Primary Elements of Engineering Thermodynamics

P M V SubbaraoProfessor

Mechanical Engineering Department

I I T Delhi

The First step to Develop Engineering Skills…..

The Main Goal of Engineering Thermodynamics

• Creation of engineering solutions to extrasomaic needs of human.

• Engineering skill demands identification of a specific target in the universe to create these solutions.

• Target identification is the first step in ET.

• Correct Identification of target leads to major success in ET.

Aim: Harvesting of Power from WindEngineering Solution : Development of Wind mill with a specified

Horse Power What is the Precise Target ?

Wind Turbine in an Open Air

The Part of the Wind Which Interacts with Wind Turbine

Identifying Your Target For Better Understanding

A Thermodynamic System

A thermodynamic system is a collection of matter which has distinct boundaries.OR

A real or imaginary portion of universe which has distinct boundaries is called system.OR

A thermodynamic system is that part of universe which is under thermodynamic study.

Thermodynamic System and SurroundingsSystem: the material in a portion of space whose

thermodynamic study is to be made

Surroundings: Everything exterior to the system

Boundary: A separator, real or imaginary, between system and surroundings.

Classification of Thermodynamic Systems

• Basis: Nature of interaction with its surroundings.

• Mass interactions.

• Momentum & Energy Interactions.

• Species Interactions.

Nature of Thermodynamic System : Control Mass

Control Mass (Closed system): fixed mass (solid or fluid) within the boundary:

Mass neither enter or nor leave the boundary.

Volume of the system can change.

Both work and heat can cross the boundary.

Nature of Thermodynamic System : Control Volume

Control Volume(Open (flow) system): A volume with partly solid boundaries and imaginary boundary sections through which fluid moves

Cold air in

Hot air out

Electric power in

Heat loss

Classification based on Momentum Interactions….Also facilitate Energy transactions ….

Nature of Thermodynamic System : Isolated system

Isolated system: An isolated system is one that is not influenced in any way by the surroundings.

A Control Mass through which no heat interactions and which does no work interactions (rigid).

This means that no mass, heat, or work cross the boundary of the system.

James Watt’s Contribution to Steam Engine Development : 1769

Adiabatic Control Mass

Adiabatic Control Mass : A control mass, which is expected to have no heat interactions with surroundings but can do other actions equivalent to work.

Adiabatic control volume

A Control Volume which is expected have no heat interactions, but can have work interactions.

First Level of Knowledge about System : Substance & Purity

• Matter: Distinct chemical species.

– single component – pure substance

– two components – binary system

• A pure substance can become a binary system:

– example: water or steam under normal conditions is a single component; but at very high temperatures, H2O dissociates and becomes a two-component system – the components are H and O (binary)

• A binary system can be treated as a single component:

– O2 and N2 in air under normal conditions can be considered as a single component, “air”.

• Multi-component systems: three or more interacting chemical species