An implicit algorithm for melting and settling of phase change material inside macrocapsules

Faden, Moritz; König-Haagen, Andreas; Höhlein, Stephan; Brüggemann, Dieter

doi:10.1016/j.ijheatmasstransfer.2017.10.033

Cited by 73 publications

(36 citation statements)

References 26 publications

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“…Air conditioning is not the ideal solution for lowering the temperature in a building, because it further increases energy consumption and requires rigorous maintenance to ensure air quality [15]. One of the ways to reduce the energy needs of a building is, therefore, the design of an energy-efficient envelope, limiting losses and recovering passive inputs as much as possible [16]. During the summer period, heat waves and high temperatures force the vulnerable population to consume more energy [17].…”

Section: Introductionmentioning

confidence: 99%

Energy Efficiency and Thermal Performance of Office Buildings Integrated with Passive Strategies in Coastal Regions of Humid and Hot Tropical Climates in Madagascar

2020

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Researchers have used passive strategies, such as the implementation of thermal insulation and the use of phase change materials (PCM), in several studies, but some problems have not yet been solved. It is the case of showing the real effect of external shading combined with thermal insulation and phase change materials to improve the thermal performance and energy efficiency of office buildings in tropical coastal areas. Another pending problem to be solved is to define the impact produced by passive strategies on the performance of workers in office buildings in coastal zones. It is with a view to answering all these questions that this study was envisaged with the main objective of evaluating, analyzing, comparing, and discussing the effect of thermal insulation and phase change materials on thermal comfort and energy demand in coastal areas of hot and humid tropical climates located in the island of Madagascar. In this sense, hourly climate data for the past 30 years have served as the basis for assessing environmental conditions of future climate. It was found that the PCMs have a more significant effect on the coastal zone of hot climates than humid tropical climates. The results of the statistical analyses showed that the application of passive strategies stabilizes indoor air temperatures to between 23 °C and 28 °C in the offices, which is the recommended comfort range in these regions. In the coastal regions of Madagascar, up to 30% of cooling energy is expected to be reduced by combining the introduction of thermal insulation and PCM materials.

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Section: Introductionmentioning

confidence: 99%

Energy Efficiency and Thermal Performance of Office Buildings Integrated with Passive Strategies in Coastal Regions of Humid and Hot Tropical Climates in Madagascar

2020

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“…However, when the solid density is more than that of the liquid PCM, the solid core moves downward during the melting process driven by the gravity force (sink effect). This effect is investigated in previous studies [22][23][24][25][26][27]. But, when there is no significant difference in the density, as in the present case, the solid core does not sink and the liquid is constrained.…”

Section: Liquid Fraction Status and Melt Streamlinesmentioning

confidence: 44%

Numerical Study of N-Eicosane Melting Inside a Horizontal Cylinder for Different Loading Rates

Benbrika¹,

Teggar²,

Benbelhout³

et al. 2020

IJHT

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This paper investigates numerically the melting of n-eicosane inside horizontal cylinders. The cylinders are embedded in a storage tank where hot air flows parallel to the cylinders during the charging process. The 2D mathematical model is based on the enthalpy-porosity method. To solve the conservation equations (continuity, momentum and energy), a CFD commercial software is employed. Numerical predictions are validated by comparison with benchmark results available in the literature. The melting characteristics of n-eicosane in horizontal cylinders are presented. The phase change dynamics, temperature distributions and melt flow patterns are analyzed. The effect of heating rate is investigated. Results show that after certain time natural heat convective currents have not the same positive effect on the melting rate due to the continuous heating of the upper melt in the enclosure; which contributes to lower the thermal charging time. Low heating rate (h=25 W m-2 K) intensifies this negative effect.

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“…It has been shown that axial conduction during flow is negligible and if the fluid capacitance is small, Equations and become:

\frac{\partial u}{∂Θ} = italicNTU ((), t_{s} - t_{HTF}); \frac{\partial t_{HTF}}{\partial ((), x / l)} = italicNTU ((), t_{HTF} - t_{s});

with ratio Θ = τ mc p,HTF / ρ s Al and effectiveness NTU = UPl/ ( mc p,HTF ), where A is the cross‐sectional area of the material, in m 2 and l is the length in the flow direction, in m. Verlaj et al:

normalρ \frac{\partial H}{\partial normalτ} = \frac{1}{r} \frac{∂}{\partial r} ((), normalλ r \frac{\partial t}{\partial r}) + \frac{1}{r} \frac{∂}{\partial normalθ} ((), \frac{λ}{r} \frac{\partial t}{\partial normalθ})

with phase change formula: solid region ( t ≤ t m −ε): H = c p t , interface ( t m −ε ≤ t ≤ t m + ε): H = c p t + ( L /2ε) t − t m + ε, and liquid region ( t ≥ t m + ε): H = c p t + L , where r is the radial coordinate, θ is the angular coordinate, and ε is the remittance. Faden et al:

c_{p} \frac{\partial t}{∂τ} + c_{p} \nabla ((), \overset{u}{true} t) - \nabla \cdot ((), \frac{λ}{ρ} \nabla t) = - L ((), \frac{\partial f}{\partial t} + \nabla ((), \overset{u}{true} f));

where: c p is the mixture heat capacity, in J/(kg K); t is the temperature, in K; τ is the time, in s;

\overset{u}{true}

is the velocity vector, in m/s; λis the mixture thermal conductivity, in W/(m K); ρ is the mixture density, in kg/m 3 ; L is the latent heat of fusion, in J/kg; and f is the phase fraction.…”

Section: Heat Transfer Analysismentioning

confidence: 99%

Review on heat transfer analysis in thermal energy storage using latent heat storage systems and phase change materials

2018

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Summary Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used later for heating and cooling applications and for power generation. TES has recently attracted increasing interest to thermal applications such as space and water heating, waste heat utilisation, cooling, and air conditioning. Phase change materials (PCMs) used for the storage of thermal energy as latent heat are special types of advanced materials that substantially contribute to the efficient use and conservation of waste heat and solar energy. This paper provides a comprehensive review on the development of latent heat storage (LHS) systems focused on heat transfer and enhancement techniques employed in PCMs to effectively charge and discharge latent heat energy, and the formulation of the phase change problem. The main categories of PCMs are classified and briefly described, and heat transfer enhancement technologies, namely dispersion of low‐density materials, use of porous materials, metal matrices and encapsulation, incorporation of extended surfaces and fins, utilisation of heat pipes, cascaded storage, and direct heat transfer techniques, are also discussed in detail. Additionally, a two‐dimensional heat transfer simulation model of an LHS system is developed using the control volume technique to solve the phase change problem. Furthermore, a three‐dimensional numerical simulation model of an LHS is built to investigate the quasi‐steady state and transient heat transfer in PCMs. Finally, several future research directions are provided.

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An implicit algorithm for melting and settling of phase change material inside macrocapsules

Cited by 73 publications

References 26 publications

Energy Efficiency and Thermal Performance of Office Buildings Integrated with Passive Strategies in Coastal Regions of Humid and Hot Tropical Climates in Madagascar

Energy Efficiency and Thermal Performance of Office Buildings Integrated with Passive Strategies in Coastal Regions of Humid and Hot Tropical Climates in Madagascar

Numerical Study of N-Eicosane Melting Inside a Horizontal Cylinder for Different Loading Rates

Review on heat transfer analysis in thermal energy storage using latent heat storage systems and phase change materials

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