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Journal ArticleDOI: 10.1080/10407782.2017.1376976

Numerical investigation of heat transfer enhancement in a multitube thermal energy storage heat exchanger using fins

25 Sep 2017-Numerical Heat Transfer Part A-applications (Taylor & Francis)-Vol. 72, Iss: 5, pp 389-400
Abstract: The application of a phase change material (PCM) as thermal energy storage observed unprecedented growth due to its large latent heat storage capacity at a constant temperature However, the design

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Topics: Phase-change material (67%), Heat transfer (66%), Plate fin heat exchanger (66%) ...read more
Citations
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Journal ArticleDOI: 10.1080/10407782.2019.1606634
Abstract: Melting thermal performance of a vertical cylindrical thermal energy storage unit is numerically investigated in presence of a phase change material (PCM) including Al2O3 nanoparticles (nano-PCM) a...

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Topics: Phase-change material (57%), Thermal energy storage (54%), Nano- (51%)

45 Citations


Journal ArticleDOI: 10.1016/J.EST.2019.03.024
Abstract: The present paper investigates melting and solidification processes in a multitube heat exchanger. The shell side is filled with paraffin (RT35) while water flows through the tube passes as the heat transfer fluid (HTF). The arrangements of one, two, three and four inner tubes cases are studied for HTF inlet temperatures of 70 °C, 75 °C and 80 °C. The thermal characteristics of the units involving melting front, heat transfer rate and Nusselt number are also analyzed. Results indicate that increasing the number of inner tubes results in a faster pace of melting and solidification. The effect is so pronounced that, when the HTF inlet temperature is 80 °C, application of 4-tube heat exchanger reduces the duration required for complete melting and solidification up to 43 and 50 percent, respectively as compared to the corresponding single-HTF-tube case. The results also show that by increasing the number of tubes, the surface-averaged Nusselt number decreases. This can be attributed to the inhibition of upper pipes against PCM melt movement. Also a correlation is proposed to calculate Nusselt number of tubes. Comparing the temperatures recorded by the thermocouples in rotational direction, it is indicated that the variation of the inner tube arrangement affects solidification process more than melting.

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Topics: Nusselt number (60%), Heat transfer (56%), Heat exchanger (54%)

12 Citations



Journal ArticleDOI: 10.1080/10407782.2019.1599273
Abstract: Employment of latent heat storage unit (LHSU) utilizing phase change material (PCM) in a substantial scale is constrained by the poor thermal conductivity of PCMs. Future utilization of LHSU will t...

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Topics: Phase-change material (63%), Heat transfer (58%), Shell and tube heat exchanger (57%) ...read more

11 Citations


Open accessJournal ArticleDOI: 10.1016/J.EGYR.2020.02.030
01 May 2020-Energy Reports
Abstract: In this study, a novel modified webbed tube heat exchanger was introduced and numerically investigated, to enhance the thermal performance of phase change material (PCM) thermal energy storage (TES) system. To evaluate the thermal performance for this heat exchanger its performance was compared with two types of heat exchanger. These heat exchangers included: the webbed tube heat exchanger and the triple tube heat exchanger. Two-dimensional numerical models were developed. The models enabled us to simulate conduction and natural convection heat transfer mechanisms. The process of solidification (discharging) was monitored during the simulation. The results showed that the PCM solidification process accelerates by 41% when utilizing the modified webbed tube heat exchanger compared to the webbed tube heat exchanger.

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Topics: Heat exchanger (60%), Phase-change material (59%), Thermal conduction (55%) ...read more

9 Citations


References
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Journal ArticleDOI: 10.1080/10407788808913615
A. D. Brent1, Vaughan R Voller1, K. J. Reid1Institutions (1)
Abstract: The melting of pure gallium in a rectangular cavity has been numerically investigated using the enthalpy-porosity approach for modeling combined convection-diffusion phase change. The major advantage of this technique is that it allows a fixed-grid solution of the coupled momentum and energy equations to be undertaken without resorting to variable transformations. In this work, a two-dimensional dynamic model is used and the influence of laminar natural-convection flow on the melting process is considered. Excellent agreement exists between the numerical predictions and experimental results available in the literature. The enthalpy-porosity approach has been found to converge rapidly, and is capable of producing accurate results for both the position and morphology of the melt front at different times with relatively modest computational requirements. These results may be taken to be a sound validation of this technique for modeling isothermal phase changes in metallurgical systems.

