Hydrothermal characteristics of a double flow parabolic trough solar collector equipped with sinusoidal-wavy grooved absorber tube and twisted tape insert

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ali Akbar Abbasian Arani ◽  
Ali Memarzadeh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Outer Surface ◽  
Solar Collector ◽  
Reynolds Numbers ◽  
Twisted Tape ◽  
Parabolic Trough ◽  
Content Type ◽  
Parabolic Trough Solar Collector

Purpose Present investigation conducts a study on the hydrothermal features of a double flow Parabolic Trough Solar Collector (PTSC) equipped with sinusoidal-wavy grooved absorber tube and twisted tape insert filled with nanofluid. This paper aims to present an effectual PTSC which is comprised by nanofluid numerically by means of finite volume method. Design/methodology/approach The beneficial results such as pressure drop inside the absorber tube, mean predicted friction factor, predicted average Nusselt number and hydrothermal Performance Evaluation Criteria (PEC) are evaluated and reported to present the influences of numerous factors on studied interest outcomes. Effects of different Reynolds numbers and environmental conditions are also determined in this investigation. Findings It is found that using the absorber roof (canopy) can enhance the heat transfer ratio of PTSCs significantly during all studied Reynolds numbers. Also, it is realized that the combination of inner grooved surface, outer corrugated surface and inserting turbulator can improve the thermal-hydraulic characteristics of PTSCs sharply. Originality/value Novel PTSC (N.PTSC) filling with two Heat Transfer Fluids (HTFs), inner and outer surface corrugated absorber tube, absorber roof and inserting twisted tape (N.PTSC.f) has the highest PEC values among all novel configurations along all investigated Reynolds numbers which is followed by configurations N.PTSC with two HTFs and inserting twisted tape (N.PTSC.e), N.PTSC with two HTFs and outer surface corrugated absorber tube (N.PTSC.b) and N.PTSC with two HTFs and inner surface corrugated absorber tube (N.PTSC.c), respectively. N.PTSC.f Nusselt number values can overcome the high values of friction factor, and therefore is introduced as the most efficient model in the current study.

Heat Transfer Enhancement in a Parabolic Trough Receiver Using Wall Detached Twisted Tape Inserts

2013 ◽  
Author(s):  
Aggrey Mwesigye ◽  
Tunde Bello-Ochende ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Difference ◽  
Reynolds Numbers ◽  
Heat Transfer Fluid ◽  
Twisted Tape ◽  
Parabolic Trough ◽  
Fluid Friction ◽  
Friction Performance ◽  
Volume Method

In this paper, heat transfer and fluid friction performance of a parabolic trough receiver with twisted tape inserts detached from the absorber tube’s wall is numerically studied. The numerical investigations were conducted for twist ratios in the range 0.30 ≤ ỹ ≤ 2.40, width ratios in the range 0.53 ≤ w̃ ≤ 0.91 and Reynolds numbers in the range 10,260 ≤ Re ≤ 320,000. The numerical simulations were performed using a finite volume method with the realisable k-ε turbulence model and Syltherm 800 as the heat transfer fluid. The use of twisted tape inserts shows a significant increase in the heat transfer and fluid friction performance of the receiver. The study also reveals significant reduction in absorber tube’s circumferential temperature difference due to the improved heat transfer performance. For the range of parameters considered, the Nusselt number, fluid friction and thermal enhancement factor are 1.01–3.36, 1.32–21.8, and 0.74–1.25 times those in a receiver with a plain absorber tube respectively. The absorber tube’s circumferential temperature difference reduces between 4–76% compared with a plain absorber tube. Correlations for Nusselt number and fluid friction are also reported for the range of parameters considered.

Heat transfer enhancement using second mode self-oscillating structures

2019 ◽  
Vol 30 (7) ◽  
pp. 3827-3842
Author(s):  
Samer Ali ◽  
Zein Alabidin Shami ◽  
Ali Badran ◽  
Charbel Habchi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Flow Regime ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Content Type ◽  
Laminar Flow Regime ◽  
Second Mode

