Phase Change Heat Transfer Enhancement Using Copper Porous Foam

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
Ali Siahpush ◽  
James O’Brien ◽  
John Crepeau
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Storage System ◽  
Vertical Cylinder ◽  
Energy Storage System ◽  
Scaling Analysis ◽  
Interface Position ◽  
Solid Liquid

A detailed experimental and analytical study has been performed to evaluate how copper porous foam (CPF) enhances the heat transfer performance in a cylindrical solid/liquid phase change thermal energy storage system. The CPF used in this study had a 95% porosity and the phase change material (PCM) was 99% pure eicosane. The PCM and CPF were contained in a vertical cylinder where the temperature at its radial boundary was held constant, allowing both inward freezing and melting of the PCM. Detailed quantitative time-dependent volumetric temperature distributions and melt/freeze front motion and shape data were obtained. As the material changed phase, a thermal resistance layer built up, resulting in a reduced heat transfer rate between the surface of the container and the phase change front. In the freezing analysis, we analytically determined the effective thermal conductivity of the combined PCM/CPF system and the results compared well to the experimental values. The CPF increased the effective thermal conductivity from 0.423W∕mKto3.06W∕mK. For the melting studies, we employed a heat transfer scaling analysis to model the system and develop heat transfer correlations. The scaling analysis predictions closely matched the experimental data of the solid/liquid interface position and Nusselt number.

scholarly journals Scale Analysis and Experimental Results of a Solid/Liquid Phase-Change Thermal Energy Storage System

2014 ◽  
Author(s):  
Ali Siahpush ◽  
James O’Brien ◽  
John Crepeau ◽  
Piyush Sabharwall
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Liquid Phase ◽  
Phase Change ◽  
Thermal Energy ◽  
Storage System ◽  
Energy Storage System ◽  
Scale Analysis ◽  
Thermal Energy Storage System ◽  
Solid Liquid

A detailed experimental study has been carried out to evaluate the heat transfer performance of a solid/liquid phase-change thermal energy storage system. The phase-change material (PCM) and metal foam are contained in a vertically oriented test cylinder that is cooled or heated at its outside boundary, resulting in radially inward melting, respectively. Detailed quantitative time-dependent volumetric temperature distributions and melt-front motion and shape data were obtained. As the PCM melts, the interface moves away from the surface of the heat source/sink, and a thermal resistance layer is built up, resulting in a reduced heat transfer rate and/or increased temperature difference between the system to be cooled (or heated) and the PCM. The phase-change medium was 99% pure eicosane, with a melting temperature of 36.5°C. Results have been generalized to apply to any low-Stefan number PCM. A heat transfer scale analysis was used in order to help in interpretation of the data and development of heat transfer correlations. In the scale analysis, conduction heat transfer in the solid and natural convection heat transfer in liquid were considered. Comparison of experimental data with scale-analysis predictions of the solid-liquid interface position and temperature distribution was performed.

Simple Heat Transfer Experiment to Evaluate the Solid/Liquid Phase Change Thermal Energy Storage System

2015 ◽  
Author(s):  
Ali Siahpush ◽  
James O’Brien ◽  
John Crepeau
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Liquid Phase ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Energy Storage System ◽  
Thermal Energy Storage System ◽  
Solid Liquid

A detailed experimental freezing study, designed for undergraduate students, has been carried out to evaluate the heat transfer performance of a solid/liquid phase-change thermal energy storage system. The test vessel system, experimental procedure and results, and analytical solutions are discussed. The phase-change material (PCM) is contained in a vertically oriented test cylinder that is cooled at its outside boundary, resulting in radially inward freezing. Detailed quantitative time-dependent volumetric temperature distributions and freeze-front motion and shape data were experimentally obtained. To fully understand the behavior of the eicosane, four freezing tests were performed with different temperature set points as low as 10°C. In the analysis, results of a test in which molten eicosane, initially at 50°C, was solidified and brought to a final temperature of 10°C are presented. In the freezing case study, a mathematical model based on a one-dimensional analysis, which considered heat conduction as the only mode of heat transfer was developed. The phase-change medium, 99% pure eicosane (C20H42) was chosen as the PCM. Eicosane is desirable because its fusion temperature is just slightly higher than ambient temperature (36.5°C), which is convenient for phase-change experimentation. Low-temperature heating can be used to melt the PCM and ambient-temperature cooling can be used to re-freeze it. To evaluate the inward radius of fusion, several analytical and experimental approaches were considered. These approaches were (1) experimental method; (2) conduction model; (3) integral method; and (4) cumulative heat transfer method. Comparison of these methods reveals excellent agreement. In most cases, the heat transfer estimated from the freezing-front analysis was slightly higher than the heat transfer evaluated from the time-series data. The largest discrepancy occurs at fifty minutes into the experiment (10.7%).

