- #1

reh

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## Homework Statement

Im working on the following problem and could need some help in answering them:

Work is being produced from a cycle. In order to produce this work, energy is being taking from a high temperature sources at a ratio of 1000 kJ/kg and the extra energy is being deliver to a cold source in a ratio of 500 kJ/kg, the low temperature reservoir is 250 K. a) What is the maximum temperature that the high temperature source could be? b) What is the change in entropy of the system?

## Homework Equations

## The Attempt at a Solution

a) I assume that the system consist of the both heat sources and the device/engine. The total entropy in any process is always:

ΔStotal ≥ 0 where equality holds only for a reversible process.

The entropy change for the sorroundings is 0, because only work is done on the sourrundings, and the entropy change for the device is 0 because the process in the device is cyclical. The entropy change is then:

ΔStotal = -q

_{H}/T

_{H}+ q

_{L}/T

_{L}≥ 0

Rearranging to get the Temperature at the highest source:

T

_{H}≥ T

_{L}* q

_{H}/ q

_{L}

where T

_{H}= T

_{L}* q

_{H}/ q

_{L}if the cycle is reversible and

T

_{H}> T

_{L}* q

_{H}/ q

_{L}if it is irreversible. but then it would have to maximum value?

b)

For Reversible process the entropy change for the system would be 0, and if T

_{H}→∞ then the maximum entropy that can be made in the system is ΔS = q

_{L}/T

_{L}?