Homework Help: Heat transfer question

1. Feb 17, 2008

scar123

Heat does not naturally flow from a cool body to a hot body. A
refrigerator, however, does remove heat from the icebox and expels it as
warm air to the outside world. What is required to make this process
function?

2. Feb 17, 2008

John Creighto

3. Feb 17, 2008

scar123

would conduction be a good answer to this?

4. Feb 17, 2008

John Creighto

Well, obviously without conduction you won't be able to transfer the heat the refrigeration fluid. The rate of conduction depends on the temperature difference. The temperature difference is created because gases cool as they expand.

5. Feb 17, 2008

John Creighto

Well, obviously without conduction you won't be able to transfer the heat the refrigeration fluid. The rate of conduction depends on the temperature difference. The temperature difference is created because the refrigeration fluid cools as it expands.

6. Feb 17, 2008

scar123

So conduction would be the answer to this? WHich is better answer though, Conduction or 2nd law of thermodynamics?

7. Feb 17, 2008

physixguru

The working principle of a refrigerator
Heat is removed from food and the surrounding area, thereby creating an environment which retards the activity of microorganisms. Temperature is usually about 5°C.

A refrigerant is used to remove the heat, i.e., a highly sensitive liquid which converts easily into a gas and back again into a liquid, e.g., freon12 or ammonia.

The refrigerant is carried in tubes at the back of the appliance and around the icebox.

The electric motor activates the compressor in the appliance which forces a gaseous refrigerant in the compressor into the condenser. In the condenser the refrigerant changes into a liquid, heat from the food in the refrigerator is absorbed by the liquid refrigerant and converts it back into a gas, ready for the cycle to begin again. In so doing, the food is cooled.

The refrigerator is thermostatically controlled to ensure an even temperature.

NOW WHAT DO YOU THINK BEST DESCRIBES THIS PROCESS.??????

8. Feb 17, 2008

scar123

Conduction?

9. Feb 18, 2008

physixguru

yupp..........