scholarly journals Phase Change Material Melting Process in a Thermal Energy Storage System for Applications in Buildings

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3254 ◽  
Author(s):  
Túlio Nascimento Porto ◽  
João M. P. Q. Delgado ◽  
Ana Sofia Guimarães ◽  
Hortência Luma Fernandes Magalhães ◽  
Gicelia Moreira ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Storage ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Melting Process ◽  
Average Heat ◽  
Change Material

The development of thermal energy storage systems is a possible solution in the search for reductions in the difference between the global energy supply and demand. In this context, the ability of some materials, the so-called phase change materials (PCMs), to absorb and release large amounts of energy under specific periods and operating conditions has been verified. The applications of these materials are limited due to their low thermal conductivity, and thus, it is necessary to associate them with high-conductivity materials, such as metals, to make the control of energy absorption and release times possible. Bearing this in mind, this paper presents a numerical analysis of the melting process of a PCM into a triplex tube heat exchanger (TTHX) with finned copper tubes, which allowed for the heat transfer between a heating fluid (water) and the phase change material to power a liquid-desiccant air conditioning system. Through the analysis of the temperature fields, liquid fractions, and velocities, as well as the phase transition, it was possible to describe the material charging process; then, the results were compared with experimental data, which are available in the specialized literature, and presented mean errors of less than 10%. The total required time to completely melt the PCM was about 105.5 min with the water being injected into the TTHX at a flow rate of 8.3 L/min and a temperature of 90 °C. It was observed that the latent energy that accumulated during the melting process was 1330 kJ, while the accumulated sensitive energy was 835 kJ. The average heat flux at the internal surface of the inner tube was about 3 times higher than the average heat flux at the outer surface of the TTHX intermediate tube due to the velocity gradients that developed in the internal part of the heat exchanger, and was about 10 times more intense than those observed in the external region of the equipment.

scholarly journals Designs of PCM based heat exchangers constructions for thermal energy storage tanks – examples and case study for selected design

2018 ◽  
Vol 70 ◽  
pp. 01010
Author(s):  
Marta Kuta ◽  
Dominika Matuszewska ◽  
Tadeusz Michał Wójcik
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
New Technologies ◽  
Tube Heat Exchanger ◽  
Change Material

Increasing energy consumption in residential and public buildings requires development of new technologies for thermal energy production and storage. One of possibilities for the second listed need is the use of phase change materials (PCMs). This work is focused on solutions in this area and consists of two parts. First one is focused on different designs of thermal energy storage (TES) tanks based on the phase change materials. The second part is the analysis of tests results for TES tank containing shelf and tube heat exchanger and filled with phase change material. Thermal energy storage tank is analyzed in order to use it in domestic heating and hot utility water installations. The aim of this research was to check the applicability of phase change material for mentioned purpose. Results show that using phase change materials for thermal energy storage can increase amount of stored heat. The use of properly selected PCM and heat exchanger enables the process of thermal energy storing and releasing to become more efficient.

scholarly journals Numerical modelling of phase change material melting process embedded in porous media: Effect of heat storage size

2019 ◽  
Vol 234 (3) ◽  
pp. 365-383 ◽  
Author(s):  
Pouyan Talebizadeh Sardari ◽  
Gavin S Walker ◽  
Mark Gillott ◽  
David Grant ◽  
Donald Giddings
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Porous Medium ◽  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Change Material

The aim of this paper is to study the influence of enclosure size in latent heat thermal energy storage systems embedded in a porous medium for domestic usage of latent heat thermal energy storage heat exchangers. A 2-D rectangular enclosure is considered as the computational domain to study the heat transfer improvement for a phase change material embedded in a copper foam considering a constant heat flux from the bottom surface. Different dimensions of the composite system are examined compared with a system without a porous medium. The thermal non-equilibrium model with enthalpy-porosity method is employed for the effects of porous medium and phase change in the governing equations, respectively. The phase change material liquid fraction, temperature, velocity, stream lines and the rate of heat transfer are studied. The presence of a porous medium increases the heat transfer significantly, but the improvement in melting performance is strongly related to the system's dimensions. For the dimensions of 200 × 100 mm (W × H), the melting time of porous-phase change material with the porosity of 95% is reduced by 17% compared with phase change material-only system. For the same storage volume and total amount of thermal energy added, the melting time is lower for the system with a lower height, especially for the phase change material-only system due to a higher area of the input heat. The non-dimensional analysis results in curve-fitting correlations between the liquid fraction and Fo.Ste.Ra −0.02 for rectangular latent heat thermal energy storage systems for both phase change material-only and composite-phase change material systems within the parameter range of 1.16 <  Ste < 37.13, 0 <  Fo < 1.5, 2.9 × 104 <  Ra < 9.5 × 108, 0 <  L f < 1 and 0 <  Fo.Ste.Ra −0.02 < 0.57. Over a range of system's volume, heat flux and surface area of the input heat flux, the benefit of composite phase change material is variable and, in some cases, is negligible compared with the phase change material-only system.

Thermal Energy Storage Through Melting of a Commercial Phase Change Material in an Annulus with Radially Divergent Longitudinal Fins

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Tonny Tabassum Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Operating Conditions ◽  
Melting Time ◽  
Bottom Part ◽  
Change Material

This study reports on the unsteady two-dimensional numerical investigations of melting of a paraffin wax (phase change material, PCM) which melts over a temperature range of 8.7oC. The PCM is placed inside a circular concentric horizontal-finned annulus for the storage of thermal energy. The inner tube is fitted with three radially diverging longitudinal fins strategically placed near the bottom part of the annulus to accelerate the melting process there. The developed CFD code used in Tabassum et al., 2018 is extended to incorporate the presence of fins. The numerical results show that the average Nusselt number over the inner tube surface, the total melt fraction, the total stored energy all increased at every time instant in the finned annulus compared to the annulus without fins. This is due to the fact that in the finned annulus, the fins at the lower part of the annulus promotes buoyancy-driven convection as opposed to the slow conduction melting that prevails at the bottom part of the plain annulus. Fins with two different heights have been considered. It is found that by extending the height of the fin to 50% of the annular gap about 33.05% more energy could be stored compared to the bare annulus at the melting time of 82.37 min for the identical operating conditions. The effects of fins with different heights on the temperature and streamfunction distributions are found to be different. The present study can provide some useful guidelines for achieving a better thermal energy storage system.

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