Bangladesh Army University Of Engineering & Technology

A presentation on

“ Basic Thermodynamics Cycle”Presented By:

A. S. M Muhtasim Fuad SohanDepartment Of EEE Student ID: 151061

What is Thermodynamics ?

Thermodynamics is a branch of physics concerned with heat and temperature and

their relation to energy and work. It defines macroscopic variables, such as

internal energy, entropy, and pressure, that partly describe a body of matter or radiation. It states that the behavior of those variables

is subject to general constraints, that are common to all materials, beyond the peculiar

properties of particular materials. These general constraints are expressed in the four

laws of thermodynamics.

“Basic Thermodynamics Cycle

Isobaric process: occurs at constant pressure

Isochoric process: occurs at constant volume (also called isometric/isovolumetric)

Isothermal process: occurs at a constant temperature

Adiabatic process: occurs without loss or gain of energy as heat

“o Isentropic process: a reversible adiabatic process occurs at a

constant entropy, but is a fictional idealization. Conceptually it is possible to actually physically conduct a process that keeps the entropy of the system constant, allowing systematically controlled removal of heat, by conduction to a cooler body, to compensate for entropy produced within the system by irreversible work done on the system. Such isentropic conduct of a process seems called for when the entropy of the system is considered as an independent variable, as for example when the internal energy is considered as a function of the entropy and volume of the system, the natural variables of the internal energy as studied by Gibbs.

“

“Isenthalpic process: occurs at a constant

enthalpy

Isolated process: no matter or energy

(neither as work nor as heat) is transferred into

or out of the system

“

A thermodynamic cycle is a series of thermodynamic processes which returns a system to its initial state. Properties depend only on the thermodynamic state and thus do not change over a cycle. Variables such as heat and work are not zero over a cycle, but rather depend on the process. The first law of thermodynamics dictates that the net heat input is equal to the net work output over any cycle. The repeating nature of the process path allows for continuous operation, making the cycle an important concept in thermodynamics.

Thermodynamic power cycles are the basis for the operation of heat engines, which supply most of the world's electric power and run almost all motor vehicles. Power cycles can be divided according to the type of heat engine they seek to model. The most common cycles that model internal combustion engines are the

Thermodynamic Cycle

Carnot Cycle

Carnot cycle is a reversible cycle where a working fluid goes under a cycle with working process Isothermal heat addition, Icentropic expansion, Isothermal heat rejection and finally Icentropic compression. Carnot cycle has the most efficiency of all the working cycle present in the world because its each process is nearly reversible. Heat Engines work on the Carnot Cycle while Refrigerator and Heat Pumps work on revers Carnot engine.

th Carnot L

H

TT, 1 th net

in

WQ

The Otto cycle efficiency becomes

th OttoTT, 1 1

2

Since process 1-2 is isentropic,

1

2 1

1 2

1 11 2

2 1

1

k

k k

T VT V

T VT V r

where the compression ratio is

r = V1/V2 and th Otto kr, 1 1

1

Thermodynamic Cycle

Otto and Diesel Cycle

Engines working on Otto and diesel cycle in an automoblibe although form in a cycle, are not reversible cycle as the working medium changes changes after each cycle. Otto and diesel are much similar to each other except the heat addition process. In otto heat addition is by constant volume process where as in diesel the heat addition is by constant pressure process. These cycles are not as efficient as carnot cycle as process are not reversible

Applications of Thermodynamics

Thermodynamics in common usage in engineering is the study of energy and its various interconversions from one form to another. Thermodynamics has several types of Applications in our daily life: Fossil-fueled steam power plants, Spark-ignition engines and Jet engines .All types of vehicles that we use, cars, motorcycles, trucks, ships, aero planes, and many other types work on the basis of second law of thermodynamics and Carnot Cycle.

No Questions Please our office

Thermodynamics is not the study of heat and work alone. Thermodynamics is the study of the dynamics and behavior of energy and its manifestations. Energy is the only thing that keeps things going. You are energy.You are thermodynamics.

Thank You Everyone.