Mixed Convection Heat Transfer of Sio2-Water and Alumina-Pao Nano-Lubricants Used in a Mechanical Ball Bearing

Abstract

In this study, the mixed convection heat transfer in a mechanical ball bearing filled with nano-lubricants were investigated theoretically. In our case, the bearing including eight balls revolving in counter clockwise while the inner shaft rotates in clockwise direction and the inner and outer walls of bearing were kept at constant hot and cold temperatures, respectively. Two kinds of nano-lubricants SiO2-water and Alumina-Polyalphaolefin (PAO) with different shapes of nanoparticles were considered. The governing equations including velocity, pressure, and temperature formulation were solved based on the Galerkin finite element method. The governing parameters such as nanoparticle volume fraction, Reynolds and Rayleigh numbers, etc., were discussed. It turns out that the average Nusselt number increases by increasing the nanoparticle volume fraction (averagely 15% for each 0.02 increase) and the oil-based nano-lubricant has greater Nusselt number than the water based one. More importantly, the Nono-rod Alumina was found to show much greater heat transfer performance (averagely 5%) than the spherical alumina nanoparticles and nano-rod Alumina-PAO has the best performance and maximum Nusselt numbers for the heat transfer.

Thermal Analysis of a Reactive Variable Viscosity TiO2-PAO Nanolubricant in a Microchannel Poiseuille Flow

“…Under these conditions, the continuity, momentum, and energy equations governing the problem in dimensionless form may be written as [ 5 , 14 , 19 , 20 , 21 ] where …”

“…Following [ 5 , 10 , 18 , 20 ], the thermophysical expressions for variable viscosity reactive nanolubricant with respect to the nanoparticles are given as follows where is the density of the PAO lubricant, is the density of the solid nanoparticle, k f is the PAO lubricant thermal conductivity, k s is the nanoparticle thermal conductivity, ϕ is the TiO 2 nanoparticle volume fraction and μ f is the PAO lubricant dynamic viscosity. The physical properties of PAO lubricant together with TiO 2 nanoparticles are listed in Table 1 below.…”

“…The microchannel configuration is aligned with the x-axis where the y-axis is normal to it, as shown in Figure 1 below. Under these conditions, the continuity, momentum, and energy equations governing the problem in dimensionless form may be written as [5,14,[19][20][21] Under these conditions, the continuity, momentum, and energy equations governing the problem in dimensionless form may be written as [5,14,[19][20][21] ∂u ∂x…”

“…In addition, fuel and lubricant consumption are cut, and harmful emissions are reduced. Recently, several researchers and scientists [ 4 , 5 , 6 , 7 ] have conducted both experimental and theoretical studies on nanolubricants due to their tremendous applications. Borda et al [ 8 ] experimentally examined the tribological behaviour of nanolubricants containing copper as nanoparticles.…”

A Comprehensive Review of Water-Based Nanolubricants

“…Apart from the van der Waals, depletion, and steric stability forces, the Brownian force [213,214], buoyancy force [215], hydration force [216], and interphase resistance [217] may also contribute to the dispersion stability of nanofluids under specific conditions.…”