R22 Discussion Group

On May 23, 2021, at 10:07 AM, Lowe, Rob <rlowe at vt.edu> wrote:

Hi All,

Sea water is 8.55 lbs/gal, or about 2% more dense than fresh water.

All the hydrocarbon liquids are about 10% less dense than fresh water.  But, keep in mind that many of the commonly used fuel gases are vapors at room temperature:
Boiling Point @ Sea Level (deg F)
Methane: -259
Ethane: -128
Propane: -44
Isobutane: 11
n-Butane: 31

All of these materials come from natural gas, which is mostly methane.  The higher molecular weight hydrocarbons are naturally present in varying amounts depending on the natural gas field.  They are more valuable than methane and are usually separated out prior to the methane being sent down the natural gas pipeline.

Note that n-butane is barely a vapor at room temperature.  For this reason, it is not considered a very good stove fuel.  n-Butane is much more valuable as a petrochemical feedstock.  The 1 lb propane cylinders sold in hardware stores contain nearly pure propane (98+ %wt).  But, because propane boils at -44 deg F, the cylinder it is sold in is actually a steel pressure vessel.  This cylinder adds more weight than was saved by using the less dense fuel.  The disposable gas cylinders commonly sold for camping stoves typically contain 80%wt propane and 20%wt isobutane so the stove will operate in cold temperatures.  However, because isobutane and n-butane are chemically similar, they are very difficult to separate.  For this reason, commercial grade isobutane can typically contain 2-6%wt n-butane as a contaminant.  Low grade camp stove fuel tends to contain more n-butane and may not work in your stove on a cold morning.  This camp stove fuel must be sold in a steel pressure vessel, also reducing the weight savings.

Roger Pihlaja
S/V Dynamic Equilibrium

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From: Ric Stott<mailto:ric at stottarchitecture.com>
Sent: Sunday, May 23, 2021 10:24 AM
To: The Rhodes 22 Email List<mailto:rhodes22-list at rhodes22.org>
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Fresh water and salt water are different.

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ROGER PIHLAJA

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