The history of boat refrigeration is interesting as more innovative
new designs have failed than were successful. Most of the
refrigeration units designed for light duty in cool climates performed
poorly in warm climates or had major maintenance problems. Diaphragm
membrane oil free compressors driven by 12 volt motors were built by
two different companies in the eighties are all gone by now. Large 12
volt motors with belt and direct shaft driven compressors are a
disappointment do to noise, vibration and motor repairs. Ninety volt
motors driving a refrigeration compressor and powered by special
engine alternator failed to satisfy boaters because of their
electrical problems. Other hermetically sealed 12 volt compressors
motors with brushes from China and Italy were short lived mainly do to
non replaceable brushes wearing out.

There are five new unproven small mobile refrigeration systems
intended for boats that need to be evaluated by in-service experience,
variable speed DC compressors, CO2 refrigerant compressors, multi
voltage solar compressors, Masterflux 12 volt compressor systems and
even 12 volt air conditioning systems.
• Danfoss 12/24 volt variable speed compressors offer true efficiency
because compressor output capacity can be matched to other system
components as well as box size and climate heat load conditions. When
ice boxes were small or evaporators were undersized the old fixed
speed compressors cycled to often over powering evaporators by
exceeding their rate of heat transfer from food contents in
refrigerated box. When one of these new icebox refrigeration
conversion units is purchased the manufacturer will set the
compressor’s speed based on the type of gas, expansion device used and
evaporator temperature. Later it is possible in-service to change
compressor speed to improve efficiency as basic design conditions
change. The new Danfoss BD variable speed compressors are no longer
experimental as they now experienced more than 100,000 hours of
service. There are now at least ten manufacturers building
refrigeration systems for boats using the Danfoss BD35 and BD50
variable speed compressors.
• Carbon Dioxide (CO2) refrigerant is believed to be the replacement
refrigerant for all future high and medium temperature refrigeration
systems. In Europe and Australia there are industrial applications
using reciprocal and radial CO2 compressors now. AvXcel inc. did
produce an icebox conversion linear motor CO2 unit for boats and
demonstrated it at major boat shows. This ice box unit and a 0.88 cu
ft portable unit were sold under the name Tropikool. Tropikool’s units
use a free piston Stirling cooler oil free linear motor. It appears
AvXcel is no longer in business. The small portables are now available
at Wal-Mart under the Colman name.
• Danfoss has a new BD solar powered compressor that can handle a
voltage range from 10 to 45 volts DC. I know of no company building a
system using Danfoss’s solar compressor and module but there is a
complete application guide on their web site for the DIY person or job
shops looking for a new product line.
• Glacier Bay has another unit, the Micro HPS has been around for
three or four years but I know of none in service. I recently received
a question asking about the Micro HSP on this refrigeration forum and
answered it as best I could. I would like to hear from cruisers that
have one of these units in their boat. What I look for is actual
running hours per year and problems experienced with system in actual
warm cruising areas. I talked to a representative of GB about the
Micro unit and they are reorganizing and are not concentrating on boat
refrigeration at this time.
• Twelve volt air conditioning, is it practical on a sailboat? There
are 12 volt AC units developed for the trucking industry but the
performance figures I have seen are unbelievably high. Amp-hrs
consumed at night when boat hull is in seawater temps above 78 degrees
or higher indicates to me these units are not practical. First if air
conditioning is intended for creature comfort removing the moisture
from the air is just as important as cooling the air. Air can be
cooled quickly but dehumidifying air takes hours of system running
time. I sometimes think engineers that live in moderate climates
design refrigeration and AC for only the weather climate they are
familiar with.

I am interested in your comments.

Richard Kollmann wrote in news:2372021d-
:

I am interested in your comments.


Does anyone but me remember Rovax, or some name like that.....??

I read an old Popular Science where Chrysler put 6 fat engineers in a big
Plymouth Sedan with Rovax gas-free, compressed air AC unit in the Mohave
Desert at 124F and with 6 sweaty bodies in lab coats with pocket
protectors stuffed up got it down to 57F in the Plymouth in no time. The
outlet air was near ZERO F!

Of course, then the gas manufacturers got it buried because it used JUST
AIR, sucking air out of the cabin through a muffler to eliminate the
rotary high-volume compressor intake noise, pumping it all the way up to
30-35 PSI and running that HOT AIR from the compression through a
standard-looking oil cooler radiator, then RELEASING the air through the
OTHER SIDE of the rotary compressor, recovering a lot of the energy it
took to compress it.

What came out was frozen air and solid ice crystals. Anaconda made a
metal heat exchanger/ice filter that used this ice to cool the intake
air, making it even more efficient and melting the troublesome ice, and
re-humidifying the released air.

