Thermal Equilibrium: Conditions and Application

[tme92]

Can one say a body which has the conditions above mentioned be in thermal equilibrium? How does one apply the definition of temperature equilibrium to this situation?

(Physically I think it's possible for a body to be in this situation if some part of it receives heat from the outside and another loses heat)

 

[Petr Mugver]

Interesting question. I guess it's a matter of what you mean by thermal equilibrium. In many textbooks they say thermal equilibrium is when the macroscopic state variables (temperature, pressure, density,...) of the system are constant over time. In this sense you can say that your system is at equilibrium. But if you consider the whole isolated system your subsystem belongs to, this is not at equilibrium. The flow of heat between all the parts of the isolated system cannot be steady forever, but will forcefully vary over time, and finally vanish when all the parts of the complete system will be at the same temperature (this because an infinite heat reservoir doesn't exist).

 

[Andy Resnick]

Can one say a body which has the conditions above mentioned be in thermal equilibrium? How does one apply the definition of temperature equilibrium to this situation?

(Physically I think it's possible for a body to be in this situation if some part of it receives heat from the outside and another loses heat)

The body is not in equilibrium, but may have steady-state conditions. Our bodies have these conditions: core temperature 98.6 F, skin temperature closer to ambient air temperature.

All this means is that there is a steady flow of heat, and T(x,t) = T(x).