Abstract: Numerical simulation was performed to study single-phase convective heat transfer at the impinging zone of non-immersed slot jet by a finite element method (FEM). In combination with the characteristic of rolled quenching machines, some influencing factors on heat transfer such as jet velocity, nozzle-to-impinging plate spacing (height), slot width, jet direction-to-plate angle, and the temperature of water (liquid) from the slot nozzle were analyzed and designed. The results show that, for quenching plates of 100 mm in thickness, the economic process, parameters of slot jet are set as follows:jet velocity 40 to 45 m·s^-1, nozzle-toimpinging plate spacing (height) about 20 mm, slot width about 2 mm, jet direction-to-plate angle about 45°, and the temperature of water (liquid) 10 to 35℃.