Numerical Study of Heat Transfer Characteristics of Laminar Nanofluids Flow in Oblique Finned Microchannel Heat Sink: Effects of Different Base Fluids and Volume Fraction of Nanoparticles

This paper demonstrates a numerical study of heat transfer characteristics of laminar flow in oblique finned microchannel heat sink using nanofluid with nanoparticles added to various base fluids including water, ethylene glycol and turbine oil as coolant fluid. The width of the primary channel was 0.5 mm and the secondary channel was less than 0.15 mm in the oblique finned microchannel heat sink with an aspect ratio of 3. ANSYS Fluent was employed to model the flow in the geometry of microchannel. Single phase model and constant heat flux boundary condition were used in this numerical study. The modeling was validated by comparing the published data for conventional and enhanced microchannel heat sink. The base fluid acted as a comparison baseline to the nanofluid with volume fraction of 1.0% and 4.0%. Besides, the study was carried out in laminar flow regime, whereby the Reynold number ranged between 320 to 700. It was found that turbine oil based nanofluid had the highest Nusselt number among all fluids, followed by ethylene glycol and water to be the least. However, the heat transfer coefficient among all fluids were contrary to the Nusselt number where water achieved the highest heat transfer coefficient. The addition of nanoparticles increased the heat transfer coefficient of all fluids but it did not enhance their Nusselt number except water.

Experimental evaluation of toxicity and neuroparalitical actions of fire-resistant turbine oil «Turbomas»

The article presents the results of a study of the toxicity of fire-resistant turbine oil «Turbomas «, a derivative of diphenyl-(n-tert-butylphenyl phosphate). According to toxicity parameters, «Turbomas» oil is characterized as a low-toxic compound, does not have neuroparalytic action, exhibits mild cumulative properties, does not irritate the skin and mucous membranes, penetrates intact skin,

Estimation of the Oxidative Deterioration of Turbine Oil Using Membrane Patch Color

Lubricating oils degrade into two main products: oxidation products and solid particles. Oxidation products, called varnish, of turbine oils for power generation have become a particularly serious problem in recent years. The first step in determining the potential to produce varnish is to determine the remaining life of the antioxidant in the oil, but even though turbine oil may have antioxidants of sufficient longevity, varnish problems still occur frequently. Accordingly, to prevent varnish, it is necessary to diagnose oil oxidation products. Thus, the authors have developed a diagnostic method using membrane patch color, but the relationship between membrane patch color and the remaining life of turbine oils has yet to be clarified. This paper investigates a new method for estimating the oxidative degradation of turbine oils that uses membrane patch color and the dry turbine oxidation stability test (dry TOST) based on oxidation products and the remaining life of the turbine oils. Sample oils were prepared and degraded by oxidation in the laboratory using a dry TOST apparatus, and the membrane patch color was measured using a colorimetric patch analyzer (CPA). The relationship between membrane patch color and the rotating pressure vessel oxidation test (RPVOT) residual rate was then investigated. The results show that the new estimation method using the CPA and dry TOST is able to monitor the decrease of the RPVOT residual rate from the early stages of oxidative deterioration.