Impingement heat transfer and recovery effect with submerged jets of large Prandtl number liquid—II. Initially laminar confined slot jets

Abstract

Local measurements were made to determine recovery factors and heat transfer coefficients resulting from the impingement of transformer oil jets issuing from tiny slot nozzles of 0.091, 0.146, and 0.234 mm in width. This study focused on initially laminar jets in the range of jet Reynolds number between 55 and 415, and fluid Prandtl number between 200 and 270. Lateral distribution of local recovery factor was measured at various Reynolds numbers and nozzle-to-plate distances. Stagnation point heat transfer coefficient was collected and correlated as a function of jet Reynolds number, nozzle-to-plate spacing and nozzle width. Twenty seven lateral profiles of local heat transfer were obtained and correlated. Nonmonotonic variation and unusual behavior of local heat transfer were observed and attributed to possible transition from laminar to turbulent regime. Based on the measured local data, integral average heat transfer rate was determined and correlated.