Figure of Merit-Based Optimization Approach of Phase Change Material-based Composites for Portable Electronics Using Simplified Model

2021 ◽  
Author(s):  
Ayushman Singh ◽  
Srikanth Rangarajan ◽  
Leila Choobineh ◽  
Bahgat Sammakia
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Figure Of Merit ◽  
Volume Fraction ◽  
Simplified Model ◽  
Transient Temperature ◽  
Change Material

Abstract This work presents an approach to optimally designing a composite with thermal conductivity enhancers (TCEs) infiltrated with phase change material (PCM) based on figure of merit (FOM) for thermal management of portable electronic devices. The FOM defines the balance between effective thermal conductivity and energy storage capacity. In present study, TCEs are in the form of a honeycomb structure. TCEs are often used in conjunction with PCM to enhance the conductivity of the composite medium. Under constrained composite volume, the higher volume fraction of TCEs improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. The present work arrives at the optimal design of composite for electronic cooling by maximizing the FOM to resolve the stated trade-off. In this study, the total volume of the composite and the interfacial heat transfer area between the PCM and TCE are constrained for all design points. A benchmarked two-dimensional direct CFD model was employed to investigate the thermal performance of the PCM and TCE composite. Furthermore, assuming conduction-dominated heat transfer in the composite, a simplified effective numerical model that solves the single energy equation with the effective properties of the PCM and TCE has been developed. The effective thermal conductivity of the composite is obtained by minimizing the error between the transient temperature gradient of direct and simplified model by iteratively varying the effective thermal conductivity. The FOM is maximized to find the optimal volume fraction for the present design.

scholarly journals Enhanced Thermal Characteristics of NG Based Acetamide Composites

2019 ◽  
Vol 8 (10) ◽  
pp. 4227-4231 ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Storage System ◽  
Thermal Characteristics ◽  
Energy Storage System ◽  
Melting Time

Fatty acids are a distinguished category of phase change materials (PCM). However, their inferior thermal conductivity value restricts their potential for thermal energy storage system. Carbonaceous nanomaterials have emerged as promising thermal conductivity enhancer materials for organic PCMs. The present study focuses on preparing a novel PCM nanocomposite comprising of small amount of nanographite (NG) in molten acetamide, an organic PCM, for elevation of the thermal characteristics and examining the trend of the nanocomposite through the course of charging / discharging process. These PCM-nanocomposites are prepared by dispersing NG in molten acetamide with weight fractions of 0.1, 0.2, 0.3, 0.4 and 0.5 %. The scanning electronic microscopic (SEM) analysis was conducted for the characterization of PCM nanocomposite. The energy storage behaviour of the prepared nanocomposites were analyzed with the help of differential scanning calorimeter instruments, which showed that there is no observable variation in the melting point of the nanocomposite, and a decline in the latent heat values. Furthermore, thermal conductivity trend of the nanocomposites caused by NG addition was investigated, which indicated enhancement of thermal conductivity with increasing NG concentration. Further, nanocomposites with a 0.4 wt. % of NG, displayed appreciable increase in rate of heat transfer, reducing melting time and solidification time by 48 and 47 %, respectively. The prepared PCM nanocomposites displayed superior heat transfer trend, permitting substantial thermal energy storage.

The Experimental Research and Numerical Simulation on Thermal Properties of Molten Salt at Melting Point

2009 ◽  
Author(s):  
Yannan Liang ◽  
Jiemin Zhou ◽  
Ying Yang ◽  
Ye Wu ◽  
Yanyan He
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Phase Change ◽  
Molten Salts ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Phase Interface ◽  
Measuring System ◽  
Solid Liquid

The use of phase-change materials for latent heat storage is a new type of environmentally-friendly energy-saving technologies. Molten salts, one kind of phase-change materials, which have high latent heats, and whose phase transition temperatures match the high temperatures of heat engines, are the most widely used high-temperature phase-change heat storage materials. However, the heat transfer at solid/liquid phase interface belongs to Micro/Nanoscale Heat transfer, lots of the thermal properties of molten salt at melting point is difficult to test. In this investigation, based on the theory that the thermal conductivity can be determined by measuring the speed of the propagation of the solid/liquid phase interface during phase change, a set of system is developed to investigate the thermal conductivity of molten salts at liquid/solid phase transformation point. Meanwhile, mathematical calculation is applied to intuitively simulate the melting and solidifying process in the phase change chamber, by which the error could be analyzed and partly corrected and the result precision could also be increased. And a series of verification experiments have been performed to estimate the precision and the applicability of the measuring system to evaluate the feasibility of the method and measuring system. This research will pave the way to the follow-on research on heat storage at high temperature in industry.

