A. Szajding

Inverse method implementation to heat transfer coefficient determination over the plate cooled by water spray

The three-dimensional (3D) inverse solution to water spray cooling from 925 °C to room temperature of the AISI 309 steel plate has been presented. The finite element method with linear and nonlinear shape function has been employed in forward simulations of the plate temperature and in the inverse solutions. The forward finite element solvers have been first compared with the analytical solution to the plate cooling. The reduced finite element models have been compared with the reference model for plate cooling under variable in time and space heat transfer coefficient (HTC) and for the temperature-dependent thermophysical properties of steel. It has been shown that the reduced finite element model with only 216 degrees of freedom which utilizes nonlinear shape functions has given the inverse solution to the heat transfer at the cooled surface with the accuracy of 1.6%. The influence of the thermocouple location uncertainty and the temperature dependence of thermophysical properties have been tested in inverse solutions. The implementation of the reduced finite element heat conduction models and the function specification method in space and time have allowed to achieve the 3D inverse solution to the overall heat transfer at the cooled surface with the accuracy of 2%. The developed 3D inverse solution has been employed to the determination of the HTC distribution over the AISI 309 steel plate cooled by the water spray nozzle. The thermal characteristic of the full cone swirl spray nozzle has been developed.

Heat transfer coefficient distribution over the inconel plate cooled from high temperature by the array of water jets

The industrial rolling mills are equipped with systems for controlled water cooling of hot steel products. A cooling rate affects the final mechanical properties of steel which are strongly dependent on microstructure evolution processes. In case of water jets cooling the heat transfer boundary condition can be defined by the heat transfer coefficient. In the present study one and three dimensional heat conduction models have been employed in the inverse solution to heat transfer coefficient. The inconel plate has been heated to about 900oC and then cooled by one, two and six water jets. The plate temperature has been measured by 30 thermocouples. The heat transfer coefficient distributions at plate surface have been determined in time of cooling.