Determination of effective heat transfer area on vertical surfaces subject to spray and impinging jet

•Method for detecting the heat transfer area for spray cooling below boiling point.•Method that provides information about size and shape of the heat transfer area.•Investigation of a full cone, hollow cone and jet nozzle spray.•Influence of nozzle pressure, nozzle to target distance and nozzle inclination. In this paper a method is introduced to determine the area primarily contributing to heat transfer of spray and jet impingement cooling below boiling point. The setup is based on temperature measurement via an infrared camera. This camera is pointed at the back of a metal plate, whereas the nozzle is spraying from the front. This technique is especially suitable for heat transfer areas with different shapes, as it occurs with different nozzle types. The analysis of the heat transfer area uses a temperature criterion based on the second derivative of the temperature distribution. Using this method the heat transfer areas generated by a full cone nozzle, a hollow cone nozzle and a jet nozzle have been studied. The study focused on the influence of nozzle pressure, nozzle to target distance and nozzle inclination on the heat transfer area. The results show, that the heat transfer area generated by different nozzle types have similar behavior regarding nozzle pressure, but different behavior in terms of distance variation and nozzle inclination.