Analysis of mixed convection heat transfer of nanofluids in a minichannel for aiding and opposing flow conditions

Heat transfer characteristics of assisting and opposing laminar flow through a vertical circular tube at low Reynolds numbers

“…As forced convection conditions existed, there was a negligible difference between the Nusselt numbers of opposing and assisting flow, and the Nusselt number results as a function of Reynolds number collapsed onto a single line. This is in contrast to the results in literature on flow through heated vertical tubes [1,12,13,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. A possible reason for this significant difference in trends might be due to the dimensions of the tubes that were investigated.…”

“…In the recent years, there has also been a growing interest in heat exchangers that consist of mini-tubes, rather than macro-tubes. The interest in shift to compact heat exchangers started because these heat exchangers occupy less space, require less material, as well as less heat exchanger fluids [1]. It should, however, be noted these compact heat exchangers are also likely to operate in the laminar flow regime, due to the reduced flow rates through the small hydraulic diameters compared to macro systems.…”

“…Jackson et al [19] gives a comprehensive review of the work done on mixed convective flow using vertical tubes between 1942 and 1989, while Galanis and Behzadmehr [18] reviewed the work done between 1988 and 2008. For vertical tubes heated at a constant heat flux, several analytical [20][21][22][23], experimental [1,12,13,[23][24][25][26][27][28][29][30][31] and numerical [25,[32][33][34][35][36][37][38] studies investigated the heat transfer characteristics.…”

“…In literature [1,12,13,[23][24][25][26][27][28][29][30][31], vertical flow experiments were conducted using test sections with maximum length-to-diameter ratios (L/Di) that varied between 23 and 138, except for two test sections of Kemeny and Somers [12] that had maximum length-to-diameter ratios of 200 and 400. Bashir et al [40] conducted experiments using a test section with a maximum lengthto-diameter ratio of 886.…”

Determination and measurement of some thermophysical properties of nanofluids and comparison with literature studies

“…Fard et al studied about ZnO -water nanofluid in the concentric tube and plate heat exchangers both numerical and experimental [70]. Manay et al [66] have experimentally investigated convective heat transfer of SiO 2water nanofluid. In another study, thermo-physical properties of copper-water nanofluid [57] and ethylene glycol-diethylene glycol mixture based copper nanofluid has worked both experimentally and theoretically by considering the particle size and base fluid [55].…”