Investigation of Using Dispersed Particle and Branching Heat Exchnager in Medium Temperature Thermal Energy Storage System to Achieve Maximum Utilization of Solar Power

2013 ◽  
Author(s):  
A. M. M. G. Hasib ◽  
Rambod Rayegan ◽  
Yong X. Tao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Power Generation ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Energy Storage System ◽  
Medium Temperature ◽  
Change Material

Maximum utilization of solar energy is very critical to achieve, because a significant portion of solar energy is lost in the form of heat. In that case Thermal Energy Storage (TES) can play a significant role by capturing the energy in the form of heat and later on can be used as a backup source of energy for utilizing it in critical time. On the other side, from the view point of conservation of energy, energy cannot be created or destroyed, but surprisingly a significant amount of energy cannot be utilized due to the instantaneous nature of conventional power generation. So storing Energy is the most unique idea that can act as a strong backup for the instantaneous nature of power generation as it not only adds up to the power generation capacity but also serves to be the most reliable medium of supplying power when the energy demand is at peak. In the authors’ previous work a phase change material (molten solar salt comprised of 60% NaNO3+40%KNO3) and a system design for thermal energy storage (TES) system integrated with a solar Organic Rankine Cycle (ORC) has been proposed. The associated research problems investigated for phase change material (PCM) are the low thermal conductivity and low rate of heat transfer from heat transfer fluid to PCM. In this study a detailed numerical modeling of the proposed design using MATLAB code and the relevant calculation and results are discussed. The numerical model is based on 1-D finite difference explicit technique using the fixed grid enthalpy method. To overcome the research problem highly conductive nano-particle graphite is used to enhance the effective thermal conductivity of the PCM material in theoretical calculation. In the later part of the study results from the numerical computation have been utilized to demonstrate a comparison between a conventional heating system (with a simple single tube as a heat exchanger) and a branching heat exchanger in PCM thermal energy storage system using NTU-Effectiveness method. The comparison results show a significant amount of improvement using branching network and mixing nano-particle in terms of heat transfer, thermal conductivity enhancement, charging time minimization and pressure drop decrease. The results of this study can convince us that the proposed medium temperature TES system coupled with solar ORC can be a stepping-stone for energy efficient and sustainable future in small-scale power generation as the system proves to be better in terms of enhanced heat transfer, increased thermal conductivity and overall sustainability.

Characterization of Thermal Properties and Heat Transfer Behavior of Microencapsulated Phase Change Material Slurry and Multiwall Carbon Nanotubes in Aqueous Suspension

2007 ◽  
Author(s):  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Curt Thies ◽  
Guillermo Soriano ◽  
Paritosh Garg
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Microencapsulated Phase Change Material ◽  
Change Material

In the last decade, microencapsulated phase change material (MPCM) slurries have been proposed and studied as novel coolants for heat transfer applications. Such applications include electronics cooling, and secondary coolants in air conditioning systems among others. Experiments have shown that MPCM’s increase the overall thermal capacity of thermal systems by taking advantage of the phase change material’s latent heat of fusion. However, research has also shown that the overall heat transfer coefficient is diminished due to a reduction in the effective thermal conductivity and increased viscosity of the slurry. For this reason, there is an urgent need to modify the content of microcapsules containing phase change material to increase their effective thermal conductivity and the overall heat transport process. Our solution consists of increasing the thermal conductivity of MPCM by adding carbon nanotubes to the shell and core of the microcapsules. Carbon nanotubes have shown to increase the thermal conductivity of liquids by 40% or more in recent experiments. In this paper, MPCM slurry containing octadecane as phase change material and multi-wall carbon nanotubes (MWCNTs) embedded in the capsule material and core are compared with pure water as heat transfer fluid. Thermal and physical properties of MPCM slurry containing carbon nanotubes were determined using a differential scanning calorimeter and concentric viscometer, respectively. Experimental convective heat transfer coefficient data for MWCNT aqueous suspensions under laminar flow and constant heat flux were determined using a bench-top heat transfer loop. Experimental heat transfer results are presented.

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