# Entropy increase in dissipative systems

1. Oct 17, 2009

### Bob S

Consider the following steady-state dissipative system. A mountain stream flowing 1 liter per second drops 100 meters over rocks and boulders, and at the bottom has both a temperature increase and a residual kinetic energy (velocity). The sum of the temperature rise and the kinetic energy is 980 watts. Maximum entropy increase would maximize the temperature rise, but because the stream has kinetic energy at the bottom, the temperature rise is not maximum. If I added rocks to the flow, the system constraints and the temperature rise would be higher. What is the over-riding principle that minimizes the entropy increase (maximizes the kinetic energy), based on the constraints of the system?

2. Oct 23, 2009

### Bob S

In this steady state dissipative system, the additional constraint causes a larger heat dissipation and lower final state kinetic energy. The entropy increase is a minimum, subject to the constraints. I always thought that the entropy increase should be maximal, subject to the constraints. Which is correct?
Bob S

Last edited: Oct 23, 2009