Thermal transport properties enhancement of paraffin via encapsulation into boron nitride nanotube: a molecular dynamics
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Research Letter
Thermal transport properties enhancement of paraffin via encapsulation into boron nitride nanotube: a molecular dynamics study Nastaran Barhemmati-Rajab , Department of Mechanical and Energy Engineering, University of North Texas, Denton, TX 76203, USA Thiruvillamalai Mahadevan and Jincheng Du, Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA Weihuan Zhao, Department of Mechanical and Energy Engineering, University of North Texas, Denton, TX 76203, USA Address all correspondence to Weihuan Zhao at [email protected] (Received 10 April 2020; accepted 16 June 2020)
Abstract This research investigates a novel composite of encapsulated paraffin in boron nitride nanotube (BNNT) which is more thermally and chemically stable than carbon nanotube. This composite can achieve high thermal conductivity and, meanwhile, have thermal energy storage capability for efficient thermal management under extreme conditions. Equilibrium molecular dynamics simulations were conducted to study selfdiffusion coefficient, thermal conductivity, and specific heat of encapsulated paraffin. The simulation results indicated that the self-diffusion coefficient and thermal conductivity of paraffin could be increased by up to 10 and 7 times, respectively, while specific heat was reduced after encapsulating into BNNT.
Nomenclature CP D E J k kB N ri T t V
Constant pressure specific heat (kJ/kg K) Self-diffusion coefficient (m2/s) Total energy (eV) Heat flux (W/m3) Thermal conductivity (W/m K) Boltzmann constant Number of atoms Position vector of ith particle Temperature (K) Time (s) Volume (m3)
Greek symbol δ Difference
Subscripts NPT Constant pressure–constant temperature NVE Microcanonical ensemble
Introduction Paraffin is one of the common organic phase change materials (PCMs), which is widely applied in thermal energy storage.[1–6] It has a wide phase change temperature range, high latent heat of fusion, stable thermal and chemical properties, and lower price compared with metals and molten salts.[1–7] However,
paraffin has low thermal conductivity[5–15] that limits its thermal transport performance. Hence, researches have been conducted to enhance its thermal conductivity values, such as applying nano-suspension techniques.[15–18] Nevertheless, some applications are not suitable to have a device or material directly contact with liquid. Therefore, it is proposing to encapsulate paraffin into nanotubes to overcome this issue when PCM turns into a liquid state. Boron nitride nanotube (BNNT) is getting more and more attentions for various applications nowadays due to its extraordinary properties including large thermal conductivity,[19] which makes it applicable for efficient heat dissipation in electronics operations.[20–24] There have been a lot of studies regarding carbon nanotube (CNT) application in thermal conductivity enhancement of the matrix material, but the recent interests moved to BNNT due to its greater thermal and chemical stability,[19,20] higher specific heat and lighter
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