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Monday, October 28, 2013

Oil Can Engineering

Edible oil is available in plastic cans. We buy it in cans of capacity of 5 L. We transfer a small quantity at a time from that can to a small container, and replenish its contents as required. A problem with this system is that the oil pours out in an unruly manner. That makes the process messy, and wastes a bit of the oil too.
"See if you can fix this problem" my wife told me. I was home because I was on Diwali vacation. I was glad to have something to do. I had known the problem, having carried out the procedure myself once. I thought about it a bit, and realized that the oil poured out of the can creating a sort of empty space inside the can. The can had to suck in air before it could pour out more oil. That produced a very turbulent flow, waxing and waning, and spilling out in different directions with time. There had to be an inlet for air, so that the oil would pour out in a smooth flow. I burned two small holes in the hollow handle of the can using a heated nail. The fixed oil can looked like this (arrow on the holes).
Then I tilted the mouth of the can over the small container. The oil poured out in an even stream, spilling not one drop outside the container. After filling the small container, I put a piece of adhesive tape over the holes, so that air and bacteria would not enter it.
"That was wonderful" my wife said with a broad smile. "How did you think of it?"
"I must have remembered laws flows of fluids from school or college physics" I said. For those who have not been able to visualize what I have described, I have put the illustration below. The left part shows the unruly spill, and the right part shows the smooth flow after fixing the oil can.