ParanoidAndroid
Well-Known Member
The majority of people here seem to use the Reflectix wrap for their mash tun insulation (me included). Since we are only trying to keep a liquid at ~155 degrees for 60 minutes or so, a few wraps with that stuff seems to do the job with just a couple degrees of drop. So, if this works for you (or if you use a sleeping bag), then no need to continue as this post is definitely overkill. But I find this stuff interesting, so I'd like to discuss/learn/investigate it more.
Heat transfer can be categorized in 3 ways: Radiant, Conductive, and Convective. Radiant heat is heat transfer across a space by non-contact. Conductive heat is transferred through materials. Convective heat is the transfer of heat through the movement of air.
The Reflectix wrap is designed for radiant heat, and therefore requires an air gap in between the MT and the insulation to perform the way it was intended. Most people don't do this and just wrap it tight with tape or velcro. What we should be focusing on is conductive heat.
In looking at various insulation I came across Closed Cell Elastomeric Foam. This is the material that some pipes are wrapped in (the long black wrap with a slit in them) and some form of it is readily available at Home Depot or Lowes. Obviously you cant wrap that around your MT so sheets are needed and these aren't available through retail. I did find some various brands online though. There are different materials used in the making of these which include:
-Neoprene
-ECH (Epichlorohydrin)
-EDPM (Ethylene Propylen Dien Monomer)
-Latex/Natural Rubber
-NBR Based (Buta-N or Nitrile)
-PVC
-SBR (Styrene Butadiene Rubber)
-Vinyl Nitrile
Like everything else, each has its strengths and weaknesses. They all seem to have about the same k-factor of 0.25 Btu in/fl² hr °F @ 75 Deg F. Some a little higher, and some a little lower. The k-factor of a material is the thermal conductivity, or the measure of a material's ability to transfer heat. Its related to the more popular R-value by taking the thickness of the material and dividing by k, for flat insulation. For tubular insulation its a different formula where an Equivalent Thickness is used comprising of an inner and outer diameter. I'm not sure how our "closed cylindrical vessel" or "semi-closed rigid tank" R-Value would be calculated, so Ill just go with the flat roll calculations, even though its likely wrong.
These sheets come in thicknesses of anywhere from 1/16 inch to 2+ inches. So a 1 inch sheet would have an R-value of about 4, while a 3/4 inch sheet would have an R-value of about 3.
Reflectix claims to have an R-Value of 6.1. Considering R-Value is based on Conductive heat and not Radiant, this is bogus. There is a message board discussion from a couple of years ago that went into detail about this. The conclusion was that, when installed with the correct air gap (0.75 inches or so) between the Reflectix and the material, the Reflectix provides an R-Value of about 1. Each additional wrap would supply another value of 1. If its right up against the material, then I'm sure the R-Value drops significantly.
In going back to the Closed Cell Foam, I was looking for the following:
-Flexibility
-Not extremely soft
->210 deg F handling
-Non-Toxic
-Microbial agent incorporated since this comes in contact with wort
-Water resistant
-Good price to performance ratio
-Available with non-PSA side (or non adhesive on both sides)
Some brands I found online were:
K-Flex Insul-sheet
-K-Factor of 0.245 @ 75 deg F
-Operating Temperature of -297 to +220
-0% Water Absorption
-2 sided plain face available
-Excellent Flexibility
-$44 for 3' x 4' x 1" sheet
Armacell Armaflex
-K-Factor of 0.25 @ 75 deg F
-Operating Temperature of -297 to +180 (I think they make a higher temp version, but was unable to price it)
-$72 for 3' x 4' x 3/4" sheet
Nomaco Flextherm Sheet
-K-Factor of 0.245 @ 75 deg F
-Operating Temperature of -70 to +200
-0% Water Absorption
-Didn't Price
Nomaco Thermacell Sheet (Polyolefin material)
-K-Factor of 0.25 @ 75 deg F
-Operating Temperature of -330 to +210
-Water Vapor Permeability of 0.0 Perm-Inch
-Didn't Price
Aeroflex (EPDM Material)
-K-Factor of 0.245 @ 75 deg F
-Operating Temperature of -70 to +257 deg F
-Water Vapor Permeability of 0.03 Perm-Inch
-Water Absorption of 5%
-$20 for a 3' x 4' x 1" sheet from local supplier
This is a quick list and there are more out there. I'm picking up a sheet of the Aeroflex today. It has a little higher max temperature, but has a slight water absorption. Its cheap, comparatively speaking, and is available now from a local guy. Ill report on results next time I brew.
