Cooling Heat Transfer from a Rotating Roll by Impinging Water Spray Jets

The cooling heat transfer by impinging water spray jets on a rotating roll with a relatively large diameter has been investigated under various experimental conditions with 3 different sizes of flat type nozzle. The local heat transfer coefficients were calculated by finite difference method using measured surface temperatures of the circular cylinder as boundary conditions. Results show that a peak value of the heat transfer coefficient is located at the center of sprayed area and there may be a secondary peak at the downstream. The average heat transfer coefficients on the sprayed area were found to be 10 to 22 ㎾/, and were not related to spraying pressure, but approximately linearly to flow rate of sprayed water. Also it is found that increasing the distance from roll to nozzle could improve the cooling efficiency by increasing the sprayed area.