Application of high surface area graphene for enhanced heat transfer co-efficient – An experimental study

Abstract

Increased heat transmission has contributed significantly to cost and energy savings. The desire for compact gadgets with the finest performance, correct working, and long lifespan is being fuelled by today's scientific and technological advancements. The researchers were able to introduce a fresh kind of fluid with a mixture that was referred to as “Nanofluids” due to their superior thermal transfer capabilities compared to regular fluids. Applications for nanofluids in the electrical and other cooling industries are numerous. In this work, hydrogen exfoliated Graphene of two types i.e. multilayer Graphene designated as L- type and monolayer Graphene designated as A+-type is diffused in pure deionized (DI) water and also in deionized water blended with ammonium hydroxide (NH4OH) to prepare the Graphene-based nanofluid samples. In a concentric-pipe heat exchanger, the prepared nanofluids are utilised to calculate the heat transfer co-efficients. Samples are experimentally investigated to study the outcome of weight concentration and pH on The Heat Transfer Co-efficient (HTC). Results have shown that the HTC is higher for all nanofluid samples than that of water at all the flow rates studied. Six nanofluid samples are prepared with two volume fractions of 0.005% and 0.01%. Three samples were prepared with each of L-type Graphene and A+-type Graphene materials. For sample1 which is prepared by dispersing 0.5 gm of L-type Graphene in 10 L of water, the improvement in combined heat transfer co-efficient observed was 14.5 % over water. For sample 2 prepared by adding a further 50 ml of NH4OH to the sample 1 enhancement over water is observed to be 20.2%. 1 g of L-type graphene is dissolved in ten litres of water to create Sample 3, which has a 24.5% improvement in combined HTC. For the nanofluid samples 4, 5 and 6 prepared with A+-Type Graphene, the corresponding increase in combined heat transfer co-efficient s observed were 44.6 %, 50.2%, and 53.6% respectively. In comparison to L-type samples, nanofluid samples made with A + -type Graphene were shown to provide better thermal performance.