Overall heat transfer coefficient improvement of an automobile radiator with graphene based suspensions

Abstract

In the present work, we report the enhancement in overall heat transfer coefficient of an automobile radiator using graphene nanoplatelets based nanofluid as the coolant. Water-ethylene glycol mixture (70:30 by volume) was used as the base fluid and stable nanofluids were synthesized by non-covalent functionalization method with volume concentrations of graphene nanoplatelets varying from 0.1% to 0.5%. Experiments were performed in an automobile radiator for varying nanofluid mass flow rates viz. 12.5g/s, 25g/s, 37.5g/s, 50g/s, 62.5g/s and two nanofluid inlet temperatures viz. 35°C, 45°C and air velocity. For each condition the ambient air velocity was varied from 1m/s to 5m/s in steps of 1m/s. The convective heat transfer coefficient of nanofluid and overall heat transfer coefficient are found to increase with respect to mass flow rate, inlet temperature of nanofluid and graphene nanoplatelets loading. The improvement in convective heat transfer coefficient of nanofluid play a significant role in the enhancement of overall heat transfer coefficient. The maximum enhancement in OHTC with respect to concentration is found to be ∼104% at 35°C while it is found to be ∼81% at 45°C for 0.5vol%, 62.5g/s flow rate and 5m/s air velocity. Further, the pressure drop of nanofluids increases with increase in mass flow rate and graphene loading. The increase in pressure drop is significantly influenced by the mass flow rate than by graphene nanoplatelets loading.