Phase Change Material’s (PCMs) Effectiveness Index for Rapid Assessment in Thermal Management of Transient Pulse Electronics

2021 ◽  
Author(s):  
Adrian Olivera ◽  
Jhonathan Rosales ◽  
Pedro O. Quintero
Keyword(s):  
Experimental Data ◽  
Heat Source ◽  
Phase Change ◽  
Power Electronics ◽  
Latent Heat ◽  
Metal Nanoparticle ◽  
Melting Time ◽  
Melting Front ◽  
Typical Application ◽  
Linear Temperature

Abstract The use of nanocomposites phase change materials (PCMs) as transient passive thermal solution for high power electronics have been growing in the last few years. Typical application loads are in timescales of seconds, milliseconds, or nanoseconds; where the use of traditional cooling solutions, designed for steady state conduction/convection, are no longer effective. Common combinations for nanocomposites, with a PCM matrix and metal nanoparticle fillers, are Wax-Ag/Au or Sugars-Ag/Au. However, there is a lack of a performance parameter to guide the decision making during the co-design process. In this investigation we propose the formulation of an effectiveness parameter (index), in terms of response time and effective PCM volume selection, to assist the tradeoff analysis required for complex systems. The index is defined by the ratio of the PCM volume’s phase change time to the melting time. When heating a PCM, with a finite thickness, a melt front is formed as soon as the interface with the heat source begins melting while the heat source continues adding energy into the material. This melting front will achieve a constant velocity through the thickness owing to the high volumetric latent heat; therefore, the volume changes phase with an accompanying linear temperature increase. This non-isothermal phenomenon drives the definition of our proposed phase change energy term, or modified latent heat, for non-isothermal transient phase changing systems such as those encountered in pulsed power electronics. The calculated modified latent heat was validated, with a 1.68% difference, when compared to Field’s metal experimental data using a 12W heater and the Temperature-Energy diagram. Furthermore, a 0.39% difference was obtained between the calculated modified latent heat of organic PCM PT-58 and the experimental data with a 2W heater.

Thermal Behavior of Phase Change Material During Charging Inside a Finned Cylindrical Latent Heat Energy Storage System: Effects of the Arrangement and Number of Fins

2010 ◽  
Author(s):  
Dominic Groulx ◽  
Wilson Ogoh
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Latent Heat ◽  
Storage System ◽  
Heat Energy ◽  
Hot Water ◽  
Heat Of Fusion ◽  
Melting Front ◽  
Change Material

One way of storing thermal energy is through the use of latent heat energy storage systems. One such system, composed of a cylindrical container filled with paraffin wax, through which a copper pipe carrying hot water is inserted, is presented in this paper. It is shown that the physical processes encountered in the flow of water, the heat transfer by conduction and convection, and the phase change behavior of the phase change material can be modeled numerically using the finite element method. Only charging (melting) is treated in this paper. The appearance and the behavior of the melting front can be simulated by modifying the specific heat of the PCM to account for the increased amount of energy, in the form of latent heat of fusion, needed to melt the PCM over its melting temperature range. The effects of adding fins to the system are also studied, as well as the effects of the water inlet velocity.

scholarly journals NUMERICAL STUDY OF THE GEOMETRIC INFLUENCE OF A FIN IN A CYLINDRICAL HEAT EXCHANGER FOR MELTING OF PCM

2019 ◽  
Vol 18 (1) ◽  
pp. 78
Author(s):  
F. C. Spengler ◽  
B. Oliveira ◽  
R. C. Oliveski ◽  
L. A. O. Rocha
Keyword(s):  
Heat Exchanger ◽  
Aspect Ratio ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Storage ◽  
Numerical Study ◽  
Melting Process ◽  
High Energy ◽  
High Energy Density ◽  
Melting Time

