Homesteading Refrigerator to Die With –Part 5 – Passively Conducting Heat

Now that we’ve covered the desire to build a well insulated refrigerator and freezer, as well as the advantages associated with living in a cold climate where ice can be produced passively, it’s time to move on to the detail of what a refrigerator system might just look like, and talk abut ways in which the idea can be expanded to improve the performance of actively powered freezers.

Two-Phase Thermosiphons (TPTS)

First, we have to talk about the operation and principles of a TPTS, and the difference with a Heat Pipe.  Both of these devices are forms of heat conductors.  Heat naturally flows from regions of a higher temperature to regions of a lower temperature.  Metals are a common choice for this- copper and aluminum being two of the more commonly selected, although other metals can be used depending on the environmental conditions present.  Metals are well known as effective conductors of heat, but the larger the distance between the heat source and heat sink, the larger the temperature difference necessary in order to conduct a given heat load.  Many applications, such as the cooling of integrated computer chips, require the lowest temperatures practicable at the source of heat, and the distance to the heat sink can be a few centimeters, to even more than a meter away.  Metals alone are not always suitable, so other methods have been developed.

Counterflow TPTS

A sealed metal pipe (assumed copper from here on out) containing a a volatile refrigerant at saturation, can conduct heat far better than the metal alone.  A simple example would be a one meter copper pipe, sealed with a few grams of  r134a refrigerant inside.  In a slightly vertical orientation, heat applied to the lower end of the pipe will first be absorbed by the copper, and then conducted to the the liquid refrigerant that naturally settles there.  Some of the liquid evaporates, raising the internal pressure of the pipe.  Refrigerant vapor higher up in the pipe, now at a higher pressure, will warm to a temperature slightly greater than the copper walls which are cooler than are found below where the heat is applied.  The copper walls absorb some latent heat, and the vapor is condensed, falling by gravity back to the bottom, where it can pick up heat and begin the process again.  Localized pressure differences between the heating region and the cooling region cause vapor to move from hotter to colder areas.  The more of the un-heated pipe which is exposed to the ambient air, the lower the temperature it will reach, and the lower the overall pressure the pipe will reach.  If only the top few centimeters are to dissipate heat (the condenser), the middle section can be insulated, such that very limited heat is dissipated in this region (or adiabatic region).  By adding additional heat exchange surface area to the condenser end, passing air or another cooling fluid across it, the heat source can be held at a lower temperature than it otherwise would without the additional design features.  Also, the surface area of the heat source region (or evaporator) can be improved with added fins, and increased internal surface area- conducting heat into the liquid more effectively and with a smaller temperature difference.

The device is a Counterflow Two-Phase Thermosiphon.  Two phases (vapor up and liquid down) flow in opposite directions in a common pipework.  They can interact with one another, impeding smooth flow, and increasing the temperature difference (delta T) the device operates at for a given heat load and operating conditions.  Gravity is essential for good operation, and is why these are sometimes referred to as Gravity Assisted Heat Pipes.  They only work if the condenser region is Read more ›

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Posted in Refrigeration, Refrigerator

Homesteading Refrigerator to Die With –Part 4– The Scott Nielsen Ice Refrigerator

Article from “Rodale’s New Shelter”, July-August, 1981

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Up Next

We’ll be getting into the design considerations of two-phase thermosiphons, building a passive refrigerator, and other opportunities with having freeze ice.

Homesteading Refrigerator to Die With –Part 5– Passively Conducting Heat

-M.C. Pletcher

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Posted in The Squatch

Homesteading Refrigerator to Die With –Part 3– Passive Winter Ice

In the late 19th century, and first half of the 20th, ice refrigerators were a common feature in American households.  Blocks of ice could be purchased every few days and placed in an insulated box to slow the decay of foodstuffs.  The length of time between new blocks varied according to the size of the block, ambient conditions, condition and effectiveness of the refrigerator, and the economic access afforded to the household.  By and large, production of ice was first accomplished through the natural winter freezing of lakes and ponds in the northern latitudes, where it would then be scored, cut, and hauled into insulated warehouses and then distributed to customers.  This practice would continue well into the 20th century, but would eventually be supplanted by the mechanical production of ice with vapor compression or absorption machines, then altogether with the advent of affordable domestic mechanical refrigerators.  Very few individuals still utilize ice to for everyday home refrigeration needs.

