Comparison of Stratification in a Water Tank and a PCM-Water Tank

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
A. Castell ◽  
C. Solé ◽  
M. Medrano ◽  
M. Nogués ◽  
L. F. Cabeza
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Materials ◽  
High Energy ◽  
Hot Water ◽  
The Other ◽  
High Energy Density ◽  
Water Tank ◽  
Charging And Discharging Processes ◽  
Thermal Energy Storage Systems

Most of the thermal energy storage systems available on the market use water as a storage medium. The improvement of the storage efficiency results in a higher performance of the whole system, and thermal stratification is commonly used for this purpose. On the other hand, in applications with small temperature changes, phase change materials (PCMs) provide high energy density since the latent heat is much larger than the sensible heat. This is the case of stratified hot water tanks, where the temperature change in the top layer is small as it is held close to the usage temperature. The benefits of using PCMs in a water tank, in terms of energy storage density, have been demonstrated before. The time with available hot water is increased because of the energy stored in the PCMs. The aim of this work is to demonstrate that the use of PCMs in the upper part of a water tank holds or improves the benefit of the stratification phenomenon. Two tanks with the same dimensions were compared during charging and discharging processes. One of them is a traditional water tank and the other is a PCM-water tank (a water tank with a phase change material placed at the top).

Comparison of Stratification in a Water Tank and a PCM-Water Tank

2007 ◽  
Author(s):  
A. Castell ◽  
C. Sole´ ◽  
M. Medrano ◽  
M. Nogue´s ◽  
L. F. Cabeza
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Temperature Change ◽  
High Energy ◽  
Hot Water ◽  
The Other ◽  
High Energy Density ◽  
Water Tank ◽  
Charging And Discharging Processes ◽  
Change Material

Most of the storage systems available on the market use water as storage medium. Enhancing the storage performance is necessary to increase the performance of most systems. The stratification phenomenon is employed to improve the efficiency of storage tanks. Heat at an intermediate temperature, not high enough to heat up the top layer, can still be used to heat the lower, colder layers. There are a lot of parameters to study the stratification in a water tank such as the Mix Number and the Richardson Number among others. The idea studied here was to use these stratification parameters to compare two tanks with the same dimensions during charging and discharging processes. One of them is a traditional water tank and the other is a PCM-water (a water tank with a Phase Change Material). A PCM is good because it has high energy density if there is a small temperature change, since then the latent heat is much larger than the sensible heat. On the other hand, the temperature change in the top layer of a hot water store with stratification is usually small as it is held as close as possible at or above the temperature for usage. In the system studied the Phase Change Material is placed at the top of the tank, therefore the advantages of the stratification still remain. The aim of this work is to demonstrate that the use of PCM in the upper part of a water tank holds or improves the benefit of the stratification phenomenon.

Compact Heat Storage for Solar Heating Systems

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Viktoria Martin ◽  
Fredrik Setterwall
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Average Power ◽  
High Capacity ◽  
High Energy ◽  
Finned Tube ◽  
Hot Water ◽  
High Energy Density ◽  
Power Capacity ◽  
Tube Heat Exchanger

Energy and cost efficient solar hot water systems require some sort of integrated storage, with high energy density and high power capacity for charging and discharging being desirable properties of the storage. This paper presents the results and conclusions from the design, and experimental performance evaluation of high capacity thermal energy storage using so-called phase change materials (PCMs) as the storage media. A 140 l 15 kW  h storage prototype was designed, built, and experimentally evaluated. The storage tank was directly filled with the PCM having its phase change temperature at 58°C. A tube heat exchanger for charging and discharging with water was submerged in the PCM. Results from the experimental evaluation showed that hot water can be provided with a temperature of 40°C for more than 2 h at an average power of 3 kW. The experimental results also show that it is possible to charge the 140 l storage with close to the theoretically calculated value of 15 kW h. Hence, this is a PCM storage solution with a storage capacity of over 100 kW h/m3, and an average power capacity during discharging of over 20 kW/m3. However, it is desirable to increase the heat transfer rate within the prototype. A predesign of using a finned-tube coil instead of an unfinned coil show that by using finned tube, the power capacity for discharging can be at least doubled, if not tripled.

scholarly journals Solvothermal method as a green chemistry solution for micro-encapsulation of phase change materials for high temperature thermal energy storage

2018 ◽  
Vol 5 ◽  
pp. 4 ◽  
Author(s):  
Albert Ioan Tudor ◽  
Adrian Mihail Motoc ◽  
Cristina Florentina Ciobota ◽  
Dan. Nastase Ciobota ◽  
Radu Robert Piticescu ◽  
...  
Keyword(s):  
High Temperature ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Solvothermal Method ◽  
High Energy ◽  
High Energy Density ◽  
Latent Heat Storage