The thermal heat storage it’s an effective way to suit the energy availability with the demand schedule. It can be stored in the means of sensible or latent heat, the latter applying a material denominated Phase Change Material (PCM), which is provided as organic compounds, hydrated salts, paraffins, among others. The latent heat storage systems offer several advantages, like the practically isothermal process of loading and unloading and the high energy density. However, the low thermal conductivity makes the cycle prolonged on these systems, restricting its applicability. Applying computational fluid dynamics, the behavior of the PCM melting process was studied in cylindrical cavities with horizontal and vertical fins, aiming the optimization of the fin geometry. In this way the fin area was kept constant, varying its aspect ratio. The numerical model was validated with results from the literature and it’s composed of the continuity, momentum and energy equations increased by the phase change model. Qualitative and quantitative results are presented, referring to mesh independence, contours of velocity, net fraction and temperature at different moments of the process. The results of the study indicate that the position of the fin in the heat exchanger influences the melting process, although the vertical fins have a faster total melting process, horizontal fins can reach larger partial liquid fractions in less time in the heat exchanger. Such as the position of the fin, the increase of its length propitiates the reduction of the melting time, evidencing the optimal aspect ratio.

Analysis of a Latent Heat Storage Device With Radial Fins

2013 ◽  
Author(s):  
Y. Kozak ◽  
T. Rozenfeld ◽  
G. Ziskind
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Latent Heat ◽  
Close Contact ◽  
Thermal Storage ◽  
Ambient Air ◽  
Contact Melting ◽  
Storage Device ◽  
Melting Time ◽  
Cfd Model

Phase-change materials (PCMs) can store large amounts of heat without significant change of their temperature during the phase-change process. This effect may be utilized in thermal energy storage, especially for solar-thermal power plants. In order to enhance the rate of heat transfer into PCMs, one of the most common methods is the use of fins which increase the heat transfer area that is in contact with the PCM. The present work deals with a latent heat thermal storage device that uses a finned tube with an array of radial fins. A heat transfer fluid (HTF) flows through the tube and heat is conducted from the tube to the radial fins that are in contact with the bulk of the PCM inside a cylindrical shell. The thermal storage charging/discharging process is driven by a hot/cold HTF inside the tube that causes the PCM to melt/solidify. The main objective of the present work is to demonstrate that close-contact melting (CCM) can affect the storage unit performance. Accordingly, two different types of experiments are conducted: with the shell exposed to ambient air and with the shell submerged into a heated water bath. The latter is done to separate the PCM from the shell by a thin molten layer, thus enabling the solid bulk to sink. The effect of the solid sinking and close-contact melting on the fins is explored. It is found that close-contact melting shortens the melting time drastically. Accordingly, two types of models are used to predict the melting rate: numerical CFD model and analytical/numerical close-contact melting model. The CFD model takes into account convection in the melt and the PCM property dependence on temperature and phase. The analytical/numerical CCM model is developed under several simplifying assumptions. Good agreement is found between the predictions and corresponding experimental results.

scholarly journals Correlations for Melting Time and Melt Fraction for Bottom Charged Tube in Tube Phase Change Material Heat Exchanger

2021 ◽  
Author(s):  
Lanka Sandeep Raj ◽  
Sane Sreenivas ◽  
Bandaru Durga Prasad
Keyword(s):  
Reynolds Number ◽  
Rayleigh Number ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Storage ◽  
Melting Time ◽  
Time Step ◽  
Latent Heat Storage ◽  
Stefan Number ◽  
Hydraulic Behaviour

Abstract Multiple factors govern the Thermo-hydraulic behaviour of Latent heat storage devices. The correlation among these factors varies from case to case. In this work, a concentric tube in tube latent heat storage system is numerically modelled for the bottom charging case. Fixed grid enthalpy porosity approach is adopted to account for phase change. The numerical model’s independence is achieved by testing mesh size, time step, and maximum iterations per time step. The computational approach is validated against the experimental data. Non-dimensional parameters viz Rayleigh Number (3.04x105 to 65.75 x105), Stefan Number (0.2 to 1), Reynolds Number (600 to 3000), and L/D ratio (2 to 15) are varied in the respective ranges mentioned in parenthesis. Stefan number is found to have a major influence on the Melt Fraction and Melting time, compared to Rayleigh Number and Reynolds Number. Correlations are presented for quantifying the melt fraction and dimensionless melting time.