This system was supposed to be the holy grail of the MEAT industry, too,
because the melted water was put BACK into the refridgerated outlet air
so it WOULDN'T DRY OUT THE MEAT in the cooler.....


.......then, as with most inventions that kick some corporation's ass (Dow
Chemical)....it was bought and BURIED....

Feel the air coming out of a tire when you unscrew the valve stem out of
it....COLD.

No exotic gasses....no high compression pumps....no high pressure
lines....30 psi! And, if it leaked....so what? It also had a tire valve
outlet on the cool side of the heat exchanger so you could blow up your
tires with compressed air anywhere!

......then they buried it.....never to be heard from again......

Damn them.....all.

"Richard Kollmann" wrote in message
...
big snip

I am interested in your comments.

You forgot to mention the propane units. Dometic does a good business
selling propane units to the RV market. They seem to work really well even
in hot environments and they don't seem to use excessive amounts of propane.
A 20 pound tank runs their fridge for a couple of weeks according to one
RVer I know.

Some say they don't work too well on boats because they must remain on the
level but most boaters these days stay put much more than they actually
sail. I knew one cruising sailor who used a propane fridge and had the
burner part gimbaled so it would work even when heeled. He ran everything
off propane. Heater, Air Conditioning, Barbeque, fridge, water heater, etc.
He didn't notice it because he was used to it, I guess but there was a
propane smell about his boat. (I know propane doesn't smell but there's a
chemical added to make it smell.

Wilbur Hubbard

Larry, no one suppressed the concept of using compressed air for a
cooling medium. Your basic concept is correct when air is compressed
it generates heat. If warm compressed air is cooled while under
pressure and returned back to ambient air temperature then released
through a narrow orifice this ambient air will expand and the result
will be refrigerated air.

In 1950 when the first aircraft with piston engines were pressurized
by an engine driven compressor extra air from these compressors was
used for air expansion cabin cooling. This hot air was first diverted
to a heat exchanger where outside ram air passing through this
radiator reduced temperature of compressed air. When airplane was on
the ground fans supplied this airflow as long as compressor was
running. In order to lower air temperature interring passenger cabin
to near freezing a secondary heat reduction unit was added called an
air cycle turbine machine and another external ram air heat exchanger
was added. When heat was required instead of cooling hot air could be
bypassed around air conditioning part of system. When aircraft
converted over to jet engines bleed air from engine compressor section
supplied air for heating and AC.

I have no information on any other mobile applications of compressed
air air-conditioning but do know of two were large stationary systems.
On one of these systems I gave testimony in a court case about its
performance. Four large 1200 HP compressors were connected to a
manifold where this warm pressurized air could be used for heating as
is, or it could be diverted to large fan cooled outside air heat
exchangers that removed process heat. This tempered air was not cool
enough to remove moisture so it required additional cooling to provide
low temperature air conditioning.

Because of the large amounts of compressed air and heat removal
requirement of an automobile it is hard to believe that pressurized
air could ever replace the phase change of liquid to gas efficiency
that today’s refrigerants provide.

On Sun, 25 May 2008 10:47:19 -0700 (PDT), Richard Kollmann
wrote:

Larry, no one suppressed the concept of using compressed air for a
cooling medium.

They used it on refrigerated ships long before the freons were even
invented. The arternatives included such hazmat as ammonia, sulfur
dioxide, and [I can see the fireball], propane. Air was the best of a
bad lot, or so many thought. Ammonia is, however, popular today for
really large refrigeration installations.

Casady

In the UK you can get an ELECTROLUX fridge for boats and rvs which will
operate on 12v, 230v or gas. I had one on my last boat and it worked well
even in the Med. I would have another anytime. They consume about 10 Amps on
12v but use very little gas. A 10 lb cylinder will last at least 2 weeks. I
ran mine on 230v in the marina and on gas when at anchor. The rocking of the
boat had no adverse effect on operation, but a long term tilt when motoring
did stop the cooling operating.

They do need a flue but the latest ones have a balanced flue.

Alec


"Wilbur Hubbard" wrote in message
ews.com...

"Richard Kollmann" wrote in message
...
big snip

I am interested in your comments.

You forgot to mention the propane units. Dometic does a good business
selling propane units to the RV market. They seem to work really well even
in hot environments and they don't seem to use excessive amounts of
propane. A 20 pound tank runs their fridge for a couple of weeks according
to one RVer I know.

Some say they don't work too well on boats because they must remain on the
level but most boaters these days stay put much more than they actually
sail. I knew one cruising sailor who used a propane fridge and had the
burner part gimbaled so it would work even when heeled. He ran everything
off propane. Heater, Air Conditioning, Barbeque, fridge, water heater,
etc. He didn't notice it because he was used to it, I guess but there was
a propane smell about his boat. (I know propane doesn't smell but there's
a chemical added to make it smell.

Wilbur Hubbard