A rigid tank is divided into two equal parts by a partition....

A rigid tank is divided into two equal parts by a partition. One part of the tank contains $4 \mathrm{~kg}$ of compressed liquid water at $200 \mathrm{kPa}$ and $80^{\circ} \mathrm{C}$ and the other side is evacuated. Now the partition is removed, and the water expands to fill the entire tank. If the final pressure in the tank is $40 \mathrm{kPa}$, determine the exergy destroyed during this process. Assume the surroundings to be at $25^{\circ} \mathrm{C}$ and $100 \mathrm{kPa}$.

Key Concepts

Exergy Analysis

Exergy analysis is a thermodynamic tool that assesses the maximum useful work obtainable from a system as it comes to equilibrium with its environment. It quantifies not only energy content but also its quality or work potential, allowing engineers to identify where and how energy degradation occurs during processes.

Exergy Destruction

Exergy destruction refers to the loss of potential to do work as a consequence of irreversibilities in a process, such as friction, viscous dissipation, mixing, and non-equilibrium heat transfer. It quantifies the degradation of energy quality and is directly related to the entropy produced during the process.

Constant Volume Process

A constant volume process, typical in a rigid tank, implies that the system’s volume remains unchanged during the process. This characteristic simplifies the energy analysis since no boundary work is done, and changes in the system’s energy are attributed to heat transfer or changes in internal properties.

Reference Environment

The reference environment, or dead state, is the baseline state of the surroundings (often specified by temperature, pressure, and composition) where the exergy is zero. It is essential in exergy calculations because it defines the conditions against which the system’s available work potential and its degradation are measured.

Irreversible Processes

Irreversible processes are those where entropy is generated, leading to a degradation of available energy that could be converted into work. Understanding irreversibility is crucial in exergy analysis because it directly impacts the efficiency of thermodynamic processes by quantifying the exergy that is destroyed.

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