scholarly journals New Equivalent Thermal Conductivity Model for Size-Dependent Convection-Driven Melting of Spherically Encapsulated Phase Change Material

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4752
Author(s):  
Feng Hou ◽  
Shihao Cao ◽  
Hui Wang
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Matrix Material ◽  
Melting Process ◽  
Melting Time ◽  
Equivalent Thermal Conductivity ◽  
Melting Front ◽  
Conductivity Model ◽  
Thermal Conductivity Model

Spherically encapsulated phase change materials (PCMs) are extensively incorporated into matrix material to form composite latent heat storage system for the purposes of saving energy, reducing PCM cost and decreasing space occupation. Although the melting of PCM sphere has been studied comprehensively by experimental and numerical methods, it is still challenging to quantitatively depict the contribution of complex natural convection (NC) to the melting process in a practically simple and acceptable way. To tackle this, a new effective thermal conductivity model is proposed in this work by focusing on the total melting time (TMT) of PCM, instead of tracking the complex evolution of solid–liquid interface. Firstly, the experiment and finite element simulation of the constrained and unconstrained meltings of paraffin sphere are conducted to provide a deep understanding of the NC-driven melting mechanism and exhibit the difference of melting process. Then the dependence of NC on the particle size and heating temperature is numerically investigated for the unconstrained melting which is closer to the real-life physics than the constrained melting. Subsequently, the contribution of NC to the TMT is approximately represented by a simple effective thermal conductivity correlation, through which the melting process of PCM is simplified to involve heat conduction only. The effectiveness of the equivalent thermal conductivity model is demonstrated by rigorous numerical analysis involving NC-driven melting. By addressing the TMT, the present correlation thoroughly avoids tracking the complex evolution of melting front and would bring great convenience to engineering applications.

scholarly journals Numerical Study of Latent Heat Thermal Energy Storage Enhancement by Nano-PCM in Aluminum Foam

Inventions ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 76 ◽  
Author(s):  
Bernardo Buonomo ◽  
Anna di Pasqua ◽  
Davide Ercole ◽  
Oronzio Manca
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Metal Foam ◽  
Storage System ◽  
Melting Time ◽  
Change Material

Thermal storage system (TES) with phase change material (PCM) is an important device to store thermal energy. It works as a thermal buffer to reconcile the supply energy with the energy demand. It has a wide application field, especially for solar thermal energy storage. The main drawback is the low value of thermal conductivity of the PCM making the system useless for thermal engineering applications. A way to resolve this problem is to combine the PCM with a highly conductive material like metal foam and/or nanoparticles. In this paper a numerical investigation on the metal foam effects in a latent heat thermal energy storage system, based on a phase change material with nanoparticles (nano-PCM), is accomplished. The modelled TES is a typical 70 L water tank filled with nano-PCM with pipes to transfer thermal energy from a fluid to the nano-PCM. The PCM is a pure paraffin wax and the nanoparticles are in aluminum oxide. The metal foam is made of aluminum with assigned values of porosity. The enthalpy-porosity theory is employed to simulate the phase change of the nano-PCM and the metal foam is modelled as a porous media. Numerical simulations are carried out using the Ansys Fluent code. The results are shown in terms of melting time, temperature at varying of time, and total amount of stored energy.

