Thermo-fluid dynamic model for horizontal packed bed thermal energy storages

The study investigates experimentally and numerically the problem of turbulent convective heat transfer and pressure drop in a packed bed with internal heat generation. The main objective is to develop correlations for the heat transfer between the bed and coolant as well as the pressure drop in the system using detailed experimental and 3-dimensional pore-scale numerical simulation. The system analysed is a horizontal circular channel filled with different stainless steel spheres with diameters of 5.5 mm, 6.5 mm and 7.5 mm. Dry air is used as working fluid. The study is performed for turbulent flow regimes with different Reynolds number (based on the spheres diameter) in the range of 900-2600. The spheres are heated using an electromagnetic induction heating method. Based on the experimental data, empirical correlations for turbulent pressure drop and convective heat transfer coefficient are developed.Results of pore-scale analysis show the complexity of the flow domain, which the velocity experiences a considerable increase compared to inlet velocity and is more evident in narrow gaps between spheres. Moreover, numerical results indicate the coupling of temperature and velocity fields, which a non-uniform velocity filed leads to non-uniform temperature distributions of air and solid spheres in the packed bed.

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“…In some studies, (e.g. [31,32]) the correlation proposed by Wakao and Kaguei [28] (Eq. ( 14)) is used for the packed bed energy storage system.…”

Section: Thermal Analysis Of the Packed Bedmentioning

confidence: 99%

Experimental and Pore-Scale Analysis of Flow and Thermal Fields in a Packed Bed Channel

Khaljani

Nazari

Azarpeyvand

et al. 2021

Heat Transfer Engineering

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“…Generally, the design of PBTES consists of a cylindrical or conical bed of rocks with air flowing in opposite vertical directions when charging and discharging the system. Designs with horizontal uniaxial flow with trapezoidal sections have been also considered [5,6]. The main weakness of the uniaxial approach is the difficulty to maintain a constant temperature throughout long discharge periods.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Packed bed systems are considered a promising energy storage option to overcome the variability of renewable energy sources in applications like solar-thermal power generation [1][2][3][4][5] or wind power [6]. According to these different authors, the main advantages over competing technologies are higher operating temperatures, the possibility to use ambient pressure air as heat transfer fluid and to be placed after the receiver without additional heat exchangers, its good scalability, operational robustness and simplicity, as well as the low cost of the materials used.…”

Section: Introductionmentioning

confidence: 99%

Modeling, Simulation and Optimal Operation of Multi-Extraction Packed-Bed Thermal Storage Systems

2020

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Solar thermal power technologies require storage systems to mitigate the natural variability of solar irradiation. Packed bed thermal storage systems (PBTES) offer a cost-effective solution using air as heat transfer fluid and rocks as a storage medium. Compared to its alternatives, however, PBTES presents a limited flexibility of operation due to the conventional unidirectional flow, which involves the progressive reduction of the outlet temperature during discharge and thus lowers the thermodynamic efficiency of the power cycle. The present study summarizes the progress on the design and optimal operation of a novel multi-extraction PBTES, a project that aims at mitigating its typically poor operational flexibility for solar power applications. To this end, a one-dimensional model with a high spatial resolution of a PBTES was developed, which includes four intermediate outlet points along the axial direction to investigate the benefits of optimal extraction operation. In order to reduce the computational burden, a coarser model of the storage system is used in combination with non-linear model predictive control (NLMPC). Through the optimal manipulation of the extraction valves, the output temperature is maintained close to a prescribed temperature throughout the discharge. The control admits not only constant temperature targets, but also time-varying scheduled profiles. This work describes the limitation of such a design and control approach and sets the direction for the future, more detailed analyses needed to demonstrate its applicability.

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Using concrete and other solid storage media in thermal energy storage systems

Laing-Nepustil¹,

Zunft²

2021

Advances in Thermal Energy Storage Systems

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Thermo-fluid dynamic model for horizontal packed bed thermal energy storages

Cited by 8 publications

References 8 publications

Experimental and Pore-Scale Analysis of Flow and Thermal Fields in a Packed Bed Channel

Experimental and Pore-Scale Analysis of Flow and Thermal Fields in a Packed Bed Channel

Modeling, Simulation and Optimal Operation of Multi-Extraction Packed-Bed Thermal Storage Systems

Using concrete and other solid storage media in thermal energy storage systems

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