Coil direction in small dedicated herms

So, on a recent visit to my parents garage, I dug out about 15' of leftover 1/2" copper that had been lying around since my first immersion chiller build.

I figured it would be too short for an HLT style HERMS setup, but could be good for making a small dedicated HERMS in an electric tea kettle running at slightly higher temperatures. These seem to be quite popular in Australia, with a few companies selling these commercially.

The coil I've made sits in a flat bottomed kettle, with about 8' of coils sitting below the water line.

Before I decide on how to lay out the fittings and copper sweat elbows, I'm wondering if the heat transfer efficiency will be effected by what direction the wort flows through the coil.

I doubt that this would be an issue in larger HLT style coils, but i'm dealing with only about 1.5 quarts of hot water here. Since the heating is coming from the base of the kettle, would it make more sense to have the wort enter near the bottom or the top of the coil?

Damn, I knew I should have dropped out of audio engineering and studied real engineering!

If it were a bigger vessel I'd say go from top to bottom (opposite the direction of heat movement), but with that small a volume I can't see it making any difference. What size batches are you going to do?


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I'm not really following with how this coil looks, but here is my advice: I would have the wort-in at the bottom and wort-out at the top. This should push out the air and ensure there are no air pockets (which will improve heat transfer). If you trickle wort in from the top it's possible that you will not fully fill the coil and you'll miss out on some efficiency.