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How do I calculate the void space in a column?

Q: How do I calculate the void space in a column? Actually we are putting ½-inch balls in a 14-inch pipe. Height of packing will be 3 inches. Above the ½-inch balls we will put ¼-inch balls and the packing height will be the same (3 inches). How many balls can I put in the column?

A: A packed bed makeup of a perfectly spherical shape always has a void space of 40%. Void space is greater where the sphere contacts the pipe wall.  I am sure that Dr. Hassan Niknafs of  Saint-Gobain Hassan.Niknafs@saint-gobain.com  can provide you the information you need because his company manufactures and sells balls and pellets for packed beds.

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