Temperature dependent viscosity effects on laminar forced convection in the entrance region of straight ducts

Viscous dissipation and temperature dependent viscosity effects in simultaneously developing flows in flat microchannels with convective boundary conditions

“…In all the computations, the axial step has gradually been increased from the starting value ∆x/D h = 0.0001 to the maximum value ∆x/D h = 0.05. The procedure outlined in the previous section and employed for the numerical simulations had already been validated, on the assumptions of constant property fluid and negligible viscous dissipation, by comparing heat transfer and pressure drop results with existing literature data for laminar simultaneously developing flows in straight channels, both three-dimensional and axial-symmetric [6,9,10]. In order to assess the accuracy of the present computations, additional validation tests have been carried out.…”

“…Moreover, in many situations of practical interest, fluid velocity and temperature fields develop simultaneously, resulting in overlapping hydrodynamic and thermal entrance regions. This occurs when fluid heating or cooling begins at the microchannel inlet, where also the velocity boundary layer with temperature dependent viscosity in straight macro-and microchannels [9,10] and, on the additional assumptions of non-negligible viscous dissipation effects, in the study of thermally and simultaneously developing liquid flows in microchannels when prescribed constant temperature boundary conditions are applied to the rigid walls [1,2]. Here the same procedure is used to study a similar problem with reference to flows in flat microchannels with convective thermal boundary conditions.…”

Numerical analysis of the axial heat conduction with variable fluid properties in a forced laminar flow tube

“…Lelea [22] investigated the conjugate heat transfer of the variable-property water flow inside the microtube and analyzed the influence of the heating position, tube material, wall thickness and Re upon the thermal parameters. Nonino et al [23] investigated the laminar forced convection at the entrance region of the straight ducts with variable viscosity according to an exponential relation by a finite element procedure, considering different cross-sectional geometries. Afterwards, they adopted the same procedure to study the effects of the viscous dissipation and temperature dependent viscosity in thermally and simultaneously developing laminar flows [24].…”

Effects of viscous dissipation and temperature dependent viscosity in thermally and simultaneously developing laminar flows in microchannels

“…Due to the high value of the ratio between the total length and the hydraulic diameter in microchannels, such an approach is very advantageous with respect to the one based on the steady-state solution of the elliptic form of the governing equations in a three-dimensional domain corresponding to the whole microchannel. The procedure has already been used, disregarding viscous dissipation effects, in the simulation of simultaneously developing flows of liquids with temperature dependent viscosity in straight macro-and microchannels (Nonino et al, 2005a;Nonino et al, 2005b). Here, the procedure is also validated for non-negligible viscous dissipation effects with reference to thermal entrance flow of a constant property fluid in circular ducts (Basu and Roy, 1985).…”