scholarly journals NUMERICAL STUDY OF THE GEOMETRIC INFLUENCE OF A FIN IN A CYLINDRICAL HEAT EXCHANGER FOR MELTING OF PCM

2019 ◽  
Vol 18 (1) ◽  
pp. 78
Author(s):  
F. C. Spengler ◽  
B. Oliveira ◽  
R. C. Oliveski ◽  
L. A. O. Rocha
Keyword(s):  
Heat Exchanger ◽  
Aspect Ratio ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Storage ◽  
Numerical Study ◽  
Melting Process ◽  
High Energy ◽  
High Energy Density ◽  
Melting Time

The thermal heat storage it’s an effective way to suit the energy availability with the demand schedule. It can be stored in the means of sensible or latent heat, the latter applying a material denominated Phase Change Material (PCM), which is provided as organic compounds, hydrated salts, paraffins, among others. The latent heat storage systems offer several advantages, like the practically isothermal process of loading and unloading and the high energy density. However, the low thermal conductivity makes the cycle prolonged on these systems, restricting its applicability. Applying computational fluid dynamics, the behavior of the PCM melting process was studied in cylindrical cavities with horizontal and vertical fins, aiming the optimization of the fin geometry. In this way the fin area was kept constant, varying its aspect ratio. The numerical model was validated with results from the literature and it’s composed of the continuity, momentum and energy equations increased by the phase change model. Qualitative and quantitative results are presented, referring to mesh independence, contours of velocity, net fraction and temperature at different moments of the process. The results of the study indicate that the position of the fin in the heat exchanger influences the melting process, although the vertical fins have a faster total melting process, horizontal fins can reach larger partial liquid fractions in less time in the heat exchanger. Such as the position of the fin, the increase of its length propitiates the reduction of the melting time, evidencing the optimal aspect ratio.

scholarly journals Effect of Twisted Fin Array in a Triple-Tube Latent Heat Storage System during the Charging Mode

2021 ◽  
Vol 13 (5) ◽  
pp. 2685
Author(s):  
Mohammad Ghalambaz ◽  
Jasim M. Mahdi ◽  
Amirhossein Shafaghat ◽  
Amir Hossein Eisapour ◽  
Obai Younis ◽  
...  
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Storage ◽  
Hot Water ◽  
Melting Time ◽  
Latent Heat Storage ◽  
Tube Heat Exchanger ◽  
Storage Rate

This study aims to assess the effect of adding twisted fins in a triple-tube heat exchanger used for latent heat storage compared with using straight fins and no fins. In the proposed heat exchanger, phase change material (PCM) is placed between the middle annulus while hot water is passed in the inner tube and outer annulus in a counter-current direction, as a superior method to melt the PCM and store the thermal energy. The behavior of the system was assessed regarding the liquid fraction and temperature distributions as well as charging time and energy storage rate. The results indicate the advantages of adding twisted fins compared with those of using straight fins. The effect of several twisted fins was also studied to discover its effectiveness on the melting rate. The results demonstrate that deployment of four twisted fins reduced the melting time by 18% compared with using the same number of straight fins, and 25% compared with the no-fins case considering a similar PCM mass. Moreover, the melting time for the case of using four straight fins was 8.3% lower than that compared with the no-fins case. By raising the fins’ number from two to four and six, the heat storage rate rose 14.2% and 25.4%, respectively. This study presents the effects of novel configurations of fins in PCM-based thermal energy storage to deliver innovative products toward commercialization, which can be manufactured with additive manufacturing.

Second-Law Efficiency of an Energy Storage-Removal Cycle in a Phase-Change Material Shell-and-Tube Heat Exchanger

1993 ◽  
Vol 115 (4) ◽  
pp. 240-243 ◽  
Author(s):  
Ch. Charach
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Latent Heat ◽  
Heat Storage ◽  
Latent Heat Storage ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Change Material

This communication extends the thermodynamic analysis of latent heat storage in a shell-and-tube heat exchanger, developed recently, to the complete heat storage-removal cycle. Conditions for the cyclic operation of this system are formulated within the quasi-steady approximation for the axisymmetric two-dimensional conduction-controlled phase change. Explicit expressions for the overall number of entropy generation units that account for heat transfer and pressure drop irreversibilities are derived. Optimization of this figure of merit with respect to the freezing point of the phase-change material and with respect to the number of heat transfer units is analyzed. When the frictional irreversibilities of the heat removal stage are negligible, the results of these studies are in agreement with those developed recently by De Lucia and Bejan (1991) for a one-dimensional latent heat storage system.

scholarly journals Role of honeycomb structure in improving the melting process of a phase change material inside a latent heat storage unit

2021 ◽  
Vol 19 ◽  
pp. 589-592
Author(s):  
M. Hariss ◽  
◽  
M. El Alami ◽  
A. Gounni
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Numerical Study ◽  
Melting Process ◽  
Honeycomb Structure ◽  
Melting Time ◽  
Storage Unit ◽  
Latent Heat Storage ◽  
The Impact

In this work, a numerical study is performed to analyze the impact of honeycomb structure on heat transfer within the PCM. The modeling is based on a transient calculation making it possible to analyze the phase change of the paraffin using the commercial software "Fluent" based on the enthalpy-porosity model. The results showed that the impregnation of a metal matrix in a rectangular enclosure helps to decrease the melting time and thus improve the heat transfer within the PCM.

scholarly journals Correlations for Melting Time and Melt Fraction for Bottom Charged Tube in Tube Phase Change Material Heat Exchanger

