Enhanced Heat Transfer Mechanism of Nanofluids Minimum Lubrication Grinding

2.1 Introduction

Nano fluids are the unique family of fluids which are synthetized by dispersing nano size matter as nanowires, nano-particles and nano-tubes in base fluids. The dispersion of solid particles in base fluids have great potential in heat-management fluids (Keblinski et al., 2002). The advancement in nanotechnology along with applications of nanofluids in heat transfer brought breakthrough in this field (Safaei et al., 2016).

The history of nanofluids started with enhancing single-phase fluids thermal conductivity by adding particles which firstly represented by Maxwell (1873) but the technique failed due to sedimentation and clogging problems. Masuda et al. (1993) proceeded the Maxwell work and achieved increment of thermal conductivity by adding micro-sized nanoparticles but the performance was low. Choi and Eastman (1995) introduced nanofluids by dispersing nanosized particles into base fluid. The resulted substance exhibited better performance having good thermophysical properties with minor stability problems. The various studied on progress on nano fluids (Trisaksri and Wongwises, 2007; Özerinç et al., 2010; Wang and Mujumdar, 2007; Wang and Mujumdar, 2008; Li et al., 2009; Kakaç and Pramuanjaroenkij, 2009) concerned with studies of thermophysical properties and convective heat transfer coefficient of nano fluids. Nanofluids are used in increasing rate of heat transfer by enhancement of “h” due to increment in thermal conductivity. When nanoparticles are present in base fluid then each particle gets electrically charged by absorbing and desorbing an electron (Popa et al., 2010).

The Vander Waals forces dominant to attractive forces in case of stable nanofluids which is vital factor in increasing thermal conductivity (Jang and Choi, 2004; Xuan et al, 2003). Thus, the nanofluids (Mukherjee and Paria, 2013) have potential features which distinguished from other fluids such as:

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  Increase of thermal conductivity

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  High heat transfer capability

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  Stability good as compared to other colloidal

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  Reduce power of pumping

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  Reduction coefficient of friction

2.2 Preparation Of Nanofluids

The preparation of nanofluids is to be done by proper mixing of nano particles by utilization of various methods involved in it. The nanofluids preparation can be categorized to two basic categories based on number of steps which are single and two steps preparation method. The Figure 1 indicates various techniques for preparation of nanofluids.

Figure 1.

Various methods in nanofluids preparation

2.2.1 One-Step Method

Single-step involves the nanofluid preparation by combining the production and nanoparticles dispersion with base fluid, but these two steps occurred at a once time as illustrated in Figure 2. The various methods included in single-step method are laser ablation, vapor deposition and submerged arc (Ali et al., 2018).

Figure 2.

Preparation of nanofluid using Single Step method (Ali et al., 2018)

The nanoparticles are directly produced by condensation of nanoparticles from vapor phase into low vapor pressure fluid called VEROS (vacuum evaporation on running oil substrate) or Physical deposition technique (Akoh et al., 1978). Choi et al., (2001) investigated direct evaporation condensation method which result in best control size of nanoparticles and stable nanofluid without adding additive. Eastman et al. (1996) utilized VEROS method which involved condensation of vapors of metal to nanoparticles and dispersed into base fluid directly.