DetroiTug's Tug is going together

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Lopez Mike
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Re: DetroiTug's Tug is going together

Post by Lopez Mike » Sun Oct 25, 2020 12:42 am

I've been the route with various portable fridge systems. The best two are absorption cycle heated by propane and the compressor system that Bart suggests.

I used an ordinary RV propane fridge in Baja for several years and it just ran with zero issues. Two cubic feet and used a 20lb. bottle maybe every three weeks.

My present 25' I.C. powered boat has a 12v compressor. You have to get your head down next to it to tell if it is running. Pulls around 4 amps.

To my knowledge no one has heated an absorption cycle with another source of energy other than a flame or an electric heater with one exception. I saw a small RV propane fridge at a goat ranch in the Baja mountains that had a solar collector (Old satellite TV dish with aluminum foil!) that was arranged to focus on the hot end of the absorption tower. The whole fridge was on an old lazy susan turntable and was moved to follow the sun by hand. A couple of gallon jugs of water frozen to hold the cold overnight.

Using steam to heat one end and cold water on the other would probably work until you shut down the boiler for the night. Generating electricity to run either system would be deranged. Incredibly low thermal efficiency.

You could drive an automotive freon compressor from your main engine and have a holding plate in the fridge for overnight storage. Takes a fair bit of power though. If the box is well insulated you could run the compressor for two hours a day and get by overnight. Mostly a freezer operation.

Propane RV fridge powered by solar cells would be O.K. except for needing a battery at night. A compressor unit needs a battery too. No easy answer except getting by with warm beer. An English thing I'm told (grin).
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Re: DetroiTug's Tug is going together

Post by DetroiTug » Wed Oct 28, 2020 4:32 pm

Stop picking on Mr Lucas 😂

Here is some interesting info on how early voyagers dealt with the refrigeration problem.

It’s a familiar story, but that doesn’t make it any less remarkable: a forgotten shipwreck, long ago sunk to the bottom of the sea, holding once-edible treasures like honey, olive oil or wine. Just this summer, a Roman ship was discovered off the coast of Italy that held nearly 200 still-sealed amphorae (an early type of storage container, often ceramic) in its cargo bay. Though food on ships now only catches our attention in stories like these, it once drove the very act of exploration. Long before the days of modern preservation techniques, crewmen had to eat, and they couldn’t count on being able to stop at a friendly island to restock supplies. This week, we’ll take a look at preserved foods aboard ships, and find out how even a humble cabbage can change the course of human history.

In ancient times, like when this Roman ship sailed, voyages were short, and served mainly to take spices or other goods from place to place. Since trips weren’t long and ships often stopped at port, food didn’t have to be preserved to last an indefinite amount of time. Ship stewards kept kegs of salted beef, dried legumes and a fermented fish sauce called garum, which was a popular condiment of the time. These same preservation techniques – salting, drying and fermentation – all came into play during the Age of Exploration.

By the time Columbus’ ships set sail from Spain, for a voyage of indeterminate length, an average ship’s bay might contain honey, hard cheeses, olives, garlic, dried lentils, salted anchovies and barrels upon barrels of beer and wine. While this diet might seem delicious to some of us today, keep in mind what the vast majority of ships were not able to carry: Fresh meat and dairy spoiled easily, and could not be taken along. Likewise with fruit and vegetables, with the exception of dried fruits like raisins. And while it wasn’t unusual for a sailor’s daily ration of beer to be over a gallon, the beer was weak, and only brought because fresh water would grow algae in the wooden tanks below deck.

With a diet like this, it’s no wonder that malnutrition, in all its forms, was a huge problem aboard ships. Scurvy, a disease caused by vitamin C deficiency, killed over 2 million sailors between 1500 and 1800. In 1499, Vasco de Gama lost 116 members of his 170-man crew to the illness; Magellan lost 208 of 230 sailors 20 years later. While it was known to some that consumption of fresh citrus fruit would help the disease, lemons and limes weren’t often taken aboard ships. They were expensive, and, if spoiled, could contaminate the rest of the food supply. It wasn’t until Captain James Cook sailed in the 1760s that a reliable, affordable defense against scurvy was found: sauerkraut. The fermented cabbage could be kept at room temperature for months at a time, and naturally produced enough vitamin C to protect Cook’s crew from the disease. Eventually, lime juice became a daily ration for British sailors, leading to longer, more adventurous voyages and the nickname “Limey,” which endures to this day.

