Thermodynamics ER 1050 Overview

Study Notes

A system is a defined quantity of matter or a region in space selected for study.
Surroundings refer to everything outside the system.
A boundary separates the system from its surroundings; it can be fixed, movable, and has no thickness.

Closed Systems
- Known as control mass; contains a fixed amount of mass.
- Mass cannot cross the boundary, but energy (heat or work) can.
Open Systems
- Also known as control volume; both mass and energy can cross boundaries.
- Common in devices involving mass flow like compressors and turbines.
- Control surface can be real or imaginary, and may vary in size and shape.
Isolated Systems
- A special type of closed system where neither energy nor matter can be exchanged with surroundings.

Properties include pressure (P), temperature (T), volume (V), and mass (m), among others.
Properties can be categorized as:
- Intensive properties: Independent of mass (e.g., temperature, pressure).
- Extensive properties: Dependent on size or extent (e.g., total mass, total volume).
- Specific properties: Extensive properties per unit mass (e.g., specific volume, specific total energy).

The continuum assumption treats matter as continuous and homogeneous, ignoring molecular structure.
Applicable when the system size is large compared to molecular spacing.

A state is defined by a set of properties that describe a system's condition; changes in one property alter the state.
An equilibrium state refers to no unbalanced potentials within the system.
Types of equilibrium include thermal, mechanical, phase, and chemical.

A simple compressible system’s state is identified by two independent intensive properties.
For single-phase systems, temperature and specific volume can determine the state, while for multiphase systems, they may be dependent.

A process is a transition from one equilibrium state to another, with a sequence of states representing its path.
Types of thermodynamic processes include:
- Adiabatic: No heat transfer.
- Isothermal: Constant temperature.
- Isobaric: Constant pressure.
- Isochoric: Constant volume.
- Isentropic: Constant entropy.
- Isenthalpic: Constant enthalpy.

In a steady-flow process, fluid properties can vary from point to point within the control volume but remain constant at any fixed point.
Ideal for continuous operation devices like turbines and pumps, while some cyclic devices can still be analyzed under steady-flow conditions with averaged properties.

Heat: Energy transferred due to temperature differences.
Work: Energy transferred through interactions other than heat.
Both heat and work are recognized only during boundary crossing, are path-dependent, and represent energy interaction during processes rather than states.