I know that a reversible process does more work than an irreversible process and that extra work is turned into heat. But what does that heat do? Does it increase the temperature?
$\begingroup$
$\endgroup$
2
-
$\begingroup$ Heat will manifest itself as rise in the internal energy of the system. The temperature will increase and it'll stay in that state forever since its an isolated system. $\endgroup$– Shah M HasanSep 5, 2018 at 10:00
-
$\begingroup$ This is a case of a non-cyclic device. For a cyclic device, the system must be returned to its initial state by heat transfer from the system. $\endgroup$– Shah M HasanSep 5, 2018 at 10:01
Add a comment
|
3 Answers
$\begingroup$
$\endgroup$
4
The heat is dissipated and lost to the universe forever. This is why it is impossible to create perpetual motion machines.
answered Sep 5, 2018 at 8:22
-
-
1$\begingroup$ @user145010: The heat will increase the temperature of the machine. Objects can still radiate away heat even in a total vacuum. $\endgroup$ Sep 5, 2018 at 8:24
-
$\begingroup$ Isolated systems do not allow for energy transfer across system boundary. So heat will go nowhere but stay in the isolated system. $\endgroup$ Sep 5, 2018 at 9:54
-
$\begingroup$ From a practical standpoint, assuming that the temperature of the heat from an irreversible process is higher than the temperature of the environment, the heat will dissipate into the environment. The amount of heat that is dissipated will remain constant over time (i.e., it's not "lost"), but the temperature of that heat will decrease to match the temperature of the environment (i.e., it will get more and more "spread out"). Also note that in the real world, truly isolated systems do not exist. $\endgroup$ Sep 5, 2018 at 17:54
$\begingroup$
$\endgroup$
The viscous dissipation of mechanical energy that occurs in irreversible processes involving deformation of a fluid is typically referred to as "viscous heat generation." But this is a bit of a misnomer because it is typically manifested as an increase in the internal energy of the system (so it is not, strictly speaking, heat). Of course, this change in internal energy can be reduced (or added to) by transferring heat from (or to) the system to (or from) its surroundings (across the system boundary).
answered Sep 5, 2018 at 11:51
$\begingroup$
$\endgroup$
I think ,in case of an isolated system, the heat will flow from one part of the system to another.After sometime, if the system attains internal equilibrium(themal,mechanical and chemical), no more processes can occur.