Timeline for Causes of entropy change
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
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| Mar 31, 2018 at 13:46 | comment | added | pglpm | Typos! "microwave" -> "microwave oven", "surface and flux heating" -> "surface and bulk heating". Sorry! | |
| Mar 31, 2018 at 13:37 | comment | added | pglpm | @Chester Miller: Just two comments. 1. Entropy can increase not only via surface heating but also via bulk heating (as it happens in a microwave). 2. It's possible to have a reversible process (no entropy production) with inhomogeneous temperature throughout the system. These two possibilities are contained in the full formula $$\frac{\partial s}{\partial t} \geqslant \nabla\cdot\left(\frac{\boldsymbol{q}}{T}\right) - \frac{Q}{T},$$ valid for a closed system, where $\boldsymbol{q}$ and $Q$ are the surface and flux heating, and the equality holds for reversible processes. | |
| Dec 8, 2016 at 11:51 | vote | accept | user123733 | ||
| Dec 8, 2016 at 11:50 | comment | added | Chet Miller | In the simple situation I described (as well as all other fluid dynamic situations), viscosity causes mechanical energy to be converted into internal energy. You are doing work to deform the fluid, but not getting any mechanical benefit. This is one way by which entropy is generated within a system. The rate of entropy generation is proportional to the square of the deformation rate, and the constant of proportionality is related to the viscosity. | |
| Dec 8, 2016 at 11:36 | comment | added | user123733 | yes I am familiar , the tendency of not to flow | |
| Dec 8, 2016 at 11:33 | comment | added | Chet Miller | Are you familiar with the physical property known as viscosity and, if so, are familiar with the situation in which a fluid (gas or liquid) is sheared between two infinite parallel plates? | |
| Dec 8, 2016 at 5:49 | history | edited | user36790 | CC BY-SA 3.0 |
added 50 characters in body
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| Dec 8, 2016 at 2:17 | comment | added | user123733 | What do you mean by (by irreversibilities, such as vicsous dissipation) . Can you explain it little more | |
| Dec 7, 2016 at 22:05 | history | answered | Chet Miller | CC BY-SA 3.0 |