The only form of entropy interaction associated with

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rk also). Entropy transfer is recognized at the system boundary as it crosses the boundary, and it represents the entropy gained or lost by a system during a process. The only form of entropy interaction associated with a fixed mass or closed system is heat transfer, and thus the entropy transfer for an adiabatic closed system is zero. Surroundings 1 Heat Transfer Tb = 400 K SYSTEM Q = 500 kJ Q Tb = 1.25 kJ/K Sheat = FIGURE 7–58 Heat transfer is always accompanied by entropy transfer in the amount of Q/T, where T is the boundary temperature. Heat is, in essence, a form of disorganized energy, and some disorganization (entropy) will flow with heat. Heat transfer to a system increases the entropy of that system and thus the level of molecular disorder or randomness, and heat transfer from a system decreases it. In fact, heat rejection is the only way the entropy of a fixed mass can be decreased. The ratio of the heat transfer Q at a location to the absolute temperature T at that location is called the entropy flow or entropy transfer and is expressed as (Fig. 7–58) Entropy transfer by heat transfer: Sheat Q T (T constant) (7–71) The quantity Q/T represents the entropy transfer accompanie...
View Full Document

This document was uploaded on 11/28/2012.

Ask a homework question - tutors are online