Second-law analysis of laminar nonnewtonian gravity-driven liquid film along an inclined heated plate with viscous dissipation effect

Abstract

-A second-law analysis of a gravity-driven film of non-Newtonian fluid along an inclined heated plate is investigated. The flow is assumed to be steady, laminar and fully-developed. The upper surface of the liquid film is considered to be free and adiabatic. The effect of heat generation by viscous dissipation is included. Velocity, temperature and entropy generation profiles are presented. The effects of the flow behaviour index, the Brinkman number and the group parameter on velocity, temperature and entropy generation number are discussed. The results show that velocity profile depends largely on the flow behaviour index. They are flat near the free surface for pseudoplastic fluids and linear for dilatant fluids. Temperature profiles are higher for higher flow behaviour index and Brinkman number. The entropy generation number increases with Brinkman number and the group parameter because of the heat generated by the viscous dissipation effect. For pseudoplastic fluids, the irreversibility is dominated by heat transfer, whereas, for dilatant fluids, irreversibility due to fluid friction is more dominant.

Entropy analysis for the Couette flow of non-Newtonian fluids between asymmetrically heated parallel plates: effect of applied pressure gradient

“…It is noteworthy that, for Newtonian fluid, the velocity profile shows the usual trend of parabolic shape. However, the velocity profile obtained in this study even for all types of power-law fluids considered shows similarity with the published results [22,24]. On the other hand, in figure 3(b), the variation of velocity distribution in the flow field specific to the case of the strong applied pressure gradient γ = ( 0.2) has been displayed.…”

“…2, the entropy generation number for the pseudoplastic < n ( 1) fluid is higher for a relatively higher value of group parameter, which one can find from figure 6(b) presented above. However, the variation of N S observed from the figures under consideration, 6(b) and (c), shows similarity with the results available in the existing literature [22,24].…”

“…A closer look at figure 4(a) reveals an important observation that the fluid temperature increases with the decreasing value of the fluid behaviour index n, i.e., with the reduced strength of the non-Newtonian behaviour of the fluids. The observations seen from the figure contradict the behaviour of temperature distribution reported in [22,24], primarily because the thermal boundary condition considered in this analysis together with the movement of the top plate. The movement of the top plate introduces additional heat in the flow field following the fluid friction effect and, hence, strengthens the fluid temperature.…”

“…However, in the process considered in this analysis, irreversibility arises from two different effects: one is due to the heat transfer between the fluid and solid walls and the second one is essentially due to viscous heating. The general expression for the volumetric entropy generation rate for the non-Newtonian fluid in a dimensional form is given by [8,20,22,24,27]:…”

“…A closer review of the available literature regarding irreversibility analyses of thermodynamic systems and processes clearly reveals that researchers have considered the effect of fluid rheology, while investigating the entropy generation rate of the systems involved in thermo-fluidic transport [20,21]. However, in many cases, researchers have considered the power-law model in the analysis to represent non-Newtonian fluid rheology and have investigated the entropy generation rate attached to the convective heat transport either between two parallel plate channels or on an inclined plane surface [21][22][23][24].…”