1968 Volume 54 Issue 14 Pages 1457-1471
The cooling process of plain carbon steel plate was studied. A plate of 28 × 220 × 220 mms size was heated up to 930°C and then cooled by water spray from both sides; the temperature of cooling water was 38°C. The results obtained are as follows;
1. The heat transfer coefficient α' decreases gradually as the temperature of cooled surface θsis raised when water flow rate of spray W is large, while in the case whereWis small, the coefficient decreases abruptly with the elevation of θsover 300°C.
2. The relation between α′ and W is described as “α′∝Wn” in the case of W>5 × 10-4 1/cm.2rnin, and values of n are divided into two groups according to the boiling condition of cooling water, i. e.groups of value having 03-0.5 and0.5-0.8
3. The relation between the mean heat transfer coefficient and W is described as “α∝W0.65-0.75” in the case of W>5 × 10-41/cm2.min.
4. The relation between a and cooling water temperature θW(°C) is described as “α∝ [1-(5-8)×10-3θw]” in the case of W=0.060-%-0.062 1/crn2.min.
5. When W is large, the cooling rate V is hardly influenced by Os, but increases abruptly for 0, lower than about 500°C when W is small. Furthermore, V' decreases regardless of W, in such a temperature region that the transformation heat is evolved.
6. The relation between the mean cooling rate V- andWis described as “vcx 1470.-0.7” in the case of W=5 ×10-4-8 × 10-2 l/cm2-min.
7. The relation between V and θw(°C) is described as “V∝ [1 (4.5-5.5)× 10-3θw]” in the case of W=0.060-0.062l/cm2.min.
8. It is deduced that “spray cooling is a sort of turbulent flow cooling” from the quantitative relation between the water flow rate of spray W and heat transfer coefficient a, i. e.“α∝Wn” where values ofnis about0.5-0.8.