An Experimental Investigation of Constrained Melting Heat Transfer of Nano-Enhanced Phase Change Materials in a Horizontal Cylindrical Capsule Using Thermochromic Liquid Crystal Thermography

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Nan Hu ◽  
Zi-Rui Li ◽  
Run-Hui Zhang ◽  
Jia Liu ◽  
Li-Wu Fan
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Natural Convection ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermochromic Liquid Crystal ◽  
Melting Front ◽  
Melting Heat ◽  
Melting Heat Transfer ◽  
Imaging Results

Abstract The constrained melting of nano-enhanced phase change materials (NePCM) in a horizontal cylindrical capsule was investigated via the utilization of thermochromic liquid crystal (TLC) technique for tracking the invisible phase interfaces. A parametric study was carried out by varying both the loading of NePCM (i.e., 0 wt %, 1 wt %, and 3 wt %) and the wall superheat (at 10 °C and 30 °C), leading to a total of six cases. Numerical simulations, based on the enthalpy-porosity method, were also performed to reveal the evolutions of temperature and convective flow fields during melting. It was first shown that the numerically predicted melting front evolutions are in good agreement with the TLC imaging results. A comparison among the six cases indicated that there is a similar melting pattern that heat conduction dominates the initial stage of melting and natural convection then takes over to play a more important role when melting proceeds. With the TLC-assisted reconstruction of the melting fronts, the instantaneous melting and heat storage rates were estimated, and melting was clearly found to slow down with increasing the loading of NePCM, as a result of the dramatically increased viscosity that deteriorates the contribution of natural convection to melting heat transfer.

A Novel Indirect Visualization Method for Studying the Melting Heat Transfer of Nano-Enhanced Phase Change Materials Using Thermochromic Liquid Crystal Thermography

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Nan Hu ◽  
Zi-Rui Li ◽  
Run-Hui Zhang ◽  
Li-Wu Fan
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Phase Change ◽  
Phase Change Materials ◽  
Phase Interface ◽  
Classical Problem ◽  
Dominant Mode ◽  
Thermochromic Liquid Crystal ◽  
Melting Heat ◽  
Melting Heat Transfer

Abstract In order to give more sights into the melting (and solidification) heat transfer processes of nano-enhanced phase change material (NePCM) with invisible phase interfaces, a novel indirect method for tracking the phase interface by thermochromic liquid crystal (TLC) thermography is proposed. As an example case to demonstrate the applicability of the proposed method, the classical problem of melting heat transfer in a differentially heated rectangular cavity was revisited in the presence of NePCM of various loadings. A narrowband TLC was selected and calibrated carefully to build the hue–temperature relationship prior to being applied in the melting experiments. For validation purpose, the case of an unloaded NePCM, with a clear visible phase interface, was tested via combined direct and indirect observations. It was shown that this TLC method can easily and accurately capture the dynamic motions of the phase interface during melting. Based on the shape evolutions of the phase interface, it was concluded that for the NePCM sample with a higher loading (and hence a much greater viscosity), heat conduction becomes the dominant mode of heat transfer during melting as a result of the significantly deteriorated natural convection effect. This gives an intuitive confirmation of the hypothesis made in previous studies that were conducted using volume-average-based indirect methods.

scholarly journals CuO–Water Nanofluid Magnetohydrodynamic Natural Convection inside a Sinusoidal Annulus in Presence of Melting Heat Transfer

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sheikholeslami ◽  
R. Ellahi ◽  
C. Fetecau
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Melting Heat ◽  
Melting Heat Transfer ◽  
Limiting Case ◽  
Good Agreement ◽  
Melting Parameter

Impact of nanofluid natural convection due to magnetic field in existence of melting heat transfer is simulated using CVFEM in this research. KKL model is taken into account to obtain properties of CuO–H2O nanofluid. Roles of melting parameter (δ), CuO–H2O volume fraction (ϕ), Hartmann number (Ha), and Rayleigh (Ra) number are depicted in outputs. Results depict that temperature gradient improves with rise of Rayleigh number and melting parameter. Nusselt number detracts with rise of Ha. At the end, a comparison as a limiting case of the considered problem with the existing studies is made and found in good agreement.

Natural Convection in an Enclosure With Blend of Micro Encapsulated Phase Change Materials

2013 ◽  
Author(s):  
Yasmin Khakpour ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Thermal Expansion ◽  
Natural Convection ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Numerical Study ◽  
Pure Water ◽  
Operating Conditions ◽  
Effective Density

This numerical study investigates the effect of using a blend of micro-encapsulated phase change materials (MEPCMs) on the heat transfer characteristics of a liquid in a rectangular enclosure driven by natural convection. A comparison has been made between the cases of using single component MEPCM slurry and a blend of two-component MEPCM slurry. The natural convection is generated by the temperature difference between two vertical walls of the enclosure maintained at constant temperatures. Each of the two phase change materials store latent heat at a specific range of temperatures. During phase change of the PCM, the effective density of the slurry varies. This results in thermal expansion and hence a buoyancy driven flow. The effects of MEPCM concentration in the slurry and changes in the operating conditions such as the wall temperatures compared to that of pure water have been studied. The MEPCM latent heat and the increased volumetric thermal expansion coefficient during phase change of the MEPCM play a major role in this heat transfer augmentation.

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