In industrial-thermal applications, pulsating flow along with carbon-based nanofluids is a well adopted active method, although not in plate heat exchangers (PHEs). The performance of a PHE with carbon-based nanofluids was experimentally evaluated by superimposing pulsating flow along with steady-state flow. The results demonstrated that the use of GNP-water, hybrid GNP/MWCNT-water, and MWCNT-water nanofluids with volume fractions ranging from 0.01% to 0.1% in a steady-state flow led to improved average heat-transfer rates of 1.34, 1.27, and 1.25, respectively. Furthermore, implementation of pulsating flow enhanced the average heat-transfer rate, in comparison to that of the steady-state flow in the same nanofluids, in the range of 10.9%–28.2%, 9%–25.4%, and 7.1%–14.8%, respectively. Pulsating flow in nanofluids improved heat-transfer rate more than it did in pure water owing to the enhancement of the Brownian motion of the suspended carbon-based nanoparticles. In the considered volume fractions from 0.01% to 0.1%, the pulsating flow condition increased the pressure drop by a factor of 1.48, 1.49, and 1.62 for the MWCNT-water, hybrid GNP/MWCNT-water, and GNP-water nanofluids, respectively, in comparison to pure water. The experimental results indicated that the pulsating flow had a more profound influence on the improvement of heat-transfer rate and pressure drop in the case of GNP-based nanofluid than in the others. This could be attributed to the unique platelet shape of the GNP nanoparticles and consequently the higher Brownian motion. The improvement in the heat-transfer rate, obtained through implementation of the pulsating flow condition, outweighed the cost of increase in pressure drop in all the cases. Among the nanofluids considered, the hybrid GNP/MWCNT-water nanofluid exhibited the best overall performance of 1.2.
Using the Entropy Rate Balance to Determine the Heat Transfer and Work in an Internally Reversible, Polytropic, Steady State Flow Process