Thermophysical Properties of POLWAX LTP ST Paraffin Doped with or without Carbon Nanotubes or Silver Nanowires and Passive Cooling of a High-Power LED Panel

Janusz Zmywaczyk (), Piotr Zbińkowski and Piotr Koniorczyk
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Janusz Zmywaczyk: Faculty of Mechatronics, Armament and Aerospace, Military University of Technology (MUT), Gen. S. Kaliskiego Street No 2, 00-908 Warsaw, Poland
Piotr Zbińkowski: Faculty of Physics, Institute of Experimental Physics, University of Warsaw, Ludwika Pasteura Street No 5, 02-093 Warsaw, Poland
Piotr Koniorczyk: Faculty of Mechatronics, Armament and Aerospace, Military University of Technology (MUT), Gen. S. Kaliskiego Street No 2, 00-908 Warsaw, Poland

Energies, 2023, vol. 16, issue 16, 1-17

Abstract: Commercially available paraffin wax LTP ST, manufactured in Poland by POLWAX, was used as a phase change material (PCM) for passive cooling of an LED panel containing 28 high power light emitting diodes (LEDs). Paraffin wax LTP ST of density ρ = 930 kg·m −3 at room temperature (RT) was chosen over other POLWAX waxes (LUXOLINA, LUXOLINA-ST, and LTP 56-20) because of its melting point range (44.5–55.4 °C), relatively high latent heat of fusion ΔH = 218.8 J·g −1 , high specific heat Cp = 2.11 J·g −1 K −1 and thermal conductivity k = 0.233 Wm −1 K −1 at 0 °C. The thermophysical properties were studied in samples of pure LTP ST paraffin and doped with multi-walled carbon nanotubes (1.99, 3.49, 5.35, and 10.49 wt%, MWCNTs) or silver nanowires (0.26, 0.32, 1.06, 2.10, and 7.35 wt%, SNWs). Analysis of the thermal effects of doped samples showed a relative increase in the degree of subcooling, averaging 100% for MWCNT and 46% for SNW, a relative 15÷25% decrease in enthalpy of melting for MWCNT and 14÷16% for SNW. A 44% increase in thermal conductivity was found for the sample containing 5.35 wt% MWCNTs and a 91% increase for 1.06 wt% SNW. The results of cooling efficiency tests for three types of developed heat sinks fabricated of AW-2017A aluminum alloy are presented, i.e., (a) full system without PCM filling, (b) system with PCM chamber without intracellular ribs, (c) and system with PCM chamber with intracellular fins.

Keywords: paraffin wax LTP ST; passive cooling; panel LEDs; phase change material PCM; heat sinks; carbon nanotubes; silver nanowires (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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