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Topics: Isothermal process (54%), Laminar flow (53%), Phase (matter) (51%) ...read more

1,110 Citations


Journal ArticleDOI: 10.1016/S0306-2619(02)00146-0
01 Jan 2003-Applied Energy
Abstract: The application of phase-change materials (PCM) for solar thermal-energy storage capacities has received considerable attention in recent years due to their large storage capacity and isothermal nature of the storage process. This study deals with the preparation and characterization of encapsulated paraffin-wax. Encapsulated paraffin particles were prepared by complex coacervation as well as spray-drying methods. The influence of different parameters on the characteristics and performance of a microencapsulated PCM in terms of encapsulation efficiency, and energy storage and release capacity has been investigated. The distribution of particle size and the morphology of microencapsulated PCM were analyzed by a scanning electron microscope (SEM). In the coacervation method, the optimum homogenizing time is 10 min and the amount of cross-linking agent is 6–8 ml. Results obtained from a differential scanning calorimeter (DSC) show that microcapsules prepared either by coacervation or the spray-drying method have a thermal energy storage/release capacity of about 145–240 J/g. Hence, encapsulated paraffin wax shows a good potential as a solar-energy storage material.

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Topics: Paraffin wax (52%), Energy storage (51%)

588 Citations


Journal ArticleDOI: 10.1016/S0038-092X(98)00128-5
Ramalingam Velraj1, R. V. Seeniraj1, B. Hafner2, Christian Faber2  +1 moreInstitutions (2)
01 Feb 1999-Solar Energy
Abstract: Commercial acceptance and the economics of solar thermal technologies are tied to the design and development of efficient, cost-effective thermal storage systems. Thermal storage units that utilize latent heat storage materials have received greater attention in the recent years because of their large heat storage capacity and their isothermal behavior during the charging and discharging processes. One major issue that needs to be addressed is that most phase-change materials (PCM) with high energy storage density have an unacceptably low thermal conductivity and hence heat transfer enhancement techniques are required for any latent heat thermal storage (LHTS) applications. In the present paper the various heat transfer enhancement methods for LHTS systems are discussed. Three different experiments to augment heat transfer were conducted and the findings are reported.

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Topics: Heat transfer (68%), Thermal energy storage (66%), Heat transfer enhancement (64%) ...read more

449 Citations


V. Shatikian1, Gennady Ziskind1, Ruth Letan1Institutions (1)
Abstract: The present study explores numerically the process of melting of a phase-change material (PCM) in a heat storage unit with internal fins open to air at its top. Heat is transferred to the unit through its horizontal base, to which vertical fins made of aluminum are attached. The phase-change material is stored between the fins. Its properties used in the simulations, including the melting temperature of 23–25 °C, latent and sensible specific heat, thermal conductivity and density in solid and liquid states, are based on a commercially available paraffin wax. A detailed parametric investigation is performed for melting in a relatively small system, 5–10 mm high, where the fin thickness varies from 0.15 mm to 1.2 mm, and the thickness of the PCM layers between the fins varies from 0.5 mm to 4 mm. The ratio of the PCM layer to fin thickness is held constant. The temperature of the base varies from 6 °C to 24 °C above the mean melting temperature of the PCM. Transient three- and two-dimensional simulations are performed using the Fluent 6.0 software, yielding temperature evolution in the fins and the PCM. The computational results show how the transient phase-change process, expressed in terms of the volume melt fraction of the PCM, depends on the thermal and geometrical parameters of the system, which relate to the temperature difference between the base and the mean melting temperature, and to the thickness and height of the fins. In search for generalization, dimensional analysis of the results is performed and presented as the Nusselt numbers and melt fractions vs. the Fourier and Stefan numbers and fin parameters. In some cases, the effect of Rayleigh number is significant and demonstrated.

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Topics: Fin (63%), Heat transfer (55%), Heat sink (53%) ...read more

289 Citations


Journal ArticleDOI: 10.1016/J.ENCONMAN.2013.05.003
Abstract: Thermal energy storage is critical for eliminating the discrepancy between energy supply and demand as well as for improving the efficiency of solar energy systems. This study numerically investigates the melting process in a triplex-tube heat exchanger with phase-change material (PCM) RT82. A two-dimensional numerical model is developed using the Fluent 6.3.26 software program. Three heating methods were used to melt the PCM from the inside tube, outside tube, and both tubes. Internal, external, and internal–external fin enhancement techniques were studied to improve the heat transfer between the PCM and heat transfer fluid. Enhancement techniques were compared with the inside tube heating, outside tube heating, both tube heating as well as the finned and internally finned tube. The effects of fin length on the enhancement techniques were investigated. Using a triplex-tube heat exchanger with internal–external fins, predicted results indicated that melting time is reduced to 43.3% in the triplex tube without fins. Experiments were conducted to validate the proposed model. Simulated results correspond with the experimental results.

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243 Citations


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