Advantages to Living in a Cold Climate

As a means to provide home refrigeration without the assistance of industry, harvesting naturally produced ice in the winter, and using it throughout the year is certainly an option, but the region of southwestern Pennsylvania I am from doesn’t typically get cold enough, or for long enough, to freeze bodies of water to a thickness where sizable blocks could be cut.  An insulated storeroom would have to be of a size to hold a years worth of ice.  Also, there is the potential issue of refrigerator temperatures peaking higher than the target temperature of 4 degrees C.  Ice typically melts around 0 degrees, so such a small temperature difference would have to be maintained with ample refrigerator insulation, and well designed air circulation.

Nonetheless, some of these problems are solvable by looking at the problem with fresh eyes.  I believe there are great opportunities that come with low outdoor temperatures for a few months out of the year.  Dissipating latent heat from a substance like water, and in large enough quantities, then storing the “charged” phase change material, can have the effect of caching cold wintry conditions where food keeps longer, for use in high ambient conditions when it doesn’t.  Furthermore, this “ice bank” could drastically improve the performance of mechanical refrigeration systems as the discharge heat of these machines would be very effectively cooled by ice, only to later be dissipated to cold winter air.  Essentially, we’re talking about temporal heat displacement for refrigeration.

Examples of Prior Work

Natural ice harvesting was described above, and represents the best (and most developed) example of this, but we’re going to move beyond that.

Various studies, and actual installations have been performed to establish effective ways to offset annual heating and cooling loads on homes and commercial buildings.  These typically include a reversible heat pump which extracts latent heat from water to make ice and heat the building in the winter, then dump heat into the ice bank in the summer for better overall energy economy.  One of the first such studies I read was done by the Oak Ridge National Laboratory in the late 70s.  This is one of the papers produced.  Several large commercial buildings produce ice during night-time hours when outdoor temperatures are lower and electric rates are cheaper, in order to provide lower cost air conditioning during the day.  These systems are not passive, although there may be some that incorporate passive features.

A very simple example of domestic refrigeration was done in Essex Vermont.  I know of two such installations:  one was a refrigerated store room, and the other a freezer.  These are largely passive systems in that they do not actively pump heat, but instead freeze a large ice bank of plastic bottles with the frigid New England winter air.  Read more ›

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Homesteading Refrigerator to Die With –Part 2– Insulating to Decrease Load

In an effort to reduce the power consumption of a stand-alone domestic refrigerator an upright freezer, I will be adding additional insulation to standard units.  A large amount of the heat gain (and thus heat to be pumped out), leaks through the walls of the cabinet.  Another great source of heat load is air leakage around the doors, so quality seals are a must.

Insulation

Insulation types have changed greatly over the years, from horse hair, charcoal, cardboard, rockwool, cork, fiberglass, to to the standard today:  urethane blown foam.  Although it could be fun and beautiful to build a cabinet from scratch, this is a project for another time.  Manufactured cabinets are so incredibly common, people pay to get rid of them, so I might as well use this as a good sealing core to my fridge and freezer, and insulate around that.  I could build a large wooden box, finish the outside with tongue and groove with trim, support the core cabinet in the center of the box, and blow in an expanding foam around it, but I’d prefer to avoid nasty (and messy!) substances like these.  Instead, mineral wool bats or thick sheets will be strategically placed over the top, bottom, back and sides.  The sides, top and bottom should extend out a few centimeters to account for the recess of the door.

