Measurement of thermal conductivity of graphene–water nanofluid at below and above ambient temperatures

The present paper deals with the design, development and the measurement of thermal conductivity of graphene–water nanofluid using a transient hot wire technique at temperatures below and above ambient conditions ranging from 10 °C to 50 °C. The equipment is designed to measure the thermal conductivity using a single platinum wire of diameter 50 μm and 100 mm length. The platinum micro-wire acts both as a temperature sensor and heating element. Low volume concentrations (0.05, 0.1 and 0.15%) of graphene, having the size less than 100 nm, dispersed in 100 ml of water with SDBS (sodium dodecyl benzene sulfonate) as surfactant, for prolonged stability, is used in the present study. The results showed an enhancement in the thermal conductivity of 37.2% for 0.15% volume concentration of graphene at 50 °C when compared with that of the water at the same temperature. An interesting observation from this study is that the average thermal conductivity enhancement percentage with the increase in volume concentration (say from 0.05% to 0.15%) is found to be 3.3% higher when compared with that of the average enhancement with the increase in temperature from 10 °C to 50 °C.