Experimental study on the liquid cooling of a test MCM using paraffin slurry

This study investigated the effects of the experimental parameters on the cooling performance of the indirect liquid cooling method using water and paraffin slurry. The experimental parameters are mass fraction of 2.5~7.5%, heat flux of 10~40 W/cm² for the simulated VLSI chips and Reynolds numbers of 5,300~16,000. The apparatus consisted of a test section, paraffin slurry maker, pump, constant temperature baths, flowmeter, etc. The test section contains an in-line, four-row array of 12 heat sources for simulation of a 4×3 multichip module, which were flush mounted on the top wall of a horizontal rectangular channel with an aspect ratio of 0.2. The inlet temperature was 20°C for all experiments. The paraffin slurry size of between 10~40 μm did not change before or after the experiment. The chip surface temperatures for paraffin slurry with a mass fraction of 7.5% were lower by 16°C than those for water when the heat flux is 40 W/cm². The local heat transfer coefficients for the paraffin slurry with a mass fraction of 7.5% were larger by 17~25% than those of water at the first and the fourth row. The local heat transfer coefficients reached a row-number-independent, thermally fully developed value approximately at the third row. The local average Nusselt numbers at the fourth row for paraffin slurry with a mass fraction of 7.5% were larger by 23~29% than those for water. The liquid cooling method using paraffin slurry can be applied for high heat flux cases over 40 W/cm²