Improving hydrothermal performance of a tubular heat exchanger with different types of twisted tapes using graphene nanoplatelets/water nanofluid

A comparative experimental investigation in order to evaluate the hydrothermal characteristics of a heat exchanger tube fitted with varied types of twisted tape is performed using graphene nanoplatelets (GNP) and water nanofluid. The experiment is carried out for three varied weight concentrations (omega = 0.05%, 0.075% and 0.1%) of GNP/water nanofluids flowing in a tube fitted with various twisted tapes of three different twist ratios (x/b = 3, 4 and 5) for the Reynolds number of 6700 -33,200 and a nanofluid flow rate of 5 to 25 lpm. The results showed the heat transfer rate and pressure loss increased with rising Reynolds numbers, a decrease in the twist ratio of tapes, and an increase in nanofluid concentration. The specially designed anti-clockwise clockwise twisted tape (ACCT) insert provides a 67.8% greater heat transfer coefficient than typical twisted tape. The addition of GNP nanoparticles to water has a significant impact on the increase in heat transfer rate. The best hydrothermal performance factors achieved are 2.03, 1.93, and 1.84 for ACCT tape (x/b = 3) fitted tube at Reynolds number of 26,600 for 0.1%, 0.075%, and 0.05% weight concentration of GNP/water nanofluids, respectively. Nusselt number and friction factor correlations are also established in terms of twist ratio, Reynolds number, and nanofluid concentration parameters.