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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

NUMERICAL STUDY OF NANO-ENHANCED PCMS: ARE THEY WORTH IT?

DOI: 10.1615/TFESC1.mph.012946
pages 1951-1964

Dominic Groulx
Mechanical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 4R2


KEY WORDS: Phase Change Heat Transfer, Numerical Modeling, Conductivity Enhancement, Nano-Particles

Abstract

There has been a push in recent years for development of nano-enhanced phase change materials (NEPCMs) to counteract the inherent very small thermal conductivity of most PCM used today in applications such as thermal energy storage and temperature control of various systems (PV panels, electronic systems, etc). All this work still has not answered the following simple question: is spending all these efforts and research funding towards the development of NEPCMs worth it? In other words, is increasing the very low conductivity of such materials by 50%, even 100%, enough to make a difference in thermal storage systems? As engineers, it is primordial to properly answer these questions in order to determine which avenue of research should be pursued when it comes to NEPCMs. This research paper presents a numerical study, using a model in COMSOL Multiphysics which was calibrated and validated from experimental work, to study the melting and solidification behavior of a NEPCM presented in the literature versus its base PCM. By performing a complete energy-analysis (energy stored - recovered, energy transfer rates) and comparing the results, it is possible to shed light on the overall benefits of using NEPCMs. This study concludes that during charging (melting), although melting more slowly, a base PCM still store energy faster than the NEPCM, and ultimately store more total energy. This comes from the fact that natural convection plays the dominant role during melting, which mitigates the impact of the increased thermal conductivity of the NEPCM. During discharging (solidification), the NEPCM solidifies and recovers energy much faster than the base PCM, clearly pointing to the advantage of having a higher thermal conductivity. However, using a simple and much less expensive fin system easily fixes the short-coming of the base PCM leading to fast energy recovery. The main conclusion drawn from this work is that NEPCMs, of the type studied in this work, do not present enough of a gain to justify their utilization compared to much less expensive base PCMs.

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