Santosh Kumar Nayak

A brief review on viscosity of nanofluids

Since the past decade, rapid development in nanotechnology has produced several aspects for the scientists and technologists to look into. Nanofluid is one of the incredible outcomes of such advancement. Nanofluids (colloidal suspensions of metallic and nonmetallic nanoparticles in conventional base fluids) are best known for their remarkable change to enhanced heat transfer abilities. Earlier research work has already acutely focused on thermal conductivity of nanofluids. However, viscosity is another important property that needs the same attention due to its very crucial impact on heat transfer. Therefore, viscosity of nanofluids should be thoroughly investigated before use for practical heat transfer applications. In this contribution, a brief review on theoretical models is presented precisely. Furthermore, the effects of nanoparticles’ shape and size, temperature, volume concentration, pH, etc. are organized together and reviewed.

Effect of Impingement Density and Nozzle to Target Distance on Spray Cooling of Steel Plate—An Experimental Investigation

ABSTRACT In the steel making industry, high heat fluxes are obtained using effective cooling techniques such as spray impingement cooling. Spray impingement technique involve factors like droplet size, spray height and spray angle, impingement density, and nozzle geometry rendering it very difficult to measure the effects of individual parameters. In the present study, the cooling rate of the plate was experimentally investigated using distilled water as coolant in 3 pressurized nozzles for spray over the surface of the steel plate at elevated temperatures and the behavior of plate temperature with time was tabulated. Cooling curves were generated for different and varying spray parameters like water pressures, nozzle tip to surface distance, and impingement density. It was observed that the cooling rate at the stagnation zone was strongly dependent on the water pressures and nozzle tip to surface distances with maximum cooling rates reaching within 1–2 seconds after the impingement. The average impingement density increased with increase in water pressure and the cooling rate reduces at higher pressures and nozzle tip to surface distances.

Enhancement of heat transfer by water–Al2O3 and water–TiO2 nanofluids jet impingement in cooling hot steel surface

ABSTRACT Two different nanofluids, namely water–Al2O3 and water–TiO2, were impinged in the form of jet on hot steel surface to remove high heat flux, and their performance was compared. The dimension of the test steel sample was 120 mm × 120 mm and 4 mm thickness. Four K-type thermocouples were embedded on the bottom surface of the plate to measure the transient temperature distribution. The time-temperature data were recorded by the help of a data acquisition system (make: CHINO, model: KR2000), and the results were analysed by ZAILA application software. Effect of impinging nanofluids with weight concentrations of 0.01%, 0.03%, 0.05% and 0.07% Al2O3 and TiO2 nanoparticles on heat transfer from the hot surface was tested. The surface heat transfer coefficient (HTC) was computed from the time-temperature history recorded during experimentation. Experimental results revealed that addition of nanoparticles to the base fluid (water) surprisingly enhanced the heat transfer rate and HTC as expected. The heat transfer rate increased up to certain limit of nanoparticle concentrations, and then declined. Application of nanofluids for the steel strip cooling was found very effective in terms of heat transfer phenomena as compared to the conventional fluid cooling methods.

Response surface method-based optimisation of spray parameters during impingement cooling of hot steel in rolling

Response surface methodology was employed for optimising the complex air-water spray mechanisms that occur in hot surface cooling processes where forced convection exists. Results from a physical air-water spray cooling experiment were generated and the experimental parameters were optimised for achieving heat flux from the surface of a hot steel test plate of dimension 120 mm × 120 mm. The thickness of the plate was considered as one of the variable (4 mm, 6 mm and 8 mm) during the experimentation. The other variables in the problem were the nozzle to plate distance, air pressure and water pressure. The experiments were carried out based on the response surface design of experiments. The heat flux was calculated by using Newtons convection model. The optimisation of the controlling parameters was carried out by using the response surface method (RSM). A new mathematical correlation was developed for optimisation of the surface heat flux.

Experimental Result on Heat Transfer during Quenching of Hot Steel Plate by Spray Impingement

ABSTRACT The present article discusses the experimental results on cooling characteristics of a stationary hot steel plate by spray impingement. The experimental setup consisted of an electrically heated flat stationary steel plate of dimension 120 mm × 120 mm × 4 mm, spray setup, water supply, and air supply unit. The effects of various controlling parameters such as air-water pressures, water flow rate, nozzle tip to target distance and impingement density were determined and analyzed. The cooling rates were computed from the time-dependent temperature history and used to analyze the parametric effects. The results obtained in the study confirmed the higher efficiency of the spray cooling system and the cooling strategy was found advantageous over the conventional cooling methods available in the open literature.