Oliver, Angelo,
If I use low volt fans (.25 amp) to move more heat out of the condenser area (outside coils) and insulate by one additional inch of urethane foam (reflective foam at home depot) and reflect infrared energy, (silver foil) I can maintain a properly charged
refrigerator with less than 1/4 inch of ice on the evaporator (inside freezer) to 34 degrees at less than 25% humidity at 100 degrees ambient outside temperature.
Heat in and out of an absorption system is an elegant equation, we do not make cold in these machines, we
transfer heat energy out of the food space, ergo we minus the equation on the inside of the
refrigerator by increasing the amount of heat moved on the outside of it.
(I am deliberately avoiding the explanation of the absorption cycle because its a variable of design the operator is stuck with) 
The
insulation added retards the penetration of heat energy thru the wall to the inside, and the
reflective barriers reflects energy that would penetrate thru the
insulation and raise the temp of the food inside.
If you ever drove in a well air conditioned car, and rested your arm on the closed un-tinted window ledge you will know what I am talking about...You must move the arm soon because regardless of the inside temp being cold the arm is hot...Not the air around it...Just the arm.
Food lockers behave the same way, the contents can get warm, then that warms the air in the cold box...There are other sources of heat regarding food such as chemical energy, or humidity that retards efficiency, also behaviors of sugars, and how frequent you access the
refrigerator too,
how thick the ice layer is in the freezer, the thicker the ice the poorer the performance of the evaporator...Finally re-penetration of removed energy,
an issue in trailer design.
Want to survive in the Arctic?
Build a snow house, its -50 outside and +30 inside the snow shelter...Your refrigerator is exactly the same, keep the ice thin in the freezer/evaporator.
I keep ice cream in mine, and its an old one too, I included in the design of the built in cabinet space different technologies to enhance the refrigerator operating universe.
First think of putting a heater in a tiny closet, put a tiny door in the bottom and a small vent in the top...How hot does it get? Would you place your typical food Styrofoam box in that location? Yet its exactly what we do in our refrigerators even today.
The
heat in this space can
re-penetrate the cold box after we worked so hard to get it out?
With
fiberglass trailers of yesteryear in particular we must realize that they are semi clear plastic lenses, the color we see is a several trash bag thick color pigment on the surface.
This pigment is in no way formulated to block U.V.A or B
light, let alone will it even phase
infra red energy (
insensible heat)
insensible heat is by
definition heat that cannot be managed thru a
mechanical process.
Insensible heat must be handled practically two ways...
(1) Don't be there when its there.
(2) Reflect it away.
Insulation delays penetration of this
energy BUT is not as effective as
reflecting it is.
The reason the 12v functions on 3 way refrigerators are not as effective is the input watts on a 12v heating element are
substantially lower, whereas the input b.t.u.s (measure of heat) in the burning of a
propane flame is as high or higher than the 115v element.
Design is not really a thing as owners we have allot to say about after a purchase is made...But we can
increase the heat out of that tiny space the refrigerator is encased in,
limit the available heat to re-penetrate our refrigerator from that space, super insulate the outside of the refrigerator, and line the space with a highly
reflective barrier to send away energy the machine cannot trap or handle. (
insensible infrared heat specifically)
Hope this helps, I try to keep the explanations to a non technical level in a real world sense.
Some promising things are coming in this technology, its exciting to read the research trade zines, the new Danfoss line of compressors solve the losses in power conversions 12v to 115v but are still primitive in still being stubbornly mechanically typical. (reciprocation piston design) I predict a screw or rotary takeover soon which should make the next leap in refrigerant base compression technologies for R.V.s... Next ultra sonic refrigeration will come out of nowhere possibly. Perhaps years farther out the nano tech researchers will trump these techs by the end of my career.
Until then the ammonia absorption system is my best friend.
Happy Camping, Safe Trails.
Harry
Perris Pacer
Scamper
Trailswest Campster
ET-19
1992 Scamp Side bath
Linear Mode
