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  • bonkysleuth
    bonkysleuth's Avatar
    314 posts since Mar '07
    • 31 Aug `08, 5:51PM

      I came across this question under the "Boiling & Evaporation" Chapter. It says, what is the principle used in the working of a refridgerator?"

       

      My immediate answer would be convection. However, I don't have a clue how convection cuts any link with Boiling and evaporation.

       

      Is there any discrepancies with my answer? (Maybe yes, haha) But, whatever the case, do give your take on this.

       

       

       

      OH. Why is it a room cannot be cooled by turning on a fridge and leaving the door open? Quite worth thinking... I don't really know the exact answer to this, but still... anyone can give it a try.

       

      Thank you.

  • skythewood
    skythewood's Avatar
    4,263 posts since Jul '07
    • 31 Aug `08, 5:54PM

      Convection is correct.

      refrigerator cools by transfering heat out. Since the hot air is transferred into the same room, you can't cool the room

      Same reason the air conditioner cooling unit is outside your house, and not inside.

  • bonkysleuth
    bonkysleuth's Avatar
    314 posts since Mar '07
    • 31 Aug `08, 6:06PM
      Originally posted by skythewood:

      Convection is correct.

      refrigerator cools by transfering heat out. Since the hot air is transferred into the same room, you can't cool the room

      Same reason the air conditioner cooling unit is outside your house, and not inside.


      Yea, thanks. I was thinking that fridge removes heat from inside and pumps hot air outside. Same concept. =D

  • skythewood
    skythewood's Avatar
    4,263 posts since Jul '07
    • 31 Aug `08, 6:22PM

      zzz... so you testing me ah.

      my turn than. go find out at what angle should you throw a ball in order to achieve maximum distance, and use simple vector diagrams to show your working.

      Edited by skythewood 31 Aug `08, 6:23PM
  • Moderator
    eagle
    eagle's Avatar
    17,970 posts since Aug '01
    • 31 Aug `08, 6:52PM
      Originally posted by bonkysleuth:


      Yea, thanks. I was thinking that fridge removes heat from inside and pumps hot air outside. Same concept. =D

      I forgot the thing already.... but I think there's something called carnot engine...

  • Twincat
    Twincat's Avatar
    692 posts since Dec '03
  • ditzy
    I are serious cat
    ditzy's Avatar
    49,836 posts since Dec '03
  • maurizio13
    maurizio13's Avatar
    12,343 posts since Sep '06
    • 31 Aug `08, 10:59PM
      Originally posted by ditzy:

      Because what goes up, must come down.icon_lol.gif


      Not exactly true, whatever goes into space will never come down again. icon_lol.gif

       

  • nightzip
    nightzip's Avatar
    5,745 posts since Oct '04
    • 31 Aug `08, 11:40PM

      yup. A fridge uses the radiator at the back of the equipment to radiate heat away from inside the fridge. The heat transfer makes the inside of the fridge cool, but using coolants evaporating at much lesser than boiling point of water, normally coolants evaporates around 5-10degC, that runs through tubes inside the fridge to outside the fridge.

      The heat that is taken off from inside the fridge by the evaporated coolant, then cools down and precipitates back to liquid to flow back. The outside hotter fluid is cooled by fans on the radiators.

      Thus when you open up the fridge, the room will not be cooled, as the front side of the fridge gets cool, but the back side of the fridge gets hot. In fact there is no change in overall temperature of the room. For more advanced part, since there is no 100% efficient systems, most probably, you will get a “hotter” room by opening up the fridge door, as the regulator pumps up the needed electricity to try to cool the whole room at higher temperature than the chamber.

      Same for aircon.

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