Numerical Simulation of Solar Ground-Source Heat Pump with Latent Heat Storage

2010 ◽  
Vol 129-131 ◽  
pp. 1069-1073 ◽  
Author(s):  
Fang Wang ◽  
Zhi Long Liu ◽  
Zhong Jian Li ◽  
Mao Yu Zheng
Keyword(s):  
Experimental Data ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Pump ◽  
Heat Storage ◽  
Numerical Results ◽  
Outlet Temperature ◽  
Ground Source Heat Pump ◽  
Latent Heat Storage ◽  
Ground Source

Solar ground-source heat pump (SGSHP) system is unsteady when used to heating. Latent heat storage tank (LHST) was used appropriately in which phase change material (PCM) - CaCl2•6H2O was encapsulated in plastic kegs setting on the serpentine coil. PCM which was as controlling unit of the phase change heat transfer model were solved numerically by an enthalpy-based finite differences method and was validated by experimental data. In order to reflect the effect of the system, two days were chosen to compare the numerical results with experimental data. Inlet and outlet temperature of the water in the LHST, temperature of PCM and storage & emission heat of LHST were measured. The trends of the variation of numerical results and experimental data were in close agreement. Numerical results can reflect the operation mode of the system very well.

Nano-Phase Change Materials for Electronics Cooling Applications

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Laura Colla ◽  
Davide Ercole ◽  
Laura Fedele ◽  
Simone Mancin ◽  
Oronzio Manca ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Phase Change ◽  
Specific Heat ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Melting Time ◽  
Numerical Comparison ◽  
Al2o3 Nanoparticles ◽  
Paraffin Waxes

The present work aims at investigating a new challenging use of aluminum oxide (Al2O3) nanoparticles to enhance the thermal properties (thermal conductivity, specific heat, and latent heat) of pure paraffin waxes to obtain a new class of phase change materials (PCMs), the so-called nano-PCMs. The nano-PCMs were obtained by seeding 0.5 and 1.0 wt  % of Al2O3 nanoparticles in two paraffin waxes having melting temperatures of 45 and 55 °C, respectively. The thermophysical properties such as specific heat, latent heat, and thermal conductivity were then measured to understand the effects of the nanoparticles on the thermal properties of both the solid and liquid PCMs. Furthermore, a numerical comparison between the use of the pure paraffin waxes and the nano-PCMs obtained in a typical electronics passive cooling device was developed and implemented. A numerical model is accomplished to simulate the heat transfer inside the cavity either with PCM or nano-PCM. Numerical simulations were carried out using the ansys-fluent 15.0 code. Results in terms of solid and liquid phase fractions and temperatures and melting time were reported and discussed. They showed that the nano-PCMs determine a delay in the melting process with respect to the pure PCMs.

scholarly journals Numerical investigation on latent thermal energy storage in shell and corrugated internal tube with PCM and metal foam

2021 ◽  
Vol 312 ◽  
pp. 03003
Author(s):  
Bernardo Buonomo ◽  
Francescantonio Di Somma ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Renato Elpidio Plomitallo
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Numerical Investigation ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Metal Foam ◽  
Internal Surface ◽  
Paraffin Wax ◽  
Melting Time

A numerical investigation on Latent Heat Thermal Energy Storage System (LHTESS) based on an aluminum foam totally filled with phase change material (PCM) is accomplished. The PCM used is a pure paraffin wax with melting over a range of temperature and a high latent heat of fusion. The LHTESS geometry under investigation is a vertical shell and tube. The corrugated internal surface of the hollow cylinder is assumed at a constant temperature above the PCM melting temperature. The other external surfaces are assumed adiabatic. The paraffin wax phase change process is modelled with the enthalpy-porosity theory, while the metal foam is considered as a porous media obeying to the Darcy-Forchheimer law. Local thermal non-equilibrium (LTNE) model is assumed to analyze the heat transfer in the metal foam. The governing equations are solved employing the Ansys-Fluent code. The numerical simulations results, reported as a function of time, and concerning the LHTESS charging phase, are compared in terms of melting time, average temperature and energy storage rate. The corrugated internal surface effect is analyzed with respect to the wavelength and wave amplitude of the corrugation.

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