| Summary: | The wet ball milling method was used and a dispersant (gum Arabic) was added to prepare various concentrations (0.05 and 0.2 wt%) of carbon-based nanofluids (CBNFs) by a two-step synthesis method as working fluids for heat exchange. CBNFs were actually used in a tube heat exchanger (THE) for heat transfer performance experiments. The heat transfer performance of water and CBNFs was estimated under different heating powers and flow rates of working fluid. The pump power consumption (<i>P<sub>pe</sub></i>) of 0.05 wt% CBNF was found to be similar to that of water, but the <i>P<sub>pe</sub></i> of 0.2 wt% CBNF was higher than that of water. The convective heat transfer coefficient (<i>HTC</i>) of CBNF in the was higher than that of water, and the <i>HTC</i> of 0.05 wt% and 0.2 wt% CBNF was optimal at the heating power of 120 W and 80 W, respectively. The average <i>HTC</i> of 0.05 wt% CBNFs at 120 W heating power was about 3.33% higher than that of water, while that of 0.2 wt% CBNFs at 80 W heating power was about 4.52% higher than that of water. Considering the <i>P<sub>pe</sub></i> and <i>HTC</i> concomitantly, the best overall system performance was exhibited by 0.05 wt% CBNFs.
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