Likely an ice refrigerator from the early 20th century

Door

The door itself will be insulated similarly to the cabinet, fully enclosing it with mineral wool, or perhaps a foam board.  The face of the door is finished with wood in the same style as the cabinet.  The nature of the recessed door won’t allow Read more ›

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Homesteading Refrigerator to Die With – Part 1 – Background and Selection

This is a proposal for a refrigeration system which is intended to eliminate the need for electricity as much as possible.  What follows is my refrigerator and freezer; it is not for everyone, and it is not designed for commercial sale.  I have no such aspirations to patent or in anyway restrict the free application of my ideas.  Potentially, if a favorable method of low energy cold storage is found, I might manufacture and sell components or custom installations, but this is not the impetus for my efforts.  This is purely a work of passion and a long time desire to create refrigeration capacity outside the paradigm of fleeting cheap energy.  Society is far too complex and interconnected, with the technology that supposedly freed us from drudgery, has instead taken on a life and evolutionary path of it’s own, leaving our roll as the biologic hosts, and committing us towards a path of diminished autonomy, guaranteed collapse, and potential extinction.

I’ll be discussing methods to lower the energy consumption of standard refrigerator freezers, the use of passive seasonal ice to offset heat load, two-phase thermosiphons to conduct heat, slurry ice generation, thermal ejector refrigeration, wood fired absorption refrigeration, and perhaps a few more topics.

Background

With the exception of being applied in a slightly novel and conceivably original way, none of these ideas are truly new in the sense that they were pulled from thin air.  Quite the contrary, they come from the study of refrigeration technologies as they go back two centuries and beyond, where their application made economic sense given the resource limitations at that time.  Although I wish to build these things and demonstrate their effectiveness, I realize they will take years of experimentation and hard-won knowledge that only comes from empiricism.

I also know there are a handful of low-tech enthusiasts that would appreciate a discussion of alternatives to a store bought refrigerator, as the model of industrial manufacturing only provides temporary nutritional advantages, setting us up for a rough withdrawal when the bottom of the fossil fuel bucket is scraped clean, and a handful of people at present want to cut ties with the technosphere.  Any individual interested in these concepts is encouraged to experiment with them and contact me in regards to collaboration.  Much of what follows requires a level of expertise which I do not yet possess, but I have built enough devices along these lines that I feel the problems can be solved.  Many of the designs are kept technically simple and largely avoid controls and valves as we progress.  These I feel, can be approached by a refrigeration novice with a desire to do some research and put the time in.  There are a range of projects that get progressively more complex in the sense that the optimum operational target gets smaller and farther away, so it will only come with patience and practice.  There are a handful of concepts that generally follow a theme, mixed and matched, they form several possible scenarios  that depend on site specific characteristics and practical limitations of size and space available.

Energy consumption per unit of refrigeration (efficiency) is not necessarily the ultimate goal.  Instead, passive systems are sought wherever possible, and when active energy inputs are required, low grade sources are preferred over high exergy electricity.  Some of the initial work will in fact use electrically powered compressors, but Read more ›

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Posted in Philosophy, Refrigeration, Refrigerator

When Hell Freezes Over – Risks and Rewards of Refrigeration

You’re god damn lucky. You really are. Out of all of the hominids born in the last few million years, you were born at a time of abundant energy and refrigeration. Yes, refrigeration – and on top of that, you were born into a society geographically situated and historically fortunate to be disproportionately wealthy, and actually have access to refrigeration. Most people take a technology like refrigeration for granted, not considering the profound ways in which it has altered  what you eat, when you can eat, where it comes from, and ultimately who controls the system that produced it. ‘Artificial cold’ is a blessing to be sure, but it is also a curse. To what degree does refrigeration serve you, and to what degree do you serve refrigeration?  How secure is our food system, and to what is the cost of artificial cold?

Aside from the wealthy aristocrat chilling a beverage, or having his servants concoct a frozen treat, few early 19th century North American inhabitants had any use for refrigeration – why would they be concerned over a problem they aren’t even cognizant of? People would have been getting along fine, more or less, utilizing traditional methods to grow, harvest, prepare, cook, and preserve foods. Certainly, a few individuals made use of ice harvested in winter lakes to help transport perishables to market, but generally speaking, the ice industry would require decades to mature, and to the early observers, success was not guaranteed.

