Device Performance Improvement of Recycling Double-Pass Cross-Corrugated Solar Air Collectors

Ho, Chii‐Dong; Chang, Hsuan; Hsiao, Ching-Fang; Huang, Chien‐Chang

doi:10.3390/en11020338

Cited by 17 publications

(15 citation statements)

References 22 publications

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“…The recycle ratio of 1.8 yielded the largest thermohydraulic efficiency. Ho et al [13] utilized corrugated absorber and back plates to improve heat transfer in a double-pass SAH with recycled flow. It was shown that the thermal performance improved with an increasing recycle ratio and decreasing air flow rate.…”

Section: Introductionmentioning

confidence: 99%

Thermohydraulic Performance and Entropy Generation of a Triple-Pass Solar Air Heater with Three Inlets

2021

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In this paper, a triple-pass solar air heater with three inlets is analytically investigated. The effects of airflow ratios of the second and third passes (ranging from 0 to 0.4), and the Reynolds number of the third pass (ranging from 8000 to 18,000) on the thermohydraulic efficiency and entropy generation are assessed. An absorber plate equipped with rectangular fins on both sides is used to enhance heat transfer. The air temperature change in the passes is represented by ordinary differential equations and solved by numerical integration. The results demonstrate that the effect of the third pass airflow ratio on the thermohydraulic efficiency and entropy generation is more significant than that of the second pass airflow ratio. The difference in air temperature through the collector shows an insignificant reduction, but the air pressure loss is only 50% compared with that of a traditional triple-pass solar air heater. Increasing the air flow ratios dramatically reduces entropy generation. Multi-objective optimization found a Reynolds number of 11,156 for both the airflow ratio of the second pass of 0.258 and airflow ratio of the third pass of 0.036 to be the an optimal value to achieve maximum thermohydraulic efficiency and minimum entropy generation.

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Section: Introductionmentioning

confidence: 99%

Thermohydraulic Performance and Entropy Generation of a Triple-Pass Solar Air Heater with Three Inlets

2021

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“…The purpose of the present study is to develop the optimal design experimentally and theoretically and identify the best operational conditions such as the recycle ratio and air mass flow rate. The corrugated absorber configurations investigated in our previous study [33] showed that a significant enhancement of the thermal performance of solar air collectors was achieved. This motivated us to introduce various external-recycle operations to resolve the disadvantages of remixing effects and preserve the advantages of convective turbulent flows in the conventional flat-plate solar air heater upgraded through examining various configurations and operating conditions.…”

Section: Introductionmentioning

confidence: 92%

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

Chang

Hsiao

et al. 2021

Energies

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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.

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“…At this time, n, which is represented by a slope, is 0.6828. Therefore, Equation (16) can be written as Equation (18). At this time, n, which is represented by a slope, is 0.6828.…”

Section: Correlations For Nusselt Number (Nu) and Friction Factor (F)mentioning

confidence: 99%

“…At this time, n, which is represented by a slope, is 0.6828. Therefore, Equation (16) can be written as Equation (18).…”

Section: Correlations For Nusselt Number (Nu) and Friction Factor (F)mentioning

confidence: 99%

“…In addition to this, a number of studies have been conducted, and they mainly focused on the performance improvement by artificially roughened rip mounted on the absorber plater or modified absorber structure [14][15][16][17].Another technique to increase the heat-transfer performance of solar air heater is modifying the air duct or the shape of bottom plate in an air channel of the solar air heater. Ho et al [18] analyzed the performance of double-pass cross-corrugated solar air collector that has the wavelike-shaped absorbing plate and bottom plate. Singh [19] investigated the thermal performance of solar air heaters that have semicircular and triangular cross-sectioned duct under external recycle.…”

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confidence: 99%

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CFD Analysis on the Heat Transfer and Fluid Flow of Solar Air Heater having Transverse Triangular Block at the Bottom of Air Duct

Choi

2020

Energies

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In this study, a two-dimensional CFD (computational fluid dynamics) analysis was performed to investigate the heat-transfer and fluid-friction characteristics in a solar air heater having a transverse triangular block at the bottom of the air duct. The Reynolds number, block height (e), pitch (P), and length (l) were chosen as design parameters. The results are validated by comparing the Nusselt number predicted by simulation with available experimental results. Renormalization-group (RNG) k-ε model with enhanced wall-treatment was selected as the most appropriate turbulence model. From the results, it was found that the presence of a transverse triangular block produces a higher Nusselt number than that of smooth air duct. The enhancement in Nusselt number varied from 1.19 to 3.37, according to the geometric conditions investigated. However, the use of transverse triangular block also results in significantly higher friction losses. The thermohydraulic performance (THPP) was also estimated and has a maximum value of 1.001 for height (e) of 20 mm, length (l) of 120 mm, and pitch (P) of 150 mm, at Reynolds number of 8000. Furthermore, in the present study, correlations of the Nusselt number and friction factor were developed as a function of geometrical conditions of the transverse triangular block and Reynolds number, which can be used to predict the value of Nusselt number and friction factor with the absolute percentage deviations of 3.29% and 7.92%, respectively. solar air heater having non-uniform cross-section transverse rib roughness on the absorber plate. Akpinal and Koçyiǧit [7] analyzed the performance of a solar air heater supplied with various obstacles experimentally. Singh et al. [8] evaluated the effect of multiple arc-shaped ribs on the heat-transfer and friction characteristics, with various geometrical parameters. Singh et al. [9] investigated the heat and fluid-flow characteristics in a rectangular duct roughened with periodic discrete V-down rip. Kumar and Kim conducted a CFD-based analysis to investigate heat transfer and friction characteristics in rectangular channel with discrete multi-V-pattern ribs [10].The other method to improve the performance of a solar air heater is modifying the absorber plate. Karim and Hawlader [11] examined the performance of three types of solar air collectors having a flat-plate, v-corrugated, and finned absorber. Ho et al. [12] conducted an experimental and theoretical analysis of the double-pass cross-corrugated and double-pass V-corrugated solar air collector. Zheng et al. [13] performed experimental investigation of solar air heaters having perforating corrugated plate, slit-perforated plate, and corrugated packing. In addition to this, a number of studies have been conducted, and they mainly focused on the performance improvement by artificially roughened rip mounted on the absorber plater or modified absorber structure [14][15][16][17].Another technique to increase the heat-transfer performance of solar air heater is modifying the air duct or the shape ...

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Device Performance Improvement of Recycling Double-Pass Cross-Corrugated Solar Air Collectors

Cited by 17 publications

References 22 publications

Thermohydraulic Performance and Entropy Generation of a Triple-Pass Solar Air Heater with Three Inlets

Thermohydraulic Performance and Entropy Generation of a Triple-Pass Solar Air Heater with Three Inlets

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

CFD Analysis on the Heat Transfer and Fluid Flow of Solar Air Heater having Transverse Triangular Block at the Bottom of Air Duct

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