Does anyone else have any experience with this type of insulation? The instances where this is discussed in a homebrew application are few and far between and/or old.
Heat transfer can be categorized in 3 ways: Radiant, Conductive, and Convective. Radiant heat is heat transfer across a space by non-contact. Conductive heat is transferred through materials. Convective heat is the transfer of heat through the movement of air.
The Reflectix wrap is designed for radiant heat, and therefore requires an air gap in between the MT and the insulation to perform the way it was intended. Most people don't do this and just wrap it tight with tape or velcro. What we should be focusing on is conductive heat.
In looking at various insulation I came across Closed Cell Elastomeric Foam. This is the material that some pipes are wrapped in (the long black wrap with a slit in them) and some form of it is readily available at Home Depot or Lowes. Obviously you cant wrap that around your MT so sheets are needed and these aren't available through retail. I did find some various brands online though. There are different materials used in the making of these which include:
-Neoprene
-ECH (Epichlorohydrin)
-EDPM (Ethylene Propylen Dien Monomer)
-Latex/Natural Rubber
-NBR Based (Buta-N or Nitrile)
-PVC
-SBR (Styrene Butadiene Rubber)
-Vinyl Nitrile
Like everything else, each has its strengths and weaknesses. They all seem to have about the same k-factor of 0.25 Btu in/fl² hr °F @ 75 Deg F. Some a little higher, and some a little lower. The k-factor of a material is the thermal conductivity, or the measure of a material's ability to transfer heat. Its related to the more popular R-value by taking the thickness of the material and dividing by k, for flat insulation. For tubular insulation its a different formula where an Equivalent Thickness is used comprising of an inner and outer diameter. I'm not sure how our "closed cylindrical vessel" or "semi-closed rigid tank" R-Value would be calculated, so Ill just go with the flat roll calculations, even though its likely wrong.
These sheets come in thicknesses of anywhere from 1/16 inch to 2+ inches. So a 1 inch sheet would have an R-value of about 4, while a 3/4 inch sheet would have an R-value of about 3.
Reflectix claims to have an R-Value of 6.1. Considering R-Value is based on Conductive heat and not Radiant, this is bogus. There is a message board discussion from a couple of years ago that went into detail about this. The conclusion was that, when installed with the correct air gap (0.75 inches or so) between the Reflectix and the material, the Reflectix provides an R-Value of about 1. Each additional wrap would supply another value of 1. If its right up against the material, then I'm sure the R-Value drops significantly.
In going back to the Closed Cell Foam, I was looking for the following:
-Flexibility
-Not extremely soft
->210 deg F handling
-Non-Toxic
-Microbial agent incorporated since this comes in contact with wort
-Water resistant
-Good price to performance ratio
-Available with non-PSA side (or non adhesive on both sides)
Some brands I found online were:
K-Flex Insul-sheet
-K-Factor of 0.245 @ 75 deg F
-Operating Temperature of -297 to +220
-0% Water Absorption
-2 sided plain face available
-Excellent Flexibility
-$44 for 3' x 4' x 1" sheet
Armacell Armaflex
-K-Factor of 0.25 @ 75 deg F
-Operating Temperature of -297 to +180 (I think they make a higher temp version, but was unable to price it)
-$72 for 3' x 4' x 3/4" sheet
Nomaco Flextherm Sheet
-K-Factor of 0.245 @ 75 deg F
-Operating Temperature of -70 to +200
-0% Water Absorption
-Didn't Price
Nomaco Thermacell Sheet (Polyolefin material)
-K-Factor of 0.25 @ 75 deg F
-Operating Temperature of -330 to +210
-Water Vapor Permeability of 0.0 Perm-Inch
-Didn't Price
Aeroflex (EPDM Material)
-K-Factor of 0.245 @ 75 deg F
-Operating Temperature of -70 to +257 deg F
-Water Vapor Permeability of 0.03 Perm-Inch
-Water Absorption of 5%
-$20 for a 3' x 4' x 1" sheet from local supplier
This is a quick list and there are more out there. I'm picking up a sheet of the Aeroflex today. It has a little higher max temperature, but has a slight water absorption. Its cheap, comparatively speaking, and is available now from a local guy. Ill report on results next time I brew.
Does anyone else have any experience with this type of insulation? The instances where this is discussed in a homebrew application are few and far between and/or old.