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Old 09-11-2009, 10:40 PM   #1
Drake371
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Default HERMS HEX coil

I have about 25ft of 1/2in SS coiled down to the outside diam of my ball lock keg, my question is how far apart should each coil be?

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Old 09-12-2009, 01:07 AM   #2
JamieT
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Hey Drake!... My coils actually touch.. I don't think there needs to be a significant gap if any at all... It's just extra surface area.. To give you an idea I only used 15ft and I get great results so I think youll be fine if they touch..


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Old 09-12-2009, 01:28 AM   #3
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thanks for the reply, I think I have settles for a ~3/4" gap on mine, wasn't sure what everyone else is using.

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Old 09-12-2009, 03:29 PM   #4
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I would make sure that there is some gap. The increased surface area will improve your heat transfer and improve the system response.
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Old 12-07-2013, 11:48 AM   #5
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Quote:
Originally Posted by GearBeer
I would make sure that there is some gap. The increased surface area will improve your heat transfer and improve the system response.
I agree spacing between the coils of a HERMS setup improves efficiency, but for different reasons. The spacing increases circulation over the coils, not really exposed coil surface area. Theoretically, the contact area between two tangent arcs is zero, but even in practice (unless you have them mashed together) there would be only a nominal increase in surface area with the introduction of space between the coils. Spacing may also reduce heat transfer between the coils.
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Old 12-07-2013, 03:04 PM   #6
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Change "theoretically" to "practically" and I agree with ^ that...

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Old 12-07-2013, 04:26 PM   #7
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There's a tradeoff between good circulation and cramming the coil into the vessel without having to fill it to the very top. Even if you can get a 1/8" gap between coils, it will help when you stir or recirculate the water bath for homogenous temperature.
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Old 12-09-2013, 02:42 PM   #8
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it isn't just surface area, it is flow over that surface area. With the tube squished together, the flow near the surface of the coil will be less, so less heat transfer. Even stirring or recirculating with a pump won't fix it completely. A small gap gives the opportunity for more useful water agitation (plus, more surface area).

I have a stout tanks HLT with their HERMS coil, and I had to make a special recirculation return arm that shoots water down the inside and outside of the coil, to alleviate this problem. I was getting a huge delta in temperature in the HLT even recircing at 10-12 GPM. A coil with gaps will help this problem.
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Old 12-21-2013, 06:17 PM   #9
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Quote:
Originally Posted by BadWolfBrewing View Post
it isn't just surface area, it is flow over that surface area. With the tube squished together, the flow near the surface of the coil will be less, so less heat transfer. Even stirring or recirculating with a pump won't fix it completely. A small gap gives the opportunity for more useful water agitation (plus, more surface area).

I have a stout tanks HLT with their HERMS coil, and I had to make a special recirculation return arm that shoots water down the inside and outside of the coil, to alleviate this problem. I was getting a huge delta in temperature in the HLT even recircing at 10-12 GPM. A coil with gaps will help this problem.
. Wouldn't it have been easier to whirlpool the top recirculating water. Theoretically having the water return in the same downward direction of the coil
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Old 12-23-2013, 02:06 AM   #10
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The coil effectively splits the hlt volume into two zones, inside the coil and outside the coil. Without explicitly shooting the return water into both zones, the water inside the coil was always much cooler that the rest of the fluid. I'm sure this is only a problem for stout tanks tight small coil.


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