Numerical Model for Storage Systems Based on Phase-Change Materials

2011 ◽  
Author(s):  
Adriano Sciacovelli ◽  
Vittorio Verda ◽  
Francesco Colella
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Materials ◽  
Storage Systems ◽  
Numerical Procedure ◽  
Thermal Storage ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Technical Problems

Phase-change materials (PCM) are particularly promising for thermal storage in various energy plants as solar plants, district heating, heat pumps, etc. mainly because of the possibility to reduce the volume of storage tanks, but also because the problems related with thermal stratification are considerably reduced. On the other hand, research is necessary in order to address technical problems, mainly related to the heat transfer in the medium, which needs to be enhanced in order to achieve reasonable charging and discharging processes. The present paper describes the application of computational fluid-dynamics (CFD) for the analysis of PCM thermal storage systems. The numerical analysis is directed at understanding the role of buoyancy-driven convection during constrained solidification and melting inside a shell-and-tube geometry. The 2D model is based on a finite-volume numerical procedure that adopts the enthalpy method to take in account the phase change phenomenon. The time-dependent simulations show the melting phase front and melting fraction of the PCM and incorporate the fluid flow in the liquid phase. The obtained temperature profiles are compared to a set of experimental data available in the literature. The results show that during the melting process natural convection within the PCM has non negligible effects on the behavior of the system. The numerical simulations of the solidification process show that the increasing solid fraction of the PCM inhibits the buoyancy in the remaining liquid portion of the phase-change-material. Furthermore, the paper discusses the effects on the phase-change processes of the main operating conditions, including inlet temperature and mass flow rate of the heat transfer fluid.

scholarly journals Numerical Modeling Prediction of Thermal Storage during Discharging Phase, PV- Thermal Solar and with Nanofluids

2021 ◽  
Vol 10 ◽  
pp. 1-18
Author(s):  
Samuel Sami Howard ◽  
Keyword(s):  
Heat Transfer ◽  
Hybrid System ◽  
Phase Change Materials ◽  
Thermal Storage ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Melting Time ◽  
Discharge Process ◽  
Fluid Temperature ◽  
System Efficiency

This study is intended to present a numerical model that was established after the energy conservation equations coupled with the heat transfer equations to predict the discharge behavior of different phase change materials, paraffin under the effect of different operating conditions such as solar radiation, heat transfer fluid, using nanofluids; AI2O3, CuO, Fe304 and SiO2, at different concentrations, and heat transfer fluid temperatures. Besides, the effect of the aforementioned operating conditions on the thermal storage process using PV-Thermal hybrid system and the thermal energy conversion efficiency is presented and discussed. It has been observed in this study that the nanofluid AI2O3 has the longest discharge duration elapse compared to other nanofluids and water as base heat transfer fluid. The nanofluid Ai2O3 as heat transfer fluid exhibited the longest time compared to other nanofluids and water as base heat transfer fluid. It was also shown that the higher the nanofluid volumetric concentrations, the longer the discharge process duration elapses. The data showed that nanofluid Al2O3 has the highest discharge time at different concentrations compared to the other nanofluids during the three regions solid, mushy, and liquid. The results clearly showed that by adding 5 % Fe304 nanoparticles, the melting time of paraffin could be saved by 16.5% over the water. It is also evident that the higher the heat transfer fluid temperature, the higher the hybrid system efficiency, and nanofluids CuO and SiO2 have the highest hybrid system efficiency compared to other nanofluids and water as heat transfer fluid. Finally, a good agreement has been obtained between the model and experimental data published in the literature.

scholarly journals Investigation of the dynamic characteristics of a thermal energy storage unit filled with multiple phase change materials

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 527-533 ◽  
Author(s):  
Xiaoyan Li ◽  
Rongpeng Huang ◽  
Xinyue Miao ◽  
Xuelei Wang ◽  
Yabin Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Storage Systems ◽  
Heat Transfer Fluid ◽  
Energy Storage Systems ◽  
Thermal Energy Storage Systems

In order to improve the thermal performance of thermal energy storage systems, a packed bed thermal energy storage systems unit using spherical capsules filled with multiple phase change materials (multi-PCM) for use in conventional air-conditioning systems is presented. A 3-D mathematical model was established to investigate the charging characteristics of the thermal energy storage systems unit. The optimum proportion between the multi-PCM was identified. The effects of heat transfer fluid-flow rate and heat transfer fluid inlet temperature on the liquid phase change materials volume fraction, charging time and charging capacity of the thermal energy storage system unit are studied. The results indicate that the charging capacity of multi-PCM units is higher than that of the conventional single-PCM (HY-2). For proportions 0:1:0, 2:3:3, 3:2:3, 3:3:2, 4:1:3, and 4:2:2, the charging capacity decreases by approximately 24.84%, 14.69%, 6.47%, 3.82%, and 1.13%, respectively, compared to the 4:2:2 proportion. Moreover, decreasing the heat transfer fluid inlet temperature can obviously shorten the complete charging time of the thermal energy storage systems unit.

