Nano-enhanced phase change material for thermal comfort at skull and environment interface in riding helmets: An experimental investigation

Abstract

In arid climes, the thermal discomfort experienced by motorcycle riders affects their physical and mental wellbeing. This paper proposes a novel approach to cool the interior region of helmets using nano-enhanced organic Phase Change Material (PCM). The solid-solid phase change of organic Neopentylglycol (NPG) PCM, having a solid–solid latent heat of 98 kJ/kg is used in this work. Its phase transition temperature and thermal conductivity are respectively between 39 °C - 47 °C and 0.1–0.15 W/m-K. To enhance the thermal conductivity of organic NPG, it is added with CuO, Al2O3, and TiO2 nanoparticles in 0.1% by mass. The Pure and nano-enhanced samples are initially heated up to 100 cycles. The characterization processes namely the Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) are used to analyse its thermal characteristics, thermal and chemical stoutness respectively. The DSC test result shows that for NPG + 0.1% CuO, NPG + 0.1% Al2O3, NPG + 0.1% TiO2, and pure NPG samples, the respective solid-solid transition latent heats are 92.22 kJ/kg, 91.25 kJ/kg, 90.05 kJ/kg, and 94 kJ/kg. The transition peaks for the aforesaid samples are 43.4 °C, 43.8 °C, 42.9 °C, and 43.7 °C. After 100 thermal cycles, the decrease in the solid-solid transition latent heat is 3.06%, 3.23%, 3.27%, and 2.78% respectively. The TGA and FTIR results show that the thermal and chemical stability of NPG are not significantly affected, either by nanoparticle addition or thermal cycling. At the later stage, the variation in heat conductivity and specific heat capacity are evaluated by the Temperature – history (T-history) method. The result reveals that the thermal conductivities of nano-enhanced test samples (0.1% CuO, 0.1% Al2O3, and 0.1% TiO2) have increased by 14.67%, 11.92%, and 8.26% respectively. Among all the samples, NPG + 0.1% CuO has exhibited more promising results than pure and other nano-enhanced NPG samples. The interior temperature of two identical helmets, one made with 0.1% CuO blended NPG and the other without PCM, have been experimentally analyzed. The initiation of solid-solid transition of NPG has reduced the interior surface temperature by approximately 20% than the latter and thus, the nano-enhanced PCM incorporated helmet can maintain the comfort level for a sufficiently long period.