Water, ethylene glycol and engine oil are commonly used in heat exchanger applications. However, these fluids possess low thermal conductivity. The technology advancement in nanotechnology has enabled nano size particles to be included in a base fluid. This new generation of fluids is known as nanofluids. Producing a stable nanofluid with improved thermal conductivity is a challenging process. In the present study, multiwalled carbon nanotubes (MWCNT) based nanofluids with or without surfactant were investigated for their stability and thermal conductivity. The study indicates that nanofluids with added polyvinylpyrrolidone (PVP) surfactant exhibit better stability than nanofluids without surfactant. About 22.2% thermal conductivity improvement was observed for water containing 0.5wt% of MWCNT and 0.01wt% of PVP surfactant. The thermal conductivity also increases with increase of the MWCNT's weight fraction. It can be concluded that the addition of PVP and MWCNT into base fluid (water) is vital to produce a stable nanofluid with improved thermal conductivity.
Body armour technologists over the years are seeking to develop protective systems which are both effective and lightweight. However these hard armour materials are very expensive and have certain weight constraints. From this point of view, natural fibres and fillers have attracted the attention of researchers due to their low density with high specific strengths, abundance, availability, renewability and being environmental-friendly. This paper reports the potential use of coconut shell powder-epoxy composite (COEX) panel bonded with Twaron CT716 fabric as a hard armour material and the characteristics of its fracture imprints from a specific threat level when subjected to ballistic tests 1 (NIJ Standard 0108.01). It was observed that the imprint patterns on the particulate composite (COEX) could be identified according to effectiveness in impact energy dissipation. COEX/Twaron test panel was found to withstand impact equivalent to NIJ Level IIIA using 9 mm FMJ ammunition but perforated at NIJ Level III of 7.62 mm FMJ bullet impacts. Test results showed that COEX panel do possess shock absorbance characteristics and can be utilised as an armour component in the hard-body armour system. Dependency on Twaron fabric layers as ballistic reinforcements has been reduced up to 3-time with 170 per cent improvement on energy-absorption capabilities when using COEX composite as the frontal component of the armour.
Exp losion fro m an anti-tank mines or imp rovised explosive devices are recognized as one of the lethal threat towards occupants inside an armoured vehicle. The detonation of these threats creates high intensity blast waves that were transmitted to the occupant through vehicle structures and seats. Minimizing the occupant's casualty can be achieved by properly dissipating the shock waves exerted to the vehicle. It is important to distinguish the contributing factors that affectted the behavior of the blast wave so that proper reduction on the shock waves can be achieved. In this paper, three factors such as occupant seating height, charge weight placement and the Hopkinson-Cran z b last scaling were studied using numerical simu lations. Design of experiment (DOE) was utilized to determine the ranks and interactions between each factor fro m the most influential on the results to the least affects towards the results. Fro m the results it was found that the seating position play s a significant ro le in reduction of the shock response towards the finite element dummy model.
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