notes/uni/mmme/1048_thermodynamics_and_fluid_mechanics/thermodynamics.md

---
author: Alvie Rahman
date: \today
title: MMME1048 // Thermodynamics
tags: [ uni, nottingham, mechanical, engineering, mmme1048, thermodynamics ]
---

# What is Thermodynamics?

Thermodynamics deals with the transfer of heat energy and temperature.

# Concepts and Definitions

## System

A region of space, marked off by its boundary.
It contains some matter and the matter inside is what we are investigating.

There are two types of sysems:

- Closed systems

  - Contain a fixed quantity of matter
  - Work and heat cross bounaries
  - Impermeable boundaries, some may be moved
  - Non-flow processes (no transfer of mass)

- Open systems

  - Boundary is imaginary
  - Mass can flow in an out (flow processes)
  - Work and heat transfer can occur

## Equilibrium

The system is in equilibrium if all parts of the system are at the same conditions, such as pressure
and temperature.

The system is not in equilibrium if parts of the system are at different conditions.

#### Adiabatic

A process in which does not cross the system boundary

## Properties of State

*State* is defined as the condition of a system as described by its properties.
The state may be identified by certain observable macroscopic properties.
These properties are the *properties of state* and they always have the same values for a given
state.

A *property* can be defined as any quantity that depends on the *state* of the system and is
independant of the path by which  the system arrived at the given state.
Properties determining the state of a thermodynamic system are referred to as *thermodynamic
properties* of the *state* of the system.

Common properties of state are:

- Temperature
- Pressure
- Mass
- Volume

And these can be determined by simple measurements.
Other properties can be calculated:

- Specific volume
- Density
- Internal energy
- Enthalpy
- Entropy

### Intensive vs Extensive Properties

In thermodynamics we distinguish between *intensive*, *extensive*, and *specific* properties:

- Intensive --- properties which do not depend on mass (e.g. temperature)
- Extensive --- properties which do depend on the mass of substance in a system (e.g. volume)
- Specific (extensive) --- extensive properties which are reduced to unit mass of substance
  (essentially an extensive property divided by mass) (e.g. specific volume)

## Units

Property        | Symbol | Units           | Intensive | Extensive
--------------- | ------ | --------------- | --------- | ---------
Pressure        | p      | Pa              | Yes       |
Temperature     | T      | K               | Yes       |
Volume          | V      | m$^3$           |           | Yes
Mass            | m      | kg              |           | Yes
Specific Volume | $\nu$  | m$^3$ kg$^{-1}$ |  Yes      |
Density         | $\rho$ | kg m$^{-3}$     |  Yes      |
Internal Energy | U      | J               |           | Yes
Entropy         | S      | J K$^{-1}$      |           | Yes
Enthalpy        | H      | J               |           | Yes

## Thermodynamic Processes and Cycles

When a thermodynaic system changes from one state to another it is said to execute a *process*.
An example of a process is expansion (volume increasing).

A *cycle* is a process or series of processes in which the end state is identical to the beginning.
And example of this could be expansion followed by a compression.

### Reversible and Irreversible Proccesses

During reversible processes, the system undergoes a continuous succession of equilibrium states.
Changes in the system can be defined and reversed to restore the intial conditions

All real processes are irreversible but some can be assumed to be reversible, such as controlled
expansion.

### Constant _____ Processes

#### Isothermal

Constant temperature process

#### Isobaric

Constant pressure process

#### Isometric / Isochoric

Constant volume process

## Heat and Work

Heat and Work are different forms of enery transfer.

They are both transient phenomena and systems never possess heat or work.
Both represent energy crossing boundaries when a system undergoes a change of state.

By convention, the transfer of energy into the system from the surroundings is positive.

### Heat

*Heat* is defined as:

> The form of energy that is transferred across the boundary of a system at a given temperature to
> another system at a lower temperature by virtue of the temperature difference between the two

### Work

*Work* is defined as:

$$W = \int\! F \mathrm{d}x$$

(the work, $W$, done by a force, $F$, when the point of application of the force undergoes a
displacement, $\mathrm dx$)

# Process and State Diagrams

Reversible processes are represented by solid lines, and irreversible processes by dashed lines.