Purpose In this paper, self-sustained second mode oscillations of flexible vortex generator (FVG) are produced to enhance the heat transfer in two-dimensional laminar flow regime. The purpose of this study is to determine the critical Reynolds number at which FVG becomes more efficient than rigid vortex generators (RVGs). Design/methodology/approach Ten cases were studied with different Reynolds numbers varying from 200 to 2,000. The Nusselt number and friction coefficients of the FVG cases are compared to those of RVG and empty channel at the same Reynolds numbers. Findings For Reynolds numbers higher than 800, the FVG oscillates in the second mode causing a significant increase in the velocity gradients generating unsteady coherent flow structures. The highest performance was obtained at the maximum Reynolds number for which the global Nusselt number is improved by 35.3 and 41.4 per cent with respect to empty channel and rigid configuration, respectively. Moreover, the thermal enhancement factor corresponding to FVG is 72 per cent higher than that of RVG. Practical implications The results obtained here can help in the design of novel multifunctional heat exchangers/reactors by using flexible tabs and inserts instead of rigid ones. Originality/value The originality of this paper is the use of second mode oscillations of FVG to enhance heat transfer in laminar flow regime.

Investigating the effect of nanoparticles diameter on turbulent flow and heat transfer properties of non-Newtonian carboxymethyl cellulose/CuO fluid in a microtube

2019 ◽  
Vol 29 (5) ◽  
pp. 1699-1723 ◽  
Author(s):  
Ali Rahimi Gheynani ◽  
Omid Ali Akbari ◽  
Majid Zarringhalam ◽  
Gholamreza Ahmadi Sheikh Shabani ◽  
Abdulwahab A. Alnaqi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Electronic Devices ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Vlsi Circuits ◽  
Convection Heat Transfer Coefficient ◽  
Content Type ◽  
Competing Interests

Purpose Although many studies have been conducted on the nanofluid flow in microtubes, this paper, for the first time, aims to investigate the effects of nanoparticle diameter and concentration on the velocity and temperature fields of turbulent non-Newtonian Carboxymethylcellulose (CMC)/copper oxide (CuO) nanofluid in a three-dimensional microtube. Modeling has been done using low- and high-Reynolds turbulent models. CMC/CuO was modeled using power law non-Newtonian model. The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Design/methodology/approach Present numerical simulation was performed with finite volume method. For obtaining higher accuracy in the numerical solving procedure, second-order upwind discretization and SIMPLEC algorithm were used. For all Reynolds numbers and volume fractions, a maximum residual of 10−6 is considered for saving computer memory usage and the time for the numerical solving procedure. Findings In constant Reynolds number and by decreasing the diameter of nanoparticles, the convection heat transfer coefficient increases. In Reynolds numbers of 2,500, 4,500 and 6,000, using nanoparticles with the diameter of 25 nm compared with 50 nm causes 0.34 per cent enhancement of convection heat transfer coefficient and Nusselt number. Also, in Reynolds number of 2,500, by increasing the concentration of nanoparticles with the diameter of 25 nm from 0.5 to 1 per cent, the average Nusselt number increases by almost 0.1 per cent. Similarly, In Reynolds numbers of 4,500 and 6,000, the average Nusselt number increases by 1.8 per cent. Research limitations/implications The numerical simulation was carried out for three nanoparticle diameters of 25, 50 and 100 nm with three Reynolds numbers of 2,500, 4,500 and 6,000. Constant heat flux is on the channel, and the inlet fluid becomes heated and exists from it. Practical implications The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Originality/value This manuscript is an original work, has not been published and is not under consideration for publication elsewhere. About the competing interests, the authors declare that they have no competing interests.

scholarly journals Investigating the impacts of included angles on flow and heat transfer in cross-corrugated triangular ducts with field synergy principle

2013 ◽  
Vol 17 (3) ◽  
pp. 823-832 ◽  
Author(s):  
Zuoyi Chen ◽  
Lizhi Zhang ◽  
Han Song
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Field Synergy ◽  
Field Synergy Principle ◽  
Included Angle ◽  
Flow And Heat Transfer ◽  
Performance Evaluation Criterion ◽  
Vital Effect

Included angles (?) have vital effect on the flow and heat transfer in cross-corrugated triangular ducts. The friction factor and Nusselt number were estimated at different Reynolds numbers from both experiments and simulations. Results show that the flow in the duck with ?=90 has the largest friction factor and Nusselt number. However, the included angle influences the flow and heat transfer in cross-corrugated triangular ducts in different ways. The field synergy principle was used to explore the mechanism of the different impacts of the included angle. Results show that the flow in the cross-corrugated triangular duct with ?=90o has the smallest domain averaged included angle (?m), which implies the best synergy performance. The results of the field synergy principle were also validated by analyzing the performance evaluation criterion and studying the velocity vector and temperature distributions.

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