An experiment to examine the cooling process of a hot steel plate by the laminar water flow was carried out and the effect of the water flow rate on the cooling capacity was analytically discussed on the basis of the experimental results. The main points clarified here are as follows:
(1) The vertical distance between a nozzle exit and a cooled plate surface has almost no significant effect on the cooling capacity.
(2) The increase of the water flow rate results in the improvement of the cooling capacity. However, both the cooling capacity and the growth in black zone become saturated with the increase of the flow rate.
(3) The saturation of the cooling capacity is considered to be correlative to that of the growth in the black zone diameter.
