Numerical study of circular-elliptical double-pipe thermal energy storage systems

Bazai, H.; Moghimi, M.A.; Mohammed, Hayder I.; Mahani, Roohollah Babaei; Talebizadehsardari, Pouyan

doi:10.1016/j.est.2020.101440

Cited by 40 publications

(13 citation statements)

References 41 publications

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“…They stated that the phase change process is strongly affected by the fins placed in the inner tube. Bazai et al [50] numerically studied an elliptical tube implanted in an annulus channel, they investigated the effects of various aspect ratios and the angular position of the inner ellipse diameters during the charging process. They found that the maximum charging rate accelerated by 61% and the system performance improved by 26%.…”

Section: Introductionmentioning

confidence: 99%

Solidification Enhancement in a Triple-Tube Latent Heat Energy Storage System Using Twisted Fins

et al. 2021

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This work evaluates the influence of combining twisted fins in a triple-tube heat exchanger utilised for latent heat thermal energy storage (LHTES) in three-dimensional numerical simulation and comparing the outcome with the cases of the straight fins and no fins. The phase change material (PCM) is in the annulus between the inner and the outer tube, these tubes include a cold fluid that flows in the counter current path, to solidify the PCM and release the heat storage energy. The performance of the unit was assessed based on the liquid fraction and temperature profiles as well as solidification and the energy storage rate. This study aims to find suitable and efficient fins number and the optimum values of the Re and the inlet temperature of the heat transfer fluid. The outcomes stated the benefits of using twisted fins related to those cases of straight fins and the no-fins. The impact of multi-twisted fins was also considered to detect their influences on the solidification process. The outcomes reveal that the operation of four twisted fins decreased the solidification time by 12.7% and 22.9% compared with four straight fins and the no-fins cases, respectively. Four twisted fins improved the discharging rate by 12.4% and 22.8% compared with the cases of four straight fins and no-fins, respectively. Besides, by reducing the fins’ number from six to four and two, the solidification time reduces by 11.9% and 25.6%, respectively. The current work shows the impacts of innovative designs of fins in the LHTES to produce novel inventions for commercialisation, besides saving the power grid.

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Section: Introductionmentioning

confidence: 99%

Solidification Enhancement in a Triple-Tube Latent Heat Energy Storage System Using Twisted Fins

et al. 2021

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“…For one thing, since the thermal convection at the top (bottom) section is cooperation (competing) with the electro-convection as already mentioned, the melting rate at the top section for all aspect ratios is slightly higher than that in the bottom section, and thus the portion of the solid PCM at the bottom of the annular is melted slowly. For another, as reported by [10,66], the intensify of the thermal convection at the top section is relatively larger for a slender vertical-oriented elliptical, and this is also the main reason why the total melting time obtained for AR = 1/2 is smaller compared with the other cases.…”

Section: Resultsmentioning

confidence: 65%

“…However, in the lower region, owing to the opposite direction of these two forces, the melting front advances more sluggishly toward the bottom of the outer cylinder. The aspect ratio (AR = a/b) appeared in the aforementioned results is fixed at a constant value of 3/4, and as pointed out by some researchers [10,66] that the melting performance in the annular is also related to the the aspect ratio of the elliptical cylinder. In such a case, the influence of the aspect ratio of the inner elliptical electrode is studied in this paragraph, and all of the elliptical tubes considered here have identical area.…”

Section: Resultsmentioning

confidence: 95%

Electrohydrodynamic Enhancement of Phase Change Material Melting in Circular-Elliptical Annuli

