Reversible Work, Irreversibility, and Exergy (Availability)

Abstract

From thermodynamic point of view, work is considered a macroscopic event, such as raising or lowering a weight or winding or unwinding of a spring. In this, chapter we talk about, which work can be reversible or irreversible and what do we mean by either of these processes.

Problems

Problem 8.1: A pump for a power plant takes in saturated water at 1.5 psi and boosts its pressure to 1500 psi. The pump has an adiabatic efficiency of 0.92. Calculate the irreversibility and the second law efficiency.

Problem 8.2: A power plant uses lake water in the circulating coolant loop. Water enters the loop at 280 K and 100 kPa and exits at 300 K and 90 kPa. If the heat transfer in the loop occurs at 325 K what is the irreversibility?

Problem 8.3: A feed water heater extracts steam from a turbine at 90 psi and 950 °R. It combines the steam with 0.8 lbm/s of liquid at 90 psi and 750 °R. The exhaust is saturated liquid at 90 psi. Determine the second law effectiveness of the heater.

Problem 8.4: A compressor with an adiabatic efficiency of 92 % takes in air at 280 K and 100 kPa and exhausts at 800 kPa. What is (a) the actual work and (b) the reversible work associated with this compressor?