Nowadays we have so many foods that can be kept in different preservation techniques, it makes the necessity of refrigeration almost non-existent. Milk, eggs, bacon, lunchmeat, are unhealthy anyway.

I have a good cooler, for a few days, a gallon milk jug of water frozen solid beforehand will last a few days.

-Ron
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Re: DetroiTug's Tug is going together

Post by Mike Rometer » Wed Oct 28, 2020 5:10 pm

Good grief! You'll all be looking to run Air-con next!

Beer is cool enough if trailed over the side for an hour. :lol:
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Re: DetroiTug's Tug is going together

Post by TriangleTom » Mon Dec 07, 2020 6:55 am

Lopez Mike wrote:
Sun Oct 25, 2020 12:42 am

To my knowledge no one has heated an absorption cycle with another source of energy other than a flame or an electric heater with one exception. I saw a small RV propane fridge at a goat ranch in the Baja mountains that had a solar collector (Old satellite TV dish with aluminum foil!) that was arranged to focus on the hot end of the absorption tower. The whole fridge was on an old lazy susan turntable and was moved to follow the sun by hand. A couple of gallon jugs of water frozen to hold the cold overnight.
Kind of cheating as they use steam as an intermediary, but they were pretty popular in NY for a while. For a while, it was popular in New York City for larger (~25000+ residents) apartment complexes to have their own independent power plants, usually fueled by HFO and driving steam turbines. The waste steam was often used to run an absorption chiller to circulate cold water through the building in the warmer months for purposes of air conditioning, while the warm condensate or exhaust steam was circulated for heating.
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Re: DetroiTug's Tug is going together

Post by fredrosse » Wed Dec 09, 2020 4:36 am

Steam driven absorption heating systems were well evolved and perfected throughout the 20th century. On a steamboat, with relatively high pressure steam available, as well as hot exhaust steam, fairly good refrigeration efficiency could be available. Commercial Absorption chillers used in larger installations typically use steam as the main energy source to run the chiller.

For a steamboat, vapor compression refrigeration (as used in all our automobiles and most building cooling systems) would be the least energy efficient system one could choose, because running the compressor for typical cycles takes far too much steam engine output to run the typical shaft driven compressor. Present day Vapor compression systems need about 1 horsepower to get 1 ton (12,000 BTU per hour) of refrigeration effect.

Another simple refrigeration system, used to great extent in some industrial plants, is "Steam Jet Air Conditioning" This is actually a vapor compression system, where a steam jet ejector acts as a compressor and produces a good vacuum and causes the boil-off of water in the "evaporator" which cools the air conditioned space. The compressed steam ( plus the motive steam used to drive the jet ejector) at a higher pressure of the compressor outlet is then condensed at a higher temperature, what is conventionally called the "condenser" in present day air conditioning systems. The condensed water is then bled back into the evaporator through an expansion valve, same a conventional present day systems. A very small liquid water pump is needed to return the condensed ejector motive steam water to the high pressure boiler, which in our case would be the steamboat boiler.

The beauty of these systems is that they are simple and reliable, having no moving parts whatsoever. The disadvantage is that the steam jet ejector needs quite a bit of motive live steam flow, and the operating pressures in both the condenser and evaporator are quite low. With water as the working fluid, an evaporator operates at 50F, corresponding to the evaporator pressure of 0.2 PSIA, and the "High Pressure" condenser, condensing steam at 100F, operates at 1.0 PSIA. For a 1 ton refrigeration effect the evaporator steam flow is about 12 PPH (pounds per hour), and requires an ejector suction pipe diameter of about 3 inches.
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