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Physics/domestic food freezer


QUESTION: I am looking to buy a frost free upright food freezer for the home.
It will go in the garage, which goes below +5 deg C in winter,and down to 0 deg C on some occasions. The previous freezer worked there for 9 years.
 Most suppliers specify an ambient of +10C to +43C to guarantee  efficiency and correct operation.It is not clear what happens below +10C.
My question is,why is the performance worse at lower ambient temperature ? What physically happens ?
   Intuitively,a lower ambient makes it easier to 'keep the cold in'.
 I have asked manufacturers the reasons, but have not had a good technical answer.

ANSWER: Easier, yes...but what's the point?  If your temperature goes below about -5 deg C in winter then you actually need a heater.  Basically, they specify a range where those parts outside won't freeze up when they're too cold, the parts which normally run hot.  So there's no lower limit from a fundamental physics standpoint...just an engineering standpoint of parts failures (in compressors, motors, etc).

---------- FOLLOW-UP ----------

QUESTION: The freezer interior is at -18 C all the time its working - always below the outside temperature. So 'what's the point' is to do this with minimum electricity usage i.e. max efficiency.And to keep working in winter in my garage.
The makers say the efficiency falls when the ambient goes below +10C, and it may(?)fail to work.
 Since the only working parts outside the freezer are the heat exchanger and compressor motor, I suspect the heat exchanger 'overcools' the refrigerant in low ambient temperatures. Maybe it gets too thick to readily be pumped. I still don't know.
 Further comments would be appreciated.

Well, they're wrong if they say the efficiency falls, unless you're right about overcooling the refrigerant.  The "fail to work" part is probably like I said with the motors and moving parts failing...but I don't design motors.  Both of these issues are engineering issues and not issues of fundamental physics, though.  That's not my area of expertise, you should ask an engineer.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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