Efficiency and agility of a liquid CO2 cooling system for molten metal systems

In this study investigations on the efficiency and agility of a liquid CO2 cooling system, using expansion bores fed with liquid CO2 by capillary tubes, to form a thermal seal in a magnesium hot runner channel are performed in a test rig. Via temperature measurements the performance of different sets of cooling parameters is tested and cooling rates are identified depended on a varying nozzle geometry. To validate the measurements, the tests are modelled in a thermal simulation study. The applicability of the liquid CO2 cooling was demonstrated for engineering purposes. Adequate process times could be achieved while using a 16 mm diameter as annular gap, which results in cooling rates up to 4.8 ◦C/s. The tests were validated by a simulation model. The simulations illustrate the inner processes of the test rig and the comparison of temperature curves of the cooling process show a good correlation.