HEAT-TRANSFER BETWEEN A HEATED PLATE AND AN IMPINGING TRANSIENT DIESEL SPRAY

An experimental investigation was performed to determine the heat-tran sfer distribution in the vicinity of a transient diesel spray impingin g on a heated flat plate. The spray prior to impingement was character ised in terms of simultaneous droplet sizes and velocities by phase-Do ppler anemometry while during its impingement on the plate, which was heated at temperatures between 150-205-degrees-C, the instantaneous su rface temperature and associated rates of wall heat transfer were moni tored by fast response thermocouples. The parameters examined in this work included the distance between the nozzle and the wall surface, th e radial distance from the impingement point, the injection frequency, the injected volume and the pre-impingement wall temperature. The res ults showed that the wall heat transfer rates are dependent on the spr ay characteristics prior to impingement; the higher the ''velocity of arrival'' of the droplet is, the higher the heat transfer. A correlati on was thus developed for the instantaneous and spatially-resolved spr ay/wall heat transfer based on experimentally-determined Nusselt, Reyn olds, Prandtl and Weber numbers over a wide range of test conditions.