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Thermodynamics refrigerator problem!

  • #1
Hi Everyone!
I have couple of questions this time! :D

1) In refrigerator we say that we have to do some work on system to flow heat from lower temp body to higher temp reservoir , so if temp1 > temp2

then temp2 + work = temp1 now what i want to ask is that
what kind of work we do on system to absorb heat? e.g we do expansion on system

please tell taking example of pistons , it makes me pretty clear!

2) if we say that reversible process why we say that heat should be flown infinety slowly , no dissipation of enerygy etc??

Thanks a lot for taking your preciuos time for me!!!
 

Answers and Replies

  • #2
please mods move this thread General physics , thanks!!
 
  • #3
Andrew Mason
Science Advisor
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Hi Everyone!
I have couple of questions this time! :D

1) In refrigerator we say that we have to do some work on system to flow heat from lower temp body to higher temp reservoir , so if temp1 > temp2

then temp2 + work = temp1 now what i want to ask is that
what kind of work we do on system to absorb heat? e.g we do expansion on system

please tell taking example of pistons , it makes me pretty clear!
I am not sure what you are asking. No work needs to be done for a system to absorb heat. Heat flows naturally from higher temp. body to a lower temp. body. In a refrigerator, this occurs by compressing a gas (raising its temp. and releasing heat to the hot reservoir) and then letting that compressed gas expand and do work (lowering its temperature and absorbing heat from the cool reservoir).

2) if we say that reversible process why we say that heat should be flown infinety slowly , no dissipation of enerygy etc??
Energy is dissipated in a reversible process. The ideal Carnot engine will dissipate less energy than any other engine, but it will never reach 100% efficiency.

AM
 

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