A man by the name of Frederic Tudor got the hair-brained idea to ship ice, harvested in the northeast, to ports in southern latitudes.  The frozen water was to serve as ballast on a ships southern route, the ice would be sold to individuals or businesses unaccustomed to such things, and the ship would return laden with cargo destined for northeastern ports.  The enterprise was initially an abject failure, as he had no place to store the ice once arrived in port, which wasn’t the dilemma it sounds like because little to no ice would survive the trip. However, with perseverance, better insulation techniques, improved harvesting methods, and the establishment of a viable ice market, Tudor found success, even if he was constantly plagued with financial woes.

Long distance and international transport of ice would ultimately pale in size against the domestic market within the United States.  Almost every food would be affected by ice and refrigeration: dairy, beef, hog, chicken, fish, produce, and even beer. In the 20th century, refrigeration technology would change the homes we live in, where they are located, the commercial structures we do business in, and make possible all sorts of industrial processes.

Over the span of a century or so, refrigeration became an inextricable linchpin in our food system. No longer would people be limited to the produce available in their geographic region. Shipped from far and wide, stored in warehouse cold rooms, these foods were shifted temporally by making them available out of growing season, their ripening and decay artificially prolonged by the colds tempering of the bacteria on and within the skins. Grown on larger and more consolidated plots of land, where fruits and vegetables could be cultivated in more ideal conditions, then transported from afar to the market with the greatest demand, and at the greatest profit. Railroads crisscrossed the nation, and new communication systems helped to ensure a timely and efficient delivery. This bounty was now obtainable by a citizenry of new urbanites, wealthier perhaps than their forebears, packed into dense, sprawling cities, they were participants in the burgeoning market economy, and participate they did. All the while they became distanced from the source of their food, more commodity than sustenance.

The beef industry changed too. At one time, it was far less consolidated than we find today, as cattlemen had to drive their herds into the cities where they would be slaughtered for hasty consumption. Live cattle could be transported via rail, but at considerable expense, so dismemberment and curing was another practice as well. Growing cities could no longer burden themselves with the foul smells, and unsanitary detritus of slaughterhouses feeding millions of urban dwellers. Iced railcars and cold rooms would change all of this. Now ranches with thousands of cattle could be fattened on mid-west grain, butchered, chilled on ice, then shipped off to markets countrywide. Monopolistic tendencies were quick to rear themselves with beef barons joining the ranks of the fabulously wealthy and powerful.
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Posted in Personal, Philosophy, Refrigeration, Refrigerator

It’s Evolution Stupid!

The recognition of one’s own ignorance is a valuable component in the character of the individuals I care to correspond and share personal time with. In a world of “leaders” and followers, politicians and prophets, “experts” and arm-chair economic theorists, positioning yourself as ignorant won’t do much in the way of establishing credence amongst your fellow travellers on the ship of so called Progress. People are constantly looking for answers to seemingly urgent issues regarding the economy, government, and the environment, yet the questions we are able (or politely willing) to ask are so often curtailed by the base assumptions of the (increasingly homogenized) culture, and our steadfast determination that we are in control of our own lives. For all the bad blood in the world, the eons of fighting and conquest, revolts and reforms, as well as the advancements in the sciences, so few people are comfortable discussing (if even cognizant of) the role to which technology plays in almost every facet of our lives.

Our technology defines the way in which we affect the world at large, and affect each other, but this works both ways, and the encroachment upon our much prized free-will isn’t always apparent; suppose 7.6 billion of us were ignorant of the air we breathe, which by the way is being considerably altered by our technology. In fact it would be an arduous task to find a place on the surface of Earth untouched by the chain saw, the plow, the paver, the fishing trawler, or the fine particulates to heaps of plastic refuse cast upon the soil and sea.

Much debate surrounds the future of human kind and the habitability of life on Earth, with great emphasis on the all-important technology that will rescue us at our final hour.

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Posted in Organized Entropy Expansion, Personal, Philosophy

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