Answer: Applying the Entropy Balance: Control VolumesAir

Chapter 6, Problem 107P

(choose chapter or problem)

Air enters a compressor operating at steady state at 1 bar, \(22^{\circ} \mathrm{C}\) with a volumetric flow rate of \(1 \mathrm{\ m}^{3} / \mathrm{min}\) and is compressed to 4 bar, \(177^{\circ} \mathrm{C}\). The power input is 3.5 kW. Employing the ideal gas model and ignoring kinetic and potential energy effects, obtain the following results:

(a) For a control volume enclosing the compressor only, determine the heat transfer rate, in kW, and the change in specific entropy from inlet to exit, in \(\mathrm{kJ} / \mathrm{kg} \cdot \mathrm{K}\). What additional information would be required to evaluate the rate of entropy production?

(b) Calculate the rate of entropy production, in kW/K, for an enlarged control volume enclosing the compressor and a portion of its immediate surroundings so that heat transfer occurs at the ambient temperature, \(22^{\circ} \mathrm{C}\).