• Energy Research

AbstractIn high-energy-demand regions, such as the Arctic, the building sector is focused on reducing the carbon footprint and mitigating environmental impact. To achieve this, phase change materials (PCMs) are being investigated for thermal energy storage due to their high latent heat of fusion. However, their limited applications arise from poor thermal conductivity. In addressing this issue, the research delves into the preparation and characterization of nano-PCMs. These materials, synthesized in a laboratory setting, exhibit enhanced thermal performance compared to pure PCMs, attributed to the incorporation of nanoparticles in the material composition. Therefore, in the study, three paraffins with different melting temperatures (10, 15 and 18 °C) are modified by incorporating titanium oxide at various concentrations (0.05, 0.1, 0.2 and 0.5 mass%). Thermal conductivity and latent heat capacity measurements were undertaken using a thermal conductivity measuring apparatus and differential scanning calorimetry, respectively. The aim was to evaluate the enhanced performance of the modified PCMs in comparison with pure PCMs and to assess their suitability for cold climate regions. Results showed that nanoparticle incorporation increased thermal conductivity by up to 37%, albeit with a slight reduction in latent heat capacity of up to 12%. Among the samples, RT18 exhibited the most significant improvement in thermal conductivity, while RT10 experienced a minor decrease in enthalpy values. Ultimately, RT10 was identified as the optimal PCM option for cold climates, as its phase change temperature range aligns with the outdoor temperatures in the Arctic.

Abstract Phase change material (PCM) has been extensively used for their thermal management but due to low conductivity that hinders the performance of a system. Since heat pipe and porous materials both have high thermal conductivities, they can be used to form hybrid system with PCM which significantly enhance the heat transfer capability of PCM. In current research of heat pipe, copper foam (pore density 40PPI and porosity 93%) and PCM based heat sinks are used to inspect the thermal performance of heat sink with respect to time by varying heat fluxes. ‘‘RT-35HC” PCM, copper foam and gravity assisted heat pipe with and without cooling fan are used in experimental investigation. The results showed after 6000 s when charging ends hybrid cooling (Foam-PCM-HP) with fan have maximum temperature reduction i.e. 47%, 51% and 54% at heat flux of 2, 2.5 and 3 kW/m2 respectively. Similarly, for discharging hybrid cooling with fan showed excellent cooling results at all heat fluxes.

Organic phase change materials are extensively researched for passive cooling of electronic components due to the high heat of fusion, however, owing to the issue of thermal conductivity, it is difficult to improve the thermal performance of electronic components. However, the effective thermal performance of modern electronic devices is becoming popular due to thermal constraints of the circuit's non-uniform temperature distribution and high heating power generation. Thus, nanomaterials incorporated into phase change materials (PCMs) to improve thermal conductivity, which aids in heat removal and sustains significant heat sink operational performance for extended periods of time. In current research work, at heating powers of (10–30 W), the thermal performance outcome of three heat sink -configurations such as unfinned heat sink, circular pin-finned heat sink and metallic foam integrated heat sink were investigated with several alumina nanomaterials mass concentrations (0.15, 0.20 and 0.25 wt%) incorporated in phase change materials (for example RT-70HC). All three heat sinks revealed lower base temperature with the addition of alumina NePCM (αRT-70HC) phase change materials in their internal cavity compared to the empty unfinned heat sink. The findings showed good performance of metallic foam integrated heat sink in lowering the temperature & increasing safe functional time at two distinct temperatures. The largest decrease in temperature was found to be 35.76% and the largest growth in maximum functional time was 400% for metallic foam integrated heat sink. Therefore, using alumina nanomaterials in phase change material is recommended to optimize the thermal performance of the passive cooling techniques.

Data availability: Data will be made available on request. Copyright © 2023 The Author(s). Phase change materials (PCMs) are a promising panacea to tackle the intermittency of renewable energy sources, but their thermal performance is limited by low thermal conductivity (TC). This pioneering work investigates the potential of organic PCM-enriched surface-modified and un-modified multi-walled carbon nanotubes (MWCNTs) for low-temperature thermal energy storage (TES) applications. The functionalised and un-functionalised MWCNTs enhanced PCM have demonstrated a TC enhancement of 158 % and 147 %, respectively, at 25 °C. However, the TC value of the unmodified MWCNTs-based PCM dropped by 52.5 % after 48 h at 25 °C, while that of the functionalised MWCNTs-based PCM remained stable. A DSC analysis of up to 200 thermal cycles confirmed that the surface-modified and un-modified MWCNTs had no major effect on the peak melting and cooling temperatures of the nano-enhanced PCMs although a minor decrease of 7.5 % and 7.7 % in the melting and crystallisation enthalpies, respectively, was noticed with the inclusion of functionalised MWCNTs. Moreover, functionalised MWCNTs incorporated PCMs have led to increases in specific heat capacity by 23 % with an optimal melting enthalpy value of 229.7 J/g. In addition, no super-cooling, no phase segregation, and a small phase change temperature were noticed with these nano-enhanced PCMs. Finally, no chemical interaction from nano-PCMs was seen in the FT-IR spectra with the incorporation of both functionalised and un-treated MWCNTs. It is evident that the functionalised MWCNT-based PCM has better thermal stability and it offers a promising alternative for improving thermal storage and management capabilities in buildings, contributing to a sustainable and energy-efficient building design. European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 801604.