Nanofluids for Heat Exchangers by Hafiz Muhammad Ali & Ali Hassan & Abdul Wahab

Author:Hafiz Muhammad Ali & Ali Hassan & Abdul Wahab
Language: eng
Format: epub
ISBN: 9789811932274
Publisher: Springer Nature Singapore

3.4 Discussion

Comparison of Nusselt number is shown in Fig. 3.13 for different nanofluids and at optimum Reynold number and concentration. Maximum Nusselt number was achieved for SiO2/H2O followed by TiO2/H2O, BeO/H2O and ZnO/H2O. Maximum Nu number of 365 was achieved at Reynold number = 42,000 and 4% volume concentration for SiO2/H2O in double pipe heat exchanger. 346, 345 and 340 Nu number was attained for TiO2/H2O, BeO/H2O and ZnO/H2O at Re = 10,000, respectively. From Fig. 3.13, minimum Nusselt number was gained by using MWCNT/H2O, it was due to the low Reynold number as compared to other nanofluids. Nusselt number gain is enhanced at higher Reynold number because higher Reynold means turbulent flow regime. Hence, in turbulent conditions there is better collision and mixing of nanoparticles which enhanced Brownian motion of particles inside fluid resulted in enhancement of Nu number as well as frictional losses (Fig. 3.14).

Fig. 3.13Schematic of circular tube heat exchanger [67]

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