BOILING PHENOMENA OF COOLING WATER IN THE PERMANENT MOLD

The boiling phenomena of water in a cooling channel within a permanent mold were studied. The test consisted of heating the mold to high temperatures 1300 degrees C (2372 degrees F) for 0.5 ms (milliseconds) followed by low temperatures 200 degrees C (392 degrees F) for 49.5 ms. This heating procedure was to simulate the heating condition on the copper wheel mold applied in planar flow casting process. When the velocity of water into the channel was under a critical velocity (1.9 m/s), the boiling condition of the coolant could be attained. In the boiling state, the values of the heat transfer coefficient (i.e., heating capability to coolant) and heat flux (i.e., heat absorption capability by coolant) were much greater than those in the non-boiling state. The initial water temperature affected the time to initiate bubbles. A diagram of the heat flux against the heat transfer coefficient was created to analyze the heat removal efficiency of water coolant. A slope value of the linear relationship in the diagram can be applied to classify the states of the boiling flow patterns, boiling nucleation, bubble flow, and plug flow.