抄録
Recently the damages in the tubes of heat exchanger of sea water cooling type have frequently been experienced and the damaged condition could be noticed either from corrosion and erosion on the inner surface of tubes or from pin holes in the tubes.
The damages are considered to have been caused directly from accumulation of marine growth such as sea shells on the inner surface of tubes and from suction of foreign stuff like mud or sand to the heat exchanger.
On the other hand, the unbalancing stream condition in tubes is considered to be the indirect cause of damage.
To investigate the cause, the tank experiment was carried out using a 1/10 scale model to confirm the effect of the unbalanced stream condition of cooling water in tubes and water chambers of main condenser and also in scoop pipe.
In consequence of the above test, we have found out the following:
Extent of unbalance of stream in tubes is rather small despite of some flactuational pressure existing in cooling water inlet chamber of main condenser, however, the phenomenon of cavitation was found to occure around the outlet of inner surface on the tubes near upper part of tube nest located within main stream area when the cooling water velocity in tubes exceeds some limited speed point.
In the light of above experiment, we have confirmed that the excessive cooling water velocity could cause not only inlet-attack but also erosion occurring around the outlet of inner surface on tubes.
