Refrigeration advice needed

Discussion in 'Hardware - PCs, Consoles, Gadgets' started by pensionpointer, Jan 2, 2011.

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  1. Right, not the highest of tech gadgets a fridge freezer but mine is causing some problems in the cold weather. I pay DHE for a quarter with what they call a utility room and I call a corrugated plastic roof over the gap between the house and the garage, with walls and doors.

    Anyway my large Beko fridge freeezer, which won't fit in the kitchen, seems to defrost when the temperature in the room drops into the minuses for any period of a day or two. My 30 year old electrolux beer fridge in the garage in similar conditions works fine.

    Now the Beko fridge bit seems to work ok, but hard to tell when the utility room is so friggin cold, but the freezer fails. Is this some heat exchange issue or is it just a cheap Turkish piece of white-good junk that cannot cope with a decent British winter? Once the temp picks up into positive figures it seems to refreeze.

    Before you wags out there tell me just to keep the door open, I've tried that but even at -5 in the utility room, food still will not remain frozen solid.

    Any REME refrigeration techs out there?

    uqfegd

    PP
     
  2. Mrs PP said no-one on ARRSE would have a scooby about vrefrigeration. I hate it when she's right!

    uqfegd

    pp
     
  3. You need heat to produce cold. Insulate the coil that should be hot. Simples.
     
  4. alden and jinxy,

    Many thanks.

    UQFEGD

    PP
     
  5. What that jinxy bloke said mate. I am that REME bloke whos done the course. Either heat the room up/inverter coil up somehow to above freezing-or borrow some room in your neighbours fridge/freezer until we get warmer weather cos thats when it'll start working properly again!
     
  6. Sorry, but that's bollocks.
     
  7. Bet i could get his freezer working, whilst you ponder on the theory.
     
  8. fill your boots.
     
  9. £250 an hour are you stumping up the cash?
     
  10. £250 an hour? Who the fuck are you trying to kid?
     
  11. Hay, no money, no honey.
     
  12. Cheaper fridge/freezers have only a single compressor and thermostat, so what happens to the freezer is governed by the fridge temperature. In low ambient temperatures, the fridge will switch off, and so the freezer will gradually come up to ambient temperature.
    You could try leaving the fridge door open with the fridge turned to its coldest setting.
    I'm not an expert by any means, but if it doesn't work you've not lost any money.
     
  13. Refrigeration isn't anywhere close to being a specialist subject of mine, but I'll throw forward a theory...

    Fridges and freezers work by a gas being passed around a circuit. Within the circuit is a stage that compresses the gas into liquid form prior to squirting it through a small hole (affectionately known as an orifice). As the liquid emerges from the hole, the change in pressure causes it to return to gaseous state, essentially evaporating. Evaporating liquids causes chilling (a similar process occurs with a canvas water bucket left in the breeze - the water inside chills as the wetness on the outside evaporates).

    The gas (refrigerant) will have been selected to match the required chilling when in a particular range of ambient temperature. If the ambient temperature falls below the designed-for range, the ability of the gas to chill will be adversely affected - it can't evaporate, so doesn't cool down.

    If you have a fridge that's working and a fridge/freezer that isn't, you could try standing them back to back with a blanket or similar covering the gap between them. The heat given off at the back of the fridge may warm the back of the freezer sufficiently to get the freezer's refrigerant condensing again.

    Doubtless somebody with some proper knowledge will either pat me on the back or advise that I'm spouting bollocks...
     
  14. I wouldn't say that was bollocks, more like the Curate's egg - good in parts.

    Think of a fridge as a circular system, with four major components, a compressor at 9 O'clock, a condenser at 12 (this is the grille-like bit you can see at the back of the thing), the expansion device (orifice/tev/whatever) at 3, and the evaporator (the coils inside the fridge) at 6. From 9 to 3 is the high pressure side, and from 3 to 9 is the low pressure side. From 12 to 6 is the liquid side, and from 6 to 12 is the gas side. The liquid leaving the condenser is sub-cooled (i.e. at a temperature lower than boiling point for that liquid at that pressure) and the gas leaving the evaporator is super-heated (i.e. at a temperature higher than boiling point for that liquid at that pressure). The pressures and temperatures are inter-dependant, and the degrees of sub-cooling and super-heat are important to the correct operation of the equipment.

    Now then, if the ambient temperature in the garage is too cold for a particular fridge, this will result in excessive sub-cooling of the liquid in the condenser. This in turn will lead to a lower pressure (refer to an adiabatic expansion curve diagram if you wish to understand exactly why) on the HP side. This will lead to a reduction in the flow through the expansion device, leading to a reduction in the amount of heat picked up in the evaporator (the inside of the fridge).

    However, the same symptoms will be present if the fridge is under-charged (i.e. it has lost some of the refrigerant gas), and there are other problems which will give similar results.