Second law analysis of water flow through smooth microtubes under adiabatic conditions

Fluid Mechanics, Heat Transfer and Thermodynamic Issues of Micropipe Flows

“…Table 2 q and with lower d. The present evaluations can be detailed by the two fundamental reporting: Promoted total entropy generation (i) with low micropipe diameters and high fluid velocities is due to frictional entropy generation (Table 1), (ii) with the application of higher heat flux, bigger micropipe diameters and low Reynolds numbers count on thermal generation rates (Table 2). Enhanced entropy generation rates with higher Reynolds numbers and lower micropipe diameters are as well reported by Avci & Aydin (2007), Hooman (2008) and Parlak et al (2011). In addition to the above determinations, through the ratio of S is identified with the following comparison rates of 3.692→2.068 (d=1.00→0.50 mm) (Re=100), 1.782→1.064 (Re=500), 1.241→1.015 (Re=1000) and 1.061→1.003 (Re=2000).…”

“…Guo & Li (2003) studied the mechanism of surface roughness provoked surface friction and concluded that the early transition from laminar to turbulent flow arose due to the frictional activity. Smooth micro-tubes under adiabatic conditions were experimentally investigated by Parlak et al (2011); they determined that, as long as the viscous heating effects are taken into account for micropipe diameters of d<100 µm, the measured data and the calculated data from Hagen-Poiseuille equation of laminar flow are fairly comparable. The works of Celata et al (2006a,b) described the roles of surface roughness on viscous dissipation, the resulting earlier transitional activity, augmented friction factor values and elevated head loss data.…”

“…On the other hand, with the increase of Reynolds number the variation rates in C f , at different micropipe diameter cases, become stronger with the particular values of 3.4→4.2% (d=1.00→0.50 mm), 6.6→8.1%, 9.6→11.9% and 12.4→15.2% for Re=500, 1000, 1500 and 2000. Renaud et al (2008), Almeida et al (2010) and Parlak et al (2011) also shown the grow of frictional activity in micropipes with lower diameters. As shown in Fig.…”

“…Ko (2006a) carried out a numerical work on the thermal design of a double-sine duct plate heat exchanger, from the point of entropy generation and exergy utilization. Second law characteristics in smooth micropipe were experimentally investigated by Parlak et al (2011); they recorded augmentations in entropy generation with higher Reynolds number and with lower micropipe diameter. Sahin (1998), for a fully developed laminar viscous flow in a duct subjected to constant wall temperature, inspected the entropy generation analytically.…”

Compressibility and rarefaction effects on entropy and entropy generation in micro/nano Couette flow using DSMC

“…They showed that entropy generation regions are related to the thermal non-equilibrium regions in the flow field. Parlak et al [27] studied steady-laminar flow of water in adiabatic microtubes experimentally and analytically. Through employing the second law analysis, they showed that the flow characteristics in the smooth microtubes distinguish substantially from the conventional theory for flow in larger tubes with respect to viscous heating/dissipation, temperature rise of flow, total entropy generation rate and lost work.…”