Melting Process Expedition of Phase Change Materials via Silicone Oil

2018 ◽  
Author(s):  
Sarvenaz Sobhansarbandi ◽  
Fatemeh Hassanipour
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Transfer Enhancement ◽  
Phase Change Materials ◽  
Silicone Oil ◽  
Storage Systems ◽  
Ccd Camera ◽  
Melting Process ◽  
Operating Conditions ◽  
Transfer Enhancement

This paper presents a novel method of heat transfer enhancement and melting process expedition of phase change materials (PCMs) via silicone oil for the application in thermal energy storage systems. Sudden spot heating/cooling of the PCM causes a non-uniform melting process and in some cases the volume expansion/contraction. To avoid this malfunction, silicone oil can be applied in these systems to increase convective heat transfer (stirring effect). The feasibility of this method is investigated by two experimental analysis, one by having the mixture in a cylindrical container and one in a cubic container. The results from the images taken by Charge-Coupled Device (CCD) camera in the first analysis show a uniform melting process of the PCM. In the second analysis, the comparison is made for the two parallel setups with and without the silicone oil with the same operating conditions. The results show that in the system that lacks silicone oil, the paraffin starts melting after around 11 minutes from the heater start-up, while this time is around 6 minutes in the system with silicone oil. The effectiveness of silicone oil in enhancing the heat transfer rate is shown by a temperature rise of around 10 °C in the container. Applying PCMs in conjunction with silicone oil in various thermal storage systems for heating/cooling applications specifically in solar thermal collectors, enables heat transfer enhancement and consequently heat storage directly on the system.

Thermal Measurement System for Phase Change Materials

2012 ◽  
Author(s):  
R. Adinberg ◽  
D. Zvegilsky
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Materials ◽  
Heating Temperature ◽  
Thermal Storage ◽  
Potassium Nitrate ◽  
Heat Transfer Fluid ◽  
Analysis Model ◽  
Latent Heat Storage ◽  
Thermal Measurements

A lab scale set-up designed based on reflux heat transfer is used for studying latent heat storage for concentrating solar power systems. Phase change materials (PCM) with temperature of fusion range between 300 and 400°C are being tested using this system, including metal alloys and inorganic salts. In the present configuration, the system provides thermal measurements of PCM specimens of about 1000 g under heating temperature up to 450°C and enables simultaneous studying calorimetric properties of the loaded materials and heat transfer effects developed in the thermal storage process composed of charge and discharge phases. The measurement technique includes a thermal analysis model aimed at evaluating the experimental data. Results of the thermal measurements conducted with a thermal storage medium composed of potassium nitrate KNO3 (m.p. 334°C) as PCM and Diphyl (synthetic thermal oil, max working temperature 400°C) as the heat transfer fluid are presented and discussed in this study.

Natural Convection in an Enclosure With Blend of Micro Encapsulated Phase Change Materials

2013 ◽  
Author(s):  
Yasmin Khakpour ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Thermal Expansion ◽  
Natural Convection ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Numerical Study ◽  
Pure Water ◽  
Operating Conditions ◽  
Effective Density

This numerical study investigates the effect of using a blend of micro-encapsulated phase change materials (MEPCMs) on the heat transfer characteristics of a liquid in a rectangular enclosure driven by natural convection. A comparison has been made between the cases of using single component MEPCM slurry and a blend of two-component MEPCM slurry. The natural convection is generated by the temperature difference between two vertical walls of the enclosure maintained at constant temperatures. Each of the two phase change materials store latent heat at a specific range of temperatures. During phase change of the PCM, the effective density of the slurry varies. This results in thermal expansion and hence a buoyancy driven flow. The effects of MEPCM concentration in the slurry and changes in the operating conditions such as the wall temperatures compared to that of pure water have been studied. The MEPCM latent heat and the increased volumetric thermal expansion coefficient during phase change of the MEPCM play a major role in this heat transfer augmentation.

Solar thermal storage systems using phase change materials

1988 ◽  
Vol 12 (3) ◽  
pp. 547-555 ◽  
Author(s):  
D. Buddhi ◽  
N. K. Bansal ◽  
R. L. Sawhney ◽  
M. S. Sodha
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Storage Systems ◽  
Thermal Storage ◽  
Solar Thermal

Numerical Investigation of Flow and Heat Transfer Performance of Nano-Encapsulated Phase Change Material Slurry in Microchannels

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Sarada Kuravi ◽  
Krishna M. Kota ◽  
Jianhua Du ◽  
Louis C. Chow
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Numerical Investigation ◽  
Phase Change Material ◽  
Temperature Fields ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Bulk Fluid ◽  
Encapsulated Phase Change Material ◽  
Change Material

Microchannels are used in applications where large amount of heat is produced. Phase change material (PCM) slurries can be used as a heat transfer fluid in microchannels as they provide increased heat capacity during the melting of phase change material. For the present numerical investigation, performance of a nano-encapsulated phase change material slurry in a manifold microchannel heat sink was analyzed. The slurry was modeled as a bulk fluid with varying specific heat. The temperature field inside the channel wall is solved three dimensionally and is coupled with the three dimensional velocity and temperature fields of the fluid. The model includes the microchannel fin or wall effect, axial conduction along the length of the channel, developing flow of the fluid and not all these features were included in previous numerical investigations. Influence of parameters such as particle concentration, inlet temperature, melting range of the PCM, and heat flux is investigated, and the results are compared with the pure single phase fluid.

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