An experimental evaluation of thermal conductivity of colloidal suspension of carbon‑rich fly ash microparticles and diamond‑nano powder (DNP) in Jet‑A fuel

This study investigates the enhancement of thermal conductivity in Jet‑A fuel by dispersing carbon‑based micro/nano materials, specifically Carbon Fly Ash (CFA) and Diamond Nano Powder (DNP). CFA, derived from heavy fuel oil combustion and rich in unburned carbon and inorganic oxides, possesses a porous structure, while DNP is renowned for its high thermal conductivity. Both materials were introduced into Jet‑A fuel to assess their impact on heat‑transfer properties. Colloidal suspensions were stabilized using a two‑step process involving surfactant addition and sonication, with stability lasting between 20 and 60 minutes, depending on particle concentration. Thermal conductivity measurements under controlled heat flux conditions revealed that a 2 wt.% DNP concentration increased thermal conductivity by 2 %, whereas a 3 wt.% CFA concentration resulted in an 8 % improvement, comparable to activated carbon nanoparticles. The significant enhancement by CFA is attributed to its porous structure and trace iron content, making it a promising additive for fuel‑performance improvements. This study highlights the potential of CFA and DNP to enhance thermal properties in Jet‑A fuel, while also identifying challenges in colloidal stability, particularly for DNP.