1978 Volume 64 Issue 1 Pages 70-77
When an immersion method is used for the cooling of heated steel products, it is important that the characteristics of this method are made clear. In order to measure the values of heat transfer coefficient between a specimen and coolant, and to clarify the influence of coolant stirring on heat transfer, 28×550×1000mm3 steel plates of about 930°C have been immersed into still water or stirred water.
The main results obtained are summarized as follows:
(1) When a specimen is immersed vertically into water, the maximum of heat transfer coefficient between the specimen and water (α) is, in kcal/mm2·h·deg, (5-7) ×103 for still water, (7-9) ×103 for stirred water by air flow, and (10-12) ×103 for stirred water by water flow.
(2) In a vertical immersion into still water, α is considered to be a function of the surface temperature of a specimen, θs, and the height from the lower edge, H, as indicated below.
α=10 (a+b·θs) · [1.0-k (H-10)]
Where a, b, and k are constants which depend on θs.
(3) When a specimen is immersed vertically into still water, αdecreases with increasing the size of the specimen.
(4) The stirring of coolant by fluid flow is effective for the accelaration of the heat transfer and the water flow method is superior to the air flow one.