噴霧および衝風の冷却能に関する研究

抄録

With the purpose of utilizing sprayed jet cooling and air blast cooling to the heat treatment of the steel the heat transfer coefficient α was measured and some considerations were given.
The main results obtained are as follows:
a) Air blast cooling
Following empirical formula are obtained with the range of experiments, 3×10³≤R_e≤2×10⁴, 0.02≤D≤0.04 [m] and 100≤T≤600 [°C].
Nu_a=3.25Re^0.45 (D/D₀) ^-0.1 (v/v₀) ^0.2
Nu_a: Nusselt number Re: Reynolds number
D: diameter of specimen disc v: velocity of air D₀=0.03 [m] v=8.94 [m/sec]
b) Sprayed jet cooling
1. There are three stages in the cooling process; they are termed as the high temperature, transition, and low temperature stages. The cooling mechanisms in these stages are considered.
2. In the high temperature stage, α is the sum of those of air blast cooling and the cooling due to evaporation of water droplets.
3. The fraction of water quantity, K, which is effective for cooling by evaporation in the high temperature stage does not change with the water quantity and the temperature, when the sprayed jet velocity is constant.
4. The value of K increases with v. In the range of this experiments following equation is obtained.
K=3.2×10^-v v: [m/sec]