Experimental Study Of The Impact Of Spraying And Immersion Cooling On High Temperature Plate

Controlled cooling is aimed at improving the structure and the properties of steelby controlling the cooling rate after rolling steel plate. It is also a kind of technologyused to enhance the precipitation effects by refining the ferrite grain, reducing thespacing between pearlite interlamellar and preventing the precipitation of carbides athigh temperatures and regarded as a method of heat treatment such as online cooling.Spray cooling is one of the most important controlled cooling technology. During theperiod of cooling, the heat transfer coefficient of spraying surface is an importantparameter to quantify the cooling capacity of the cooling medium and it is also animportant parameter in cooling control design. In this paper, we take experiments oncylindrical nozzle, scattering nozzle and crevice nozzle and explore the influence ofplate thickness on the spray cooling. Apart form the spraying experiment, the effect ofthe immersion cooling parameters has been studied in this paper as well.We found that with the increasing pressure of impact zone, the central cooling ratespeeds up and the capacity of heat transfer of spray surface increases. As for thecylindrical hole nozzle, the influence on cooling the surface of steel becomes weak. Asfor the scattering angle nozzle and slit injector, this phenomenon is not obvious.Spraying height does not have a big influence on heat transfer, in most cases, coolingbecomes slightly faster when the spray height is100mm. Heat transfer is very complexin advection zone while quite uniform in scattering angle nozzle, central cooling ratebecomes faster while the pressure speeds up. Capacity of heat transfer enhanced whilethe spray height increases.The gap type peaks at the circumstance of0.5MPa whilehole cylindrical peaks at0.8MPa.When we use the inclined spray, the cooling rate of impact zone decreases and theheat transfer coefficient reduced while the cooling rate of stratospheric acceleratesnoticeably along with the heat transfer coefficient (relative to the vertical spray). In theprocess of cooling, the temperature difference of impact zone and advection zonebecome smaller. The use of inclined spray improves all the uniformity significantly inthe whole steel plate. When we use vertical spray, the minimum temperature differencebetween impact zone and advection zone and the best temperature uniformity have beengot using the Scattering angle nozzle.According to the heat flux and heat transfer coefficient along with the Ja curve, when Ja is bigger than0.3, the heat flow of the upper and lower surface changedramatically with the change of Ja. As the Ja declines, the heat flux gradually rise ordecline and finally dropped sharply. Heat transfer coefficient h rises up with the declineof Ja and than arrive at the maximum. The heat transfer coefficient rises and thendeclines during the period of cooling and the maximum appears when Ja is between0.03and0.08.The research found that the thickness of steel plate doesn’t have any significantimpact on the capacity of the surface of steel plate while the cooling rate of the centralsteel plate decreases dramatically with the increases of the thickness of steel plate.In this paper, we establish three nozzle spray cooling heat transfer coefficientprediction model based on the boiling theory and cooling experiment which have beprovided by previous research.Model predictions and experimental results agree well with the hole cylindricalnozzle and the scattering angle nozzle error less than+-30%while the gap nozzle errorwithin+-40%. Surface temperature changes in the spray cooling process for the projectin the most widely used range from the early cold to a Jacques created than the numberof average hear transfer coefficient prediction model, model predictions andexperimental results are in good agreement.What’s more, under the immersion cooling condition, the liquid spatters canpre-cool the plate at high temperature; the heat transfer in the vertical direction has beenenhanced with the increasing liquid level and the center temperature cooling speed isvery high. The experiments reveal that the nonlinear relationship between the centertemperature dropping speed and the liquid level increasing speed, and it shows anU-shape trend which suggests that a minimum center temperature dropping speed existsduring rewetting with a certain liquid level increasing speed. With higher initialtemperature, the temperature dropping speed is affected by the initial temperaturemildly.