Advanced Thermal Engineering Test Study

Ideal Otto Cycle

A theoretical thermodynamic model that describes the functioning of a spark-ignition (gasoline) internal combustion engine.

Reversible

A perfect "frictionless" process with no energy losses or turbulence

Enthalpy units

Joules

Otto Cycle Process 1

Isentropic compression: the fluid is compressed adiabatically from the initial volume to the minimum volume

Otto Cycle Process 2

Constant volume heat addition: the working fluid absorbs heat at constant volume, raising its temperature

Otto Cycle Process 3

Isentropic expansion: fluid expands while its entropy remains perfectly constant

Adiabatic

Completely insulated from the surroundings with zero heat transfer

Otto Cycle Process 4

Constant volume heat rejection: the system releases heat to its surroundings while its volume remains perfectly fixed

Volume ratio (compression ratio), r

the maximum cylinder volume to the minimum cylinder volume

Specific heat capacity

The amount of energy required to increase the temperature of 1 kg of a substance by 1C

Specific heat at constant pressure, c_p

1.005 kJ/kg K

Specific heat input

Energy added per kilogram

Symbol with over-dot

represents a rate

Specific heat ratio, k

ratio of the specific heat at constant pressure to the specific heat and constant volume

Specific Internal Energy, u

The total energy of a system divided by its mass

vr

relative volume

Temperature definition

Temperature is related to the energy associated with the microscopic motion of particles

Kelvin Scale

Used as it references absolute zero not an arbitrary reference to the freezing temperature of water

Absolute Zero Kelvin

Temperature at which a system has its minimum possible thermal energy. A substance cannot be cooled below this in an ordinary thermodynamic sense between there is no lower thermal energy state available.

Zeroth Law - Thermal Equilibrium

If two systems are each in thermal equilibrium with a third system, they are also in thermal equilibrium with each other

First Law - Conservation of Energy

Energy cannot be created or destroyed, only transferred or converted from one form to another

Second Law - Entropy and direction of processes

The total entropy of an isolated system can never decrease

Third Law - Absolute Zero

As the temperature of a perfect crystal approaches absolute zero, its entropy approaches zero, provided it has a unique ground state