Investigation of the impact of the spray cooling process using various spray nozzles on the unevenness of energy transfer from the metal surface

Cooling systems often rely on numerical calculations with precise heat transfer boundary conditions (HTBC), usually expressed as average values. The value of the average HTBC depends on the area in which they are determined. The paper presents a new approach showing the influence of the choice of the method of supplying liquid onto the surface on the non-uniformity of energy transfer from the cooled surface, which is important in the selection of the determination domain on the HTBC. The tests were carried out for two full-cone nozzles with different spray angles and two materials with different thermal properties. The local and average heat fluxes were determined for various distances of the nozzles from the surface and various liquid supply pressures. Cooling capacity, unevenness of energy transfer from the surface and quenching characteristics were evaluated and assessed using cooling curves. The study concludes that adopting HTBC based on average heat flux variation does not cause a significant error in the assessment of energy transfer during cooling with a nozzle with spray angle of 60° for EN 1.4845 steel. However, for Inconel and a nozzle with spray angle of 45°, the noticeable non-uniformity requires the application of a local HTBC.