The only form of entropy interaction associated with

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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...
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