2021 ◽  
Author(s):  
Lanka Sandeep Raj ◽  
Sane Sreenivas ◽  
Bandaru Durga Prasad
Keyword(s):  
Reynolds Number ◽  
Rayleigh Number ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Storage ◽  
Melting Time ◽  
Time Step ◽  
Latent Heat Storage ◽  
Stefan Number ◽  
Hydraulic Behaviour

Abstract Multiple factors govern the Thermo-hydraulic behaviour of Latent heat storage devices. The correlation among these factors varies from case to case. In this work, a concentric tube in tube latent heat storage system is numerically modelled for the bottom charging case. Fixed grid enthalpy porosity approach is adopted to account for phase change. The numerical model’s independence is achieved by testing mesh size, time step, and maximum iterations per time step. The computational approach is validated against the experimental data. Non-dimensional parameters viz Rayleigh Number (3.04x105 to 65.75 x105), Stefan Number (0.2 to 1), Reynolds Number (600 to 3000), and L/D ratio (2 to 15) are varied in the respective ranges mentioned in parenthesis. Stefan number is found to have a major influence on the Melt Fraction and Melting time, compared to Rayleigh Number and Reynolds Number. Correlations are presented for quantifying the melt fraction and dimensionless melting time.

Zinc-rich eutectic alloys for high energy density latent heat storage applications

2017 ◽  
Vol 705 ◽  
pp. 714-721 ◽  
Author(s):  
E. Risueño ◽  
A. Faik ◽  
A. Gil ◽  
J. Rodríguez-Aseguinolaza ◽  
M. Tello ◽  
...  
Keyword(s):  
Energy Density ◽  
Latent Heat ◽  
Heat Storage ◽  
High Energy ◽  
High Energy Density ◽  
Eutectic Alloys ◽  
Latent Heat Storage

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

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7489
Author(s):  
Mohammadreza Ebrahimnataj Tiji ◽  
Jasim M. Mahdi ◽  
Hayder I. Mohammed ◽  
Hasan Sh. Majdi ◽  
Abbas Ebrahimi ◽  
...  
Keyword(s):  
Natural Convection ◽  
Heat Exchanger ◽  
Phase Change ◽  
Uniform Distribution ◽  
Latent Heat ◽  
Heat Storage ◽  
Heat Rate ◽  
Solidification Process ◽  
System Effect ◽  
Uniform Tube

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.

scholarly journals Numerical study on Finned Latent Heat Storage for Tri-generation System

2018 ◽  
Vol 4 (2) ◽  
pp. 119-129
Author(s):  
Guangya Zhu ◽  
Tin-Tai Chow
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Latent Heat ◽  
Heat Storage ◽  
High Energy ◽  
Pollutant Emissions ◽  
High Energy Density ◽  
Distinct Advantage ◽  
Generation System ◽  
Latent Heat Storage

Tri-generation system combines the supply of electric power, heating and cooling energy into one single system. Compared to the separated energy generation systems, the advantages lie in its higher efficiency, reliability and flexibility, as well as the reduced pollutant emissions. Yet the mismatch in system electricity and thermal demands often downgrades its effectiveness and economic merits. At this end, the adoption of thermal energy storage can be a practical means of improvement. Among the various choices, the finned latent heat storage using phase change material is distinct advantage owing to its high energy density. On the other hand, the finned latent heat storage design requires a detailed analysis of the heat transfer process. In this paper, our numerical model is introduced for use in simulating the associated complex heat transfer processes. The accuracy of the numerical model has been verified making use of the published experimental data available from the literature. Furthermore, our follow-up parametric study shows that the increase of fin thickness will improve the heat transfer performance for a given design configuration and the better heat transfer can be achieved with the reduction in fin length and fin spacing as well.

Review of Solar Cooking Using Latent Heat Storage

2014 ◽  
Vol 592-594 ◽  
pp. 1761-1765 ◽  
Author(s):  
Bhagwat Gore ◽  
Madhukar Tandale
Keyword(s):  
Phase Change ◽  
Latent Heat ◽  
Fossil Fuels ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Storage System ◽  
Melting Process ◽  
Latent Heat Storage ◽  
Endothermic Process ◽  
Increasing Demand

Use of latent heat storage system using Phase Change Materials (PCM) is an effective way of storing thermal energy and has several advantages like high storage density, isothermal nature of the energy storage etc. Solar cooking is one of the solutions to overcome increasing demand of fossil fuels in country like India. However it suffers from problems like low solar intensity, fluctuations during cloudy environment, limited availability (only during few hours of the day), and fluctuations with time. Use of latent heat storage system in solar cooking, can overcome some of the problems listed above. In this paper, efforts were made to gather the information on previous works on solar cooking system using PCM, use of Phase Change Materials (PCMs) for evening / night cooking and conceptual design of solar cooker using PCM. This review will be important for further research in this field. Heat storage system enables cooking food during cloudy sky or in the evening. Hence, solar cooker with PCM storage will increase the utility and reliability of the solar cookers. As the source temperature raises, the chemical bonds within the PCM breaks which changes phase from solid to liquid. The phase change is a heat-seeking (endothermic) process and therefore, the PCM absorbs heat on melting. Upon storing heat in the storage material, the material begins to melt when the phase change temperature is reached. The temperature then stays constant until the melting process is completed. The solar energy stored during day time can be used directly for cooking or can be stored in PCM and used during night/evening time.

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