Close-contact melting in a horizontal cylindrical enclosure with longitudinal plate fins: Demonstration, modeling and application to thermal storage

Rozenfeld, Tomer; Kozak, Yoram; Hayat, Ron Rene; Ziskind, G.

doi:10.1016/j.ijheatmasstransfer.2015.02.064

Cited by 86 publications

(13 citation statements)

References 54 publications

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“…Close contact melting refers to the detachment of the solid from the boundary surface and the movement of solid into the liquid phase resulting in a small melting column [25]. Close contact melting enhances the melting rate of the PCM in the geometry.…”

Section: Close Contact Meltingmentioning

confidence: 99%

Numerical modelling of melting and settling of an encapsulated PCM using variable viscosity

et al. 2016

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demand and decrease pollution. This thermal energy can be stored and delivered back when needed.Latent heat thermal energy storage (LHTES) has become interesting to store thermal energy with a high storage density in a small temperature range. However, the low charging and discharging power of these units is due to the poor thermal conductivity of the phase change material (PCM) [2]. Macro-encapsulation of PCM may enhance the thermal distribution in thermal storage units by increasing the heat transfer area between the heat transfer fluid (HTF) and PCM. Macro-encapsulated PCM are already installed in different applications like ventilated façade [3], thermal storage units [4] etc. But different experimental set-ups are required to investigate and improve the efficiency of a thermal storage system. Therefore numerical modelling and simulation is employed to improve the efficiency and to reduce experimental efforts. Different simplified approaches exist to analyse macro-encapsulated PCM but they are limited to specific applications and are also less accurate in predicting the performance of thermal storage units. Computational fluid dynamics (CFD) simulations allow a more detailed view on the melting within macro-capsules. Therefore, Asako et al. [5], Assis et al. [6] and Rösler [7] developed different CFD models to study the melting of a PCM with settling in a capsule. In general, modelling the moving inter-facial boundary in melting and solidification has been of greater importance in many industrial and research applications. The Eulerian fixed grid approach is most common to model moving boundary interfaces for a solid-liquid phase change. Crank [8] delivered an initial idea of modelling moving boundary problems by considering just the diffusion in a phase change problem. Later different researchers have developed efficient methods of computing phase change problems including the convection in the liquid phase [9][10][11]. Solid-liquid Abstract Thermal energy storage units using macroencapsulated PCM in industrial and residential applications are contemporary due to better efficiency during charging and discharging. This article focuses on numerical modelling of the melting process in a macro-encapsulated PCM. Accounting the non-linear enthalpy-temperature relation and ramping down the velocity in solid phase is therefore fundamental. In the present article the variable viscosity method is implemented to ramp down the solid velocity and allow settling of the solid phase. This complete numerical model of melting and settling of PCM in a capsule is implemented in OpenFOAM. The numerical results for different solid viscosities are validated with experiments and show good agreement. The influence of the solid viscosity value and the pressure-velocity convergence is studied. It is observed that the pressure-velocity convergence only plays a greater role in the case where the computation of the exact solid velocity is required.

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Section: Close Contact Meltingmentioning

confidence: 99%

Numerical modelling of melting and settling of an encapsulated PCM using variable viscosity

et al. 2016

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“…In order to extend the range of application and to achieve better storage performances, research activities have been carried out to examine the heat transfer process [4,7,8]; storage types and configurations like a combination of different PCMs within one storage unit [9][10][11][12][13][14][15]; and the integration of highly heat conductive materials into the storage material, examples of which are copper, aluminum, stainless steel or carbon fiber [16][17][18][19][20][21][22]. These materials can be integrated in different forms, such as fins, honeycombs, wool or brush-form.…”

Section: Introductionmentioning

confidence: 99%

“…The most common way to improve the performance of shell-and-tube LTS is to integrate longitudinal or circular fins into the storage unit [16]. Khalifa et al [20] showed that the extracted energy per time of a LTS could be improved by 86% by adding four longitudinal fins into a shell-and-tube type LTS unit.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Shell-and-Tube Type Latent Thermal Energy Storage Performance with Different Arrangements of Circular Fins

2017

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Latent thermal energy storage (LTS) systems are versatile due to their high-energy storage density within a small temperature range. In shell-and-tube type storage systems fins can be used in order to achieve enhanced charging and discharging power. Typically, circular fins are evenly distributed over the length of the heat exchanger pipe. However, it is yet to be proven that this allocation is the most suitable for every kind of system and application. Consequently, within this paper, a simulation model was developed in order to examine the effect of different fin distributions on the performance of shell-and-tube type latent thermal storage units at discharge. The model was set up in MATLAB Simulink R2015b (The MathWorks, Inc., Natick, MA, USA) based on the enthalpy method and validated by a reference model designed in ANSYS Fluent 15.0 (ANSYS, Inc., Canonsburg, PA, USA). The fin density of the heat exchanger pipe was increased towards the pipe outlet. This concentration of fins was implemented linearly, exponentially or suddenly with the total number of fins remaining constant during the variation of fin allocations. Results show that there is an influence of fin allocation on storage performance. However, the average storage performance at total discharge only increased by three percent with the best allocation compared to an equidistant arrangement.

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“…5 Compared with the SHTES system, the main advantages of the LHTES system is the ability to provide higher energy storage density at relatively constant transition temperature using phase change materials (PCMs). [6][7][8][9] Among various LHTES systems, shell-andtube system has gained significant research attention due to its simple configuration and low cost. The shelland-tube system usually consists of a well-insulated shell and a concentric tube.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of dynamic melting process in a thermal energy storage system using U-tube heat exchanger

Xiong

Yong

Yang

2017

Advances in Mechanical Engineering

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A thermal energy storage system using U-tube heat exchanger is proposed and compared with the system using singletube heat exchanger. Based on the enthalpy-porosity method, three-dimensional numerical models using computational fluid dynamics approach are developed to simulate the dynamic melting of phase change material in the two systems. Variable specific heat technique and combined conduction-convection heat transfer models are applied to achieve precise simulation. The model is first validated using published data, and then, the heat flux across the tube is used to evaluate the heat transfer performance of the two systems. Moreover, parametric studies are performed to analyze the effect of heat transfer fluid flow rate on the U-tube system by six different cases. The results show that during the melting of phase change material, vertical temperature stratification occurs in both systems as a result of the intensified natural convection. The results also demonstrate that the U-tube system has better heat transfer performance than the singletube system which has the same heat transfer area and boundary conditions, reducing the total charging time by 25%. Increasing the heat transfer fluid flow rate greatly enhances the heat transfer performance for the U-tube system, but further enhancement is limited by the fixed heat transfer area. This study provides an effective method to investigate the thermal behavior of thermal energy storage using phase change materials, and the results can be helpful in optimizing the future thermal energy storage design and practical applications.

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Close-contact melting in a horizontal cylindrical enclosure with longitudinal plate fins: Demonstration, modeling and application to thermal storage

Cited by 86 publications

References 54 publications

Numerical modelling of melting and settling of an encapsulated PCM using variable viscosity

Numerical modelling of melting and settling of an encapsulated PCM using variable viscosity

Numerical Analysis of Shell-and-Tube Type Latent Thermal Energy Storage Performance with Different Arrangements of Circular Fins

Numerical investigation of dynamic melting process in a thermal energy storage system using U-tube heat exchanger

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