocity Profile Inside the Fpscmentioning

confidence: 99%

“…Singh et al [20] observed 2.50 times gain in heat transfer along with 3.29 times expansion in pumping power of air in square wave shaped ribs, while multiple broken ribs provided 3. 24 times enhanced heat transfer and 3.85 times increase in pumping power. A study carried out by Saravankumar et al [21] revealed that artificially roughened absorber plate integrated with fins and baffled collector experienced 27.1% enhanced effective efficiency as compared to roughened solar air collector.…”

Section: Introductionmentioning

confidence: 99%

“…Sivakumar et al [23] found 17 °C higher outlet air temperature, 12% higher thermal efficiency along with 60% increase in pressure drop in pin-fin collector as compared to conventional FPSC. Manoram et al [24] reported the significant effect of pitchto-diameter ratio and the number of dimples on the thermal efficiency and friction factor of solar water heating system. Further, Sudhakar and Cheralathan [25] presented a double pass solar collector with V-grove absorber plate with and without pin-fins for application in agricultural products drying.…”

Section: Introductionmentioning

confidence: 99%

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Heat transfer augmentation of flat plate solar collector through finite element-based parametric study

Rani

Tripathy

2020

J Therm Anal Calorim

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The introduction of fins and baffles on the absorber plate is an effective way to ameliorate the thermal performance of flat plate solar collector (FPSC), but obstructs the air passage leading to considerable pumping power penalty. In the current work, attempt is made to improve the overall performance of collector with the incorporation of hollow semicircular loop fins and rectangular baffles over the absorber plate for air mass flow rate ranging from 0.006 to 0.02 kg s −1 . A parametric study was carried out with finite element approach considering different radius (2-4 cm), pitch (6-20 cm) and number of semicircular loops per row in transverse direction (3-8 loops). Compared to intermittent loops, placement of continuous staggered semicircular loops was more effective for attaining uniform profile and higher magnitude of air temperature at collector outlet. With regard to FPSC, finned collector provided 2.64-2.95 times greater Nusselt number and 41-75% higher thermal efficiency, as well as exhibited 8.38-10.4 K higher collector outlet average air temperature. The pressure drop noted for FPSC was 0.14 Pa and increased to the range of 0.5-0.7 Pa with the addition of loops and baffles at an air mass flow rate of 0.01 kg s −1 . Collector having baffles and continuous semicircular loops of radius 3 cm, made up of 2-mm-thick wire, presented maximum thermohydraulic performance factor of 1.73 in conjunction with showing maximum magnitude and uniform profile of collector outlet temperature. The modified collector with semicircular loops along with baffles will find its application in efficient drying of agricultural commodities.

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Section: Air Temperature-velocity Profile Inside the Fpscmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heat transfer augmentation of flat plate solar collector through finite element-based parametric study

Rani

Tripathy

2020

J Therm Anal Calorim

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“…At a low Reynolds number (=2000), the thermal performance of the tube can be improved by 150%. The effect of the 3D cavity in solar water heating application is investigated by Manoram et al (2021) and they noticed a 250% increase in thermal performance with only an 11.1% increase in hydraulic loss when the pitch to diameter ratio is kept 3. The four different dimpled cavities were investigated in a square duct by Xie et al (2013) and analyzed the flow structure along with heat transfer through it.…”

Section: Introductionmentioning

confidence: 99%

Application of triangular duct in solar assisted air-heating system with surface roughness: A numerical investigation

Kumar

Re²,

Kharub³

et al. 2023

Preprint

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A solar air heater is a simple device designed to collect solar radiation for air heating purpose and the heated air can further be used for space heating, drying, etc. The conventional air heater (solar assisted) has poor performance and with this work an attempt has been made to improve its performance by providing surface roughness over the heated surface. The roughness employed over the surface has elliptical cavity and its dimensions and placement over the heated surface is defined with the dimensionless parameters (relative cavity depth; Dd, relative crosswise distance; Dc, and relative flow-wise distance; Df which varied from 0.016 to 0.038, 6-14, and 6 to 14, respectively). A CFD code has been development and validated with the experimental results to do the parametric analysis for understand the effect of proposed surface roughness on the performance of air-heater. It is concluded that the proposed surface roughness promotes the local turbulence, flow separation, and strong vortices in the flow-field with resulted comparatively higher thermal performance in the proposed air-heater. But, this higher thermal performance achieved at the expense of higher pressure loss in the passage. The augmentation of heat increases substantially by 2.57 times at the expanse of 2.3 times increase in pressure at relative cavity depth (Dd); relative crosswise distance (Ds); and relative flow-wise distance (Dl) of 0.038, 10, and 10, respectively. However, the overall performance is 1.75 times higher in the proposed air-heater in comparison to the conventional designs.

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“…It has been found that the dimple depth-diameter ratio plays an important role in flow and heat transfer characteristics near the dimple. However, many current studies in dimpled channels mainly focus on the heat transfer of simple fluid such as water [19][20][21]. Those results cannot be simply migrated to structural optimizations of dimples in the unilateral-heated cooling channels of hydrocarbon-fueled scramjet engines.…”

Section: Introductionmentioning

confidence: 99%

Effect of Dimple Depth-Diameter Ratio on the Flow and Heat Transfer Characteristics of Supercritical Hydrocarbon Fuel in Regenerative Cooling Channel

Qin

et al. 2021

International Journal of Aerospace Engineering

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In order to extend the cooling capacity of thermal protection in various advanced propulsion systems, dimple as an effective heat transfer enhancement device with low-pressure loss has been proposed in regenerative cooling channels of a scramjet. In this paper, numerical simulation is conducted to investigate the effect of the dimple depth-diameter ratio on the flow and heat transfer characteristics of supercritical hydrocarbon fuel inside the cooling channel. The thermal performance factor is adopted to evaluate the local synthetically heat transfer. The results show that increasing the dimple depth-diameter ratio h / d p can significantly reduce wall temperature and enhance the heat transfer inside the cooling channel but simultaneously increase pressure loss. The reason is that when h / d p is rising, the recirculation zones inside dimples would be enlarged and the reattachment point is moving downstream, which enlarge both the high Nu area at rear edge of dimple and the low Nu area in dimple front. In addition, when fluid temperature is nearer the fluid pseudocritical temperature, local acceleration caused by dramatic fluid property change would reduce the increment of heat transfer and also reduce pressure loss. In this study, the optimal depth-diameter ratio of dimple in regenerative cooling channel of hydrocarbon fueled is 0.2.

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Investigation on influence of dimpled surfaces on heat transfer enhancement and friction factor in solar water heater

Cited by 32 publications

References 41 publications

Heat transfer augmentation of flat plate solar collector through finite element-based parametric study

Heat transfer augmentation of flat plate solar collector through finite element-based parametric study

Application of triangular duct in solar assisted air-heating system with surface roughness: A numerical investigation

Effect of Dimple Depth-Diameter Ratio on the Flow and Heat Transfer Characteristics of Supercritical Hydrocarbon Fuel in Regenerative Cooling Channel

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