Thermal energy storage systems using phase change materials (PCMs) as latent heat storage are one of the main challenges at European level in improving the performances and efficiency of concentrated solar power energy generation due to their high energy density. PCM with high working temperatures in the temperature range 300–500 °C are required for these purposes. However their use is still limited due to the problems raised by the corrosion of the majority of high temperature PCMs and lower thermal transfer properties. Micro-encapsulation was proposed as one method to overcome these problems. Different micro-encapsulation methods proposed in the literature are presented and discussed. An original process for the micro-encapsulation of potassium nitrate as PCM in inorganic zinc oxide shells based on a solvothermal method followed by spray drying to produce microcapsules with controlled phase composition and distribution is proposed and their transformation temperatures and enthalpies measured by differential scanning calorimetry are presented.

scholarly journals Nano-Enhanced Phase Change Materials in Latent Heat Thermal Energy Storage Systems: A Review

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3821
Author(s):  
Kassianne Tofani ◽  
Saeed Tiari
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Storage Systems ◽  
Heat Pipes ◽  
Energy Storage Systems ◽  
Thermal Energy Storage Systems

Latent heat thermal energy storage systems (LHTES) are useful for solar energy storage and many other applications, but there is an issue with phase change materials (PCMs) having low thermal conductivity. This can be enhanced with fins, metal foam, heat pipes, multiple PCMs, and nanoparticles (NPs). This paper reviews nano-enhanced PCM (NePCM) alone and with additional enhancements. Low, middle, and high temperature PCM are classified, and the achievements and limitations of works are assessed. The review is categorized based upon enhancements: solely NPs, NPs and fins, NPs and heat pipes, NPs with highly conductive porous materials, NPs and multiple PCMs, and nano-encapsulated PCMs. Both experimental and numerical methods are considered, focusing on how well NPs enhanced the system. Generally, NPs have been proven to enhance PCM, with some types more effective than others. Middle and high temperatures are lacking compared to low temperature, as well as combined enhancement studies. Al2O3, copper, and carbon are some of the most studied NP materials, and paraffin PCM is the most common by far. Some studies found NPs to be insignificant in comparison to other enhancements, but many others found them to be beneficial. This article also suggests future work for NePCM and LHTES systems.

scholarly journals Thermal performance evaluation of a new structure hot water tank integrated with phase change materials

2019 ◽  
Vol 158 ◽  
pp. 5034-5040
Author(s):  
Di Qin ◽  
Zhun (Jerry) Yu ◽  
Tingting Yang ◽  
Shuishen Li ◽  
Guoqiang Zhang
Keyword(s):  
Performance Evaluation ◽  
Phase Change ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Hot Water ◽  
Water Tank

Analysis of Flow Through Packed Bed of Spheres Containing Phase Change Materials for Thermal Energy Storage Applications

2019 ◽  
Author(s):  
Vinit V. Prabhu ◽  
Ethan Languri ◽  
Kashif Nawaz
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Response Time ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Response Rate ◽  
Packed Bed ◽  
Hot Water

Abstract The research on thermal energy storage (TES) systems have received a lot of attention in recent decades for sustainable use of thermal energy in various industrial and residential applications. The existing challenge in designing the TES is the response time of charging and discharging cycles that keeps these systems away from wide utilization in industries. Literature data show that beside the low thermal conductivity of most phase change materials (PCMs) as active media in TES systems, the poor flow distribution may be another factor affecting the response rate. This study aims to considerably reduce the response time by packing the PCMs in a bed of spheres made of high thermal conductivity material. The response rate during the charging cycle is studied numerically by passing hot water at 70 °C over the packed bed of spheres. The numerical analysis is performed using ANSYS Fluent 19. The PCM used in this study is a paraffin and has a melting point of 48 °C. The response rate of the system is studied and it is compared to other similar systems mentioned in literature. The amount of energy storage is also studied by changing the flow rate of water.

scholarly journals The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4840
Author(s):  
Ewelina Radomska ◽  
Lukasz Mika ◽  
Karol Sztekler ◽  
Lukasz Lis
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Storage Systems ◽  
Energy Storage Systems ◽  
Thermal Energy Storage Systems

An application of latent heat thermal energy storage systems with phase change materials seems to be unavoidable in the present world. The latent heat thermal energy storage systems allow for storing excessive heat during low demand and then releasing it during peak demand. However, a phase change material is only one of the components of a latent heat thermal energy storage system. The second part of the latent heat thermal energy storage is a heat exchanger that allows heat transfer between a heat transfer fluid and a phase change material. Thus, the main aim of this review paper is to present and systematize knowledge about the heat exchangers used in the latent heat thermal energy storage systems. Furthermore, the operating parameters influencing the phase change time of phase change materials in the heat exchangers, and the possibilities of accelerating the phase change are discussed. Based on the literature reviewed, it is found that the phase change time of phase change materials in the heat exchangers can be reduced by changing the geometrical parameters of heat exchangers or by using fins, metal foams, heat pipes, and multiple phase change materials. To decrease the phase change material’s phase change time in the tubular heat exchangers it is recommended to increase the number of tubes keeping the phase change material’s mass constant. In the case of tanks filled with spherical phase change material’s capsules, the capsules’ diameter should be reduced to shorten the phase change time. However, it is found that some changes in the constructions of heat exchangers reduce the melting time of the phase change materials, but they increase the solidification time.

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