Experimental characterization and simulation of a fin-tube latent heat storage using high density polyethylene as PCM

Zauner, Christoph; Hengstberger, F.; Etzel, Mark R.; Lager, Daniel; Hofmann, René; Walter, Heimo

doi:10.1016/j.apenergy.2016.06.138

Cited by 86 publications

(39 citation statements)

References 25 publications

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“…In the literature, publications regarding design and optimization of PCM heat exchanger for storage in CSP applications can be found [13,14]. Several technologies have been investigated: encapsulated PCM for thermocline systems [15][16][17], shell and tube heat exchangers [18][19][20] implementing finned tubes [21,22], heat pipes [23] or metallic foam [24] for heat transfer enhancement. All these studies make extensively use of CFD tools, permitting accurate performance evaluation through 2D or 3D modelling.…”

Section: Introductionmentioning

confidence: 99%

Geometry optimization of a heat storage system for concentrated solar power plants (CSP)

et al. 2018

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In the present study, geometry optimization of a phase change material (PCM) heat storage system is presented. The existing PCM-fins heat exchanger system works at the back side of a solar receiver in order to minimize the effect of the solar radiation fluctuations inside the cavity. As initially designed, the system does not accomplish the expected design purposes and thus optimization is needed. Optimization is usually time-consuming and some algorithms need a starting point, therefore one suitable method is geometrical optimization which aims to find the optimal shape of a system for a given criteria and providing a rough optimal geometry. Here, constructal theory, 'point to volume', is applied to find the optimum shape factor of the elemental volume of the presented PCM-heat exchanger. With this methodology, an optimum ratio of the PCM and fin width and length is found and beyond that the method is extended to 'surface to volume' problem. Results have been numerically validated using a CFD software and demonstrate that it gives a very good approximation of the real optimum which can be used as initial configuration for further optimization through CFD simulation or other optimization methods that require a starting point.

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Section: Introductionmentioning

confidence: 99%

Geometry optimization of a heat storage system for concentrated solar power plants (CSP)

et al. 2018

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“…[27] [28,29] [28] different charging levels were evaluated, following the previous study carried out by Gasia et al [27]. Hence, the charging processes were stopped after a period of time (∆t CH ) which depended on the ratio of accumulated energy (RAE).…”

Section: Materials and Methods 21 Materialsmentioning

confidence: 99%

Influence of the storage period between charge and discharge in a latent heat thermal energy storage system working under partial load operating conditions

et al. 2019

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The supply intermittency of energy sources like solar energy or industrial waste heat should be properly addressed when studying latent heat thermal energy storage (TES) systems, since it might cause an incomplete melting/solidification of phase change materials (PCM). In the present paper, and experimental study was performed to analyse the storage period (also known as stand-by period) in a latent heat TES system working under partial load operating conditions and the effect of its duration on the subsequent discharging process. In the experimental set-up, 99.5 kg of high density polyethylene (HDPE) was used as PCM in a 0.154 m 3 storage tank based on the shell-and-tube heat exchanger concept. Four different percentages of charge were evaluated: 58%, 73%, 83% (partial charge), and 97% (full charge). Each charging level was followed by three different periods of storage: 25 min, 60 min, and 120 min. The fact of working at different levels of charge caused that in some regions of the TES system the PCM was not completely melted. Thus, at the end of the charging process different levels of thermal homogenisation were observed. However, during the storage period, the PCM temperature showed a tendency to homogenisation, which was influenced by the energy distribution within the PCM, the heat losses, and the duration of the storage period. Focusing on the discharging period, it was observed that the duration of the storage period slightly affected the temperature and heat transfer profiles, causing the main differences of performance during the first 30 min of process.

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“…[34] and Zauner et al. [35] carried out experiments on high temperature latent heat TES with an eutectic mixture of KNO

/NaNO

and high density polyethylene respectively and Garcia et al. [36] conducted numerical as well as experimental investigations on a pilot scale latent heat TES for CSP-applications.…”

Section: Introductionmentioning

confidence: 99%

Partial cycle operation of latent heat storage with finned tubes

et al. 2020

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This work examines a high temperature latent heat storage system, which could find use in future concentrated solar power and other combined heat and power plants. In contrast to lab-based fully charged or totally discharged states, partial load states will be the principal operation states in real-world applications. Hence, a closer look on the partial load states and the effective power rates are worthwhile for a successful implementation of this storage type. A vertical finned shell and tube heat exchanger pipe with a combination of transversal and longitudinal fins is applied. Sodium nitrate with a melting temperature of 306 is used as phase change material and thermal oil serves as heat transfer fluid. Temperatures in the storage and the heat transfer fluid as well as the mass flow are measured for data analysis. The state of charge formulation is based on an enthalpy distribution function, where the latent heat of fusion is spread over a specific temperature range. The data show consistently high power rates for all partial load cycles at any state of charge. The mean power rate for charging is 6.78 kW with an 95.45 % confidence interval of 1.14 kW for all cycles. The discharging power rate is −5.72 kW with a 95.45 % confidence interval of 1.36 kW for all cycles. The lowest power rate is measured for the full cycle at the end of charging/discharging. It is caused by a narrow volume, which is not penetrated by fins, near the perimeter of the cylindrical heat exchanger. The state of charge formulation correlates with the storage capacity and enables state of charge based cycling. With the energy balance of the storage, the data validity is proven and further storage parameters are determined. The energy density is as high as 110 kW h m −3 and a power rate of 2.28 kW m −1 for the finned tube is confirmed. These values are highly promising for further development and application of latent heat storage systems.

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Experimental characterization and simulation of a fin-tube latent heat storage using high density polyethylene as PCM

Cited by 86 publications

References 25 publications

Geometry optimization of a heat storage system for concentrated solar power plants (CSP)

Geometry optimization of a heat storage system for concentrated solar power plants (CSP)

Influence of the storage period between charge and discharge in a latent heat thermal energy storage system working under partial load operating conditions

Partial cycle operation of latent heat storage with finned tubes

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