Effects of synthetic oil nanofluids and absorber geometries on the exergetic performance of the parabolic trough collector

Okonkwo, Eric C.; Abid, Muhammad; Ratlamwala, Tahir Abdul Hussain

doi:10.1002/er.4099

Cited by 31 publications

(9 citation statements)

References 32 publications

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“…For example, Amina et al reported a 150% enhancement in heat transfer coefficient when using fins with nanofluids. In another study, the exergy enhancement achieved was approximately 16.51% when using twisted tape with Al 2 O 3 ‐thermal oil nanofluid (Okonkwo et al). For this method to be effective, clearly the nanofluid and the flow‐modifying insert have to be optimized simultaneously and synergistically.…”

Section: Further Discussionmentioning

confidence: 98%

An extensive review of various technologies for enhancing the thermal and optical performances of parabolic trough collectors

Abed

Afgan

2020

Int J Energy Res

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A wide range of engineering industrial applications require both the thermal and optical efficiencies of the system to be maximized with a reasonable low penalty for the friction factor and subsequently low losses in pressure. Among the family of concentrated solar power systems, parabolic trough collectors (PTCs), which have recently received significant attention, face similar challenges. The current work presents an extensive review of the PTC systems comparing recent and past technologies, which are widely being used to improve and enhance the thermal and optical efficiencies. Furthermore, the techniques used for single and two-phase flow modeling in numerical simulations, design variables, and experimental processes have been discussed in detail. The article also presents different numerical methods and analytical approaches of implementing the nonuniform solar distribution with different design parameters. Four main technologies are comprehensively addressed to effectively enhance the thermal performance of the PTCs; changing working heat transfer fluids, replacing the working fluids by nanofluids (single and hybrid) that have higher thermal-physical properties than those of base working fluids, inserting different tabulators with various design configurations, and finally combining the advantages of nanofluids and swirl generators in the same application. The article also critically summarizes the studies investigating the enhancement of thermal performance: use of novel design of PTCs and passive heat transfer enhancement techniques. Finally, a wide range of numerical and experimental studies are proposed for the future work related to the aforementioned main technologies. K E Y W O R D Sheat transfer enhancements, nanofluids, parabolic trough solar collectors, solar thermal energy, tabulators, thermal and optical performances

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Section: Further Discussionmentioning

confidence: 98%

An extensive review of various technologies for enhancing the thermal and optical performances of parabolic trough collectors

Abed

Afgan

2020

Int J Energy Res

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“…Friction factor of convergent‐divergent tube with artificial roughness “ e ” can be calculated using Churchill's correlation described by Okonkwo et al 58

\sqrt{\frac{2}{f}} = - 2.46 \ln ([], \frac{e}{D_{ri}} + {(\frac{7}{R_{e}})}^{0.9}) .

…”

Section: Thermodynamic Analysismentioning

confidence: 99%

Thermal and thermodynamic comparison of smooth and convergent‐divergent parabolic trough absorber tubes with the application of mono and hybrid nanofluids

et al. 2020

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Summary The utilization of hybrid nanofluids is a promising technique in the high temperature solar applications specially, parabolic trough collector (PTC). The purpose of the current research is to analyze, evaluate and compare the performance of PTC (converging‐diverging absorber tube) using mono and hybrid nanofluids to increase the convective heat transfer coefficient. To obtain this objective, converging‐diverging tube with sine geometry is examined as it enhances the turbulence in the flow due to increase in the inner surface roughness. The performance of the absorber tube is assessed for hybrid nanofluid (1.5% MWCNTs/therminol‐VPI and 1.5% TiO2/therminol‐VPI) as well as mono nanofluids (3% MWCNTs and 3% TiO2)/therminol‐VPI at a wide range of inlet temperature ranges from 350 K to 600 K. In order to compare the results of the converging‐diverging tube, a smooth absorber tube is also investigated at the same design conditions. Furthermore, our study comprises of the overall performance investigation about the exergy analysis, pressure drop, pumping power required and performance evaluation criteria to investigate the comprehensive performance of the absorber tubes. The results of the study reveal that the use of modified geometry with hybrid nanofluids considerably improves the performance of the system due to the presence of swirls and turbulence that will reduce absorber surface temperature and ultimately the heat losses. More specifically, the thermal efficiency enhancement for the converging‐diverging absorber tube with hybrid nanofluids ranges from 3.61% to 5.27%, while it is varied from 1.70% to 1.91% for smooth tube using hybrid nanofluids. Reynolds number ranges from 12 000 to 90 300 for hybrid nanofluid, while it is from 14 000 to 97 600 for pure therminol‐VPI. Furthermore, mean enhancement in the heat transfer coefficient using converging‐diverging tube with hybrid, TiO2 and MWCNTs therminol‐VPI‐based nanofluids are 1.72%, 0.67% and 0.70%, respectively at a mass flow rate of 0.6 kg/s and an ambient temperature of 300 K. The converging‐diverging/hybrid case has the values of 1.47 and 1.33 for performance evaluation criteria I and II, while all other cases has significantly less values compared to hybrid nanofluids. The thermal efficiency enhancement has a pressure‐drop penalty that leads to higher pumping power requirement; however, this requirement is very small as compared to the useful energy gain.

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“…Higher storage tank volume is recommended to yield higher thermal efficiency. Okonkwo et al [8] studied different configurations of absorber tube including smooth tube, finned tube, twisted tape inserted tube, and converging-diverging tube. The results exhibited that the converging-diverging absorber tube demonstrated the highest exergy efficiency.…”

Section: Introductionmentioning

confidence: 99%

One-Dimensional Modeling of Triple-Pass Concentric Tube Heat Exchanger in the Parabolic Trough Solar Air Collector

Phu¹,

Ngo²

2022

Heat Exchangers

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The parabolic trough solar collector has a very high absorber tube temperature due to the concentration of solar radiation. The high temperature leads to large heat loss to the environment which reduces efficiency of the parabolic trough collector. The heat loss reduction can be obtained by adopting a multi-pass fluid flow arrangement. In this chapter, airflow travels in three passes of the receiver to absorb heat from the glass covers and absorber tube to decrease surface temperatures. 1D mathematical model is developed to evaluate effective efficiency and the temperature distribution of surfaces and fluid. The mathematical modeling is based on air temperature gradients and solved by a numerical integration. Diameter ratios of outer glass to inner glass (r23) and inner glass to absorber tube (r12), Reynolds number (Re), and tube length (L) are varied to examine the efficiency and the temperature distribution. Results showed that the highest efficiency is archived at r23 = 1.55 and r12 in the range of 1.45 to 1.5. The efficiency increases with Re and decreases with L due to dominant heat transfer in terms of thermohydraulic behavior of a concentrating solar collector. With the optimum ratios, absorber tube temperature can reduce 15 K compared with another case.

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Effects of synthetic oil nanofluids and absorber geometries on the exergetic performance of the parabolic trough collector

Cited by 31 publications

References 32 publications

An extensive review of various technologies for enhancing the thermal and optical performances of parabolic trough collectors

An extensive review of various technologies for enhancing the thermal and optical performances of parabolic trough collectors

Thermal and thermodynamic comparison of smooth and convergent‐divergent parabolic trough absorber tubes with the application of mono and hybrid nanofluids

One-Dimensional Modeling of Triple-Pass Concentric Tube Heat Exchanger in the Parabolic Trough Solar Air Collector

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