izvorni znanstveni rad
Introducing nanofluids as liquid quenchants in order to improve heat transfer characteristics is a novel approach in heat treatment. These new liquid quenchants are called nanoquenchants, which are colloid suspensions of nanoparticles in base fluid (BF). For the purpose of this research standard liquid quenchants, such as water and polymer solution, were used as base fluids. Nanoparticles are added to the base fluid in order to increase its’ thermal properties without great effect on viscosity of the fluid. Added nanoparticles cause an enhancement of heat transfer characteristics of liquid quenchants. In this research TiO2 nanoparticles, average size 50 nm, were added to the base fluid. Cooling curves for every tested quenchant were recorded using IVF SmartQuench system and quenching process parameters were determined and compared. Tested quenchants were deionized water and polyalkylene glycol (PAG) water solutions of 5, 10 and 20 %vol. polymer concentrations. Quenching experiments were first conducted in pure BF without the addition of nanoparticles and without agitation according to ISO 9950 standard. The experiments were than repeated with the addition of 0.2 g/l TiO2 nanoparticles. Second series of experiments were conducted in quenching bath with agitation according to ASTM D 6482 standard. All of the recorded cooling curves were compared and the effect of nanoparticle addition and agitation were investigated. The addition of nanoparticles and quenching with agitation caused the increase in maximum cooling rate and shorter full-film stage.
nanofluids ; quenching ; agitation ; cooling characteristics
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