AbstractHeat transfer from a vertical grid jet within a 2 ft diameter and 4 ft deep fluidized bed of cracking catalyst was studied. The test nozzle diameter was varied from ¼ to 1 in. and the nozzle velocity from 50 to 250 ft /sec which is within the range of industrial practice. The axial temperature data have been related to a Froude, a Reynolds and a Nozzle number:In (δT/δTo) = –58.1 Fr−0.562No1.08Re−0.112A simple jet quenching model yielded heat transfer coefficients between the fluid bed and grid jet which ranged from 300 to 1200 Btu/