Ishita Sarkar

Heat Transfer from a Hot Moving Steel Plate by Air-Atomized Spray Impingement

Air-atomized spray cooling of a hot moving AISI 304 steel plate of 6 mm thickness has been investigated experimentally by varying water flow rate and plate velocity at a fixed nozzle-to-plate distance. It is found that the heat transfer coefficient is a non-linear function of surface temperature. The result shows that the cooling rate increases with an increase in the water flow rate. The highest cooling rate has been found for the static plate, whereas for a moving plate, an increasing cooling rate trend has been observed with increasing plate velocity.

Heat transfer from a hot moving steel plate by using Cu-Al layered double hydroxide nanofluid based air atomized spray

ABSTRACT The current research is focused on the cooling of a hot moving steel plate by using air atomized spray cooling technique. A new type of coolant, Cu-Al LDH nanofluid, has been prepared and used for heat flux removal. Preparation method of nanofluid and its characteristics has been reported. The cooling effectiveness is reported in terms of cooling rate by varying the concentration of nanofluid in five levels. The results indicate that the cooling rate increases at very low concentration of LDH with respect to base fluid. However, beyond a certain concentration a decreasing trend of cooling rate has been observed. Abbreviations: CHF: Critical heat flux; HTC: Heat transfer coefficients; LDH:Layered double hydroxide; TEM: Transmission electron microscopy.

Jet Impingement Cooling of a Hot Moving Steel Plate: An Experimental Study

In the current study, a hot moving steel plate of 6 mm thickness with an initial temperature of 900°C has been considered for jet impingement cooling. The experiment has been designed with the help of Design of Expert software to optimize the process parameters based on the highest cooling rate. The various subsurface transient temperature histories have been measured during the cooling process. The surface heat flux and surface temperature were calculated with the help of a commercial inverse heat transfer solver called INTEMP. The experimental result has been presented in terms of cooling rate and critical heat flux.

Ultrafast cooling of medium carbon steel strip by air atomised water sprays with dissolved additives

Abstract Ultrafast cooling is a newly developing heat treatment technique that can be used for the production of advanced high strength steels. Conventional laminar jet cooling is generally fitted in the runout table; however, it cannot provide the higher cooling rates necessary, and air atomised spray cooling can be the best alternative for ultrafast cooling rates. As water is the commonly used coolant, it is beneficial to know the effect of surface active or volatile additives on the cooling characteristics for high heat flux applications. Thus, this study examines the two aspects of the use of enhancement of air atomised water spray cooling process with a mixture of ethanol and surfactant additives. First, additive based cooling of stainless steel strip was evaluated to optimise the cooling rate, then these optimum parameters were used to study the improvement in mechanical properties and microstructure of medium carbon steel compared to pure water ultrafast cooling. The cooling experiments were carried out at a temperature above the Leidenfrost point of the hot strip. A commercial inverse solver called INTEMP was used for the calculation of surface temperature and heat fluxes. It was observed that the addition of surfactants and alcohol enhanced the cooling rate and critical heat flux of the test strip and has higher impact on martensite phase evolution.

Application of TiO2 nanofluid-based coolant for jet impingement quenching of a hot steel plate

ABSTRACT Cooling rate in Run Out Table (ROT) in steel industries tailors microstructure which lead to improved mechanical properties. The current work aims to increase cooling performance of steel using TiO2 nanofluid as coolant in jet impingement. Different concentrations of TiO2 nanofluid have been used to study effect on jet cooling of a steel plate from 900°C. Thermal conductivity of nanofluid is found to significantly enhance at optimum concentration and this plays major role in increasing cooling rate of the steel plate. 19% enhancement in cooling rate is observed by using 40 ppm of TiO2 nanofluid compared to water.