A simplified approach for modelling latent heat storages: Application and validation on two different fin-and-tubes heat exchangers

Neumann, Hannah; Palomba, Valeria; Frazzica, Andrea; Seiler, D.; Wittstadt, Ursula; Gschwander, Stefan; Restuccia, G.

doi:10.1016/j.applthermaleng.2017.06.142

Cited by 21 publications

(18 citation statements)

References 30 publications

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“…Although these expressions were retrieved considering a specific LHTS design with fixed operating parameters (such as water mass flow rate and temperatures), the proposed methodology can be easily tailored to different LHTS concepts and operating conditions. Indeed, the evolution of the LHTS heat rate highlighted by several studies [12,15,22] is comparable with the one expressed by Equations ( 8) and ( 9).…”

Section: Compact Modelsupporting

confidence: 74%

“…In an attempt to simplify the simulation of LHTS systems, Neumann et al [12] coupled a 1D model for the heat exchanger tubes and a reduced 3D model for the PCM and fins. This model can be used to improve the geometric and operational parameters of fin-and-tubes LHTSs with a limited computational effort, although the PCM parameters should be carefully calibrated.…”

Section: Introductionmentioning

confidence: 99%

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Compact Model of Latent Heat Thermal Storage for Its Integration in Multi-Energy Systems

et al. 2020

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Nowadays, flexibility through energy storage constitutes a key feature for the optimal management of energy systems. Concerning thermal energy, Latent Heat Thermal Storage (LHTS) units are characterized by a significantly higher energy density with respect to sensible storage systems. For this reason, they represent an interesting solution where limited space is available. Nevertheless, their market development is limited by engineering issues and, most importantly, by scarce knowledge about LHTS integration in existing energy systems. This study presents a new modeling approach to quickly characterize the dynamic behavior of an LHTS unit. The thermal power released or absorbed by a LHTS module is expressed only as a function of the current and the initial state of charge. The proposed model allows simulating even partial charge and discharge processes. Results are fairly accurate when compared to a 2D finite volume model, although the computational effort is considerably lower. Summarizing, the proposed model could be used to investigate optimal LHTS control strategies at the system level. In this paper, two relevant case studies are presented: (a) the reduction of the morning thermal power peak in District Heating systems; and (b) the optimal energy supply schedule in multi-energy systems.

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Section: Compact Modelsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Compact Model of Latent Heat Thermal Storage for Its Integration in Multi-Energy Systems

et al. 2020

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“…However, it is worth mentioning that the considered parameter is not precisely a processing capacity indicator, as many relevant factors in the studies are different, such as geometries, numerical configurations, solution methods, and the number of iterations per time step. The implementation of the numerical methods for solving melting and solidification problems in latent heat storage, as well as details about the accuracy, grid independence and validation codes using commercial software, as well as self-developed codes can be found in works [135,136]. It is worth emphasizing that the in-lab-scale or full-scale heat exchangers have also been discussed in the literature (see Zauner et al, 2016 [137]).…”

Section: Performance Evaluation Of Computers and Numerical Modelsmentioning

confidence: 99%

Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

et al. 2019

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Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy efficiency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-off methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in different container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations.

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“…The model can be simplified during solidification, since during this process natural convection does not occur. In [19], a simplified COMSOL model is implemented, in which a 3D model of only the portion of PCM between the fins is combined with a 1D model of the heat exchanger. The results for paraffin showed a good agreement with the experimental results, during both charge and discharge.…”

Section: Introductionmentioning

confidence: 99%

A Fast-Reduced Model for an Innovative Latent Thermal Energy Storage for Direct Integration in Heat Pumps

Palomba

Frazzica

2021

Applied Sciences

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In the present paper, the numerical modeling of an innovative latent thermal energy storage unit, suitable for direct integration into the condenser or evaporator of a heat pump is presented. The Modelica language, in the Dymola environment, and TIL libraries were used for the development of a modular model, which is easily re-usable and adaptable to different configurations. Validation of the model was carried out using experimental data under different operating modes and it was subsequently used for the optimization of a design for charging and discharge. In particular, since the storage unit is made up of parallel channels for the heat transfer fluid, refrigerant, and phase change material, their number and distribution were changed to evaluate the effect on heat transfer performance.

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A simplified approach for modelling latent heat storages: Application and validation on two different fin-and-tubes heat exchangers

Cited by 21 publications

References 30 publications

Compact Model of Latent Heat Thermal Storage for Its Integration in Multi-Energy Systems

Compact Model of Latent Heat Thermal Storage for Its Integration in Multi-Energy Systems

Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

A Fast-Reduced Model for an Innovative Latent Thermal Energy Storage for Direct Integration in Heat Pumps

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