Wang

Huang

2021

Energies

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Phase change material (PCM) has received significant attention due to its great potential for thermal energy storage. However, the major undesirable property of PCM is related to its low thermal conductivity. In this work, the electrohydrodynamic (EHD) enhancement of PCM melting in circular-elliptical annuli is investigated numerically by using the lattice Boltzmann method (LBM). The key motivation for our choice of the elliptical shape is due to the fact that the more curved elliptical surface corresponds to stronger charge injection strength, which may lead to stronger flow field, and the consequent increase of heat transfer rate. The influences of several non-dimensional parameters, including electric Rayleigh number T, thermal Rayleigh number (Ra) and the aspect ratio (AR) of the inner ellipse are investigated in detail. Based on the numerical results, it is found that the radial electro-convective flow induced by the external electric field makes a significant contribution to the enhancement of melting heat transfer, and specially, the maximum time saving in some cases is more than 85%. Moreover, we observe that when the Coulomb force is dominant over the buoyancy force, no matter the inner elliptical tube is oriented horizontally or vertically, the total melting times in these two cases are nearly the same, and the melting performance obtained for the circular electrode is usually better than the other cases. However, when the flow regime is dominated by the buoyancy force, the use of a slender vertical-oriented elliptical electrode instead of the circular one is more efficient.

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“…Therefore, several thermal efficiency improvement methods have been developed and applied to improve the heat transfer rate in the system [13,14]. These methods include adding fins and extended surfaces [15,16], modifying the geometry [17][18][19][20], porous media [21][22][23][24], heat tubes [25][26][27][28], composing thermally high conducting particles [29,30], multiple PCMs [31,32], nanoparticles [33,34], and using the combinations of different methods [35][36][37]. To enhance the natural convection in the system, multi-HTF tubes could be used, which is also valuable regarding the weight and cost of the design [38,39].…”

Section: Introductionmentioning

confidence: 99%

“…The optimization of the variable dependent factors to achieve a higher efficiency, lower cost, and smaller size have been studied by several researchers. Bazai et al [27] studied the thermal optimization of the circular elliptical double pipe-based TES unit. They detected the optimum values of the diameters of the pipes and the angular position.…”

Section: Introductionmentioning

confidence: 99%

Natural Convection Effect on Solidification Enhancement in a Multi-Tube Latent Heat Storage System: Effect of Tubes’ Arrangement

et al. 2021

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The solidification process in a multi-tube latent heat energy system is affected by the natural convection and the arrangement of heat exchanger tubes, which changes the buoyancy effect as well. In the current work, the effect of the arrangement of the tubes in a multi-tube heat exchanger was examined during the solidification process with the focus on the natural convection effects inside the phase change material (PCM). The behavior of the system was numerically analyzed using liquid fraction and energy released, as well as temperature, velocity and streamline profiles for different studied cases. The arrangement of the tubes, considering seven pipes in the symmetrical condition, are assumed at different positions in the system, including uniform distribution of the tubes as well as non-uniform distribution, i.e., tubes concentrated at the bottom, middle and the top of the PCM shell. The model was first validated compared with previous experimental work from the literature. The results show that the heat rate removal from the PCM after 16 h was 52.89 W (max) and 14.85 W (min) for the cases of uniform tube distribution and tubes concentrated at the bottom, respectively, for the proposed dimensions of the heat exchanger. The heat rate removal of the system with uniform tube distribution increases when the distance between the tubes and top of the shell reduces, and increased equal to 68.75 W due to natural convection effect. The heat release rate also reduces by increasing the temperature the tubes. The heat removal rate increases by 7.5%, and 23.7% when the temperature increases from 10 °C to 15 °C and 20 °C, respectively. This paper reveals that specific consideration to the arrangement of the tubes should be made to enhance the heat recovery process attending natural convection effects in phase change heat storage systems.

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Numerical study of circular-elliptical double-pipe thermal energy storage systems

Cited by 40 publications

References 41 publications

Solidification Enhancement in a Triple-Tube Latent Heat Energy Storage System Using Twisted Fins

Solidification Enhancement in a Triple-Tube Latent Heat Energy Storage System Using Twisted Fins

Electrohydrodynamic Enhancement of Phase Change Material Melting in Circular-Elliptical Annuli

Natural Convection Effect on Solidification Enhancement in a Multi-Tube Latent Heat Storage System: Effect of Tubes’ Arrangement

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