Thermodynamics (first and second laws) in dyeings

Introduction of first law It is a subject dealt with volume, pressure, temperature, and concentration and with the relationships between them  The first law prediction is however conce

Thermodynamics (first

and second laws)

By Aravin Prince.P, First- M.Tech- Textile Tech,

KCT.

Introduction of first law

 It is a subject dealt with volume, pressure, temperature, and concentration and with the relationships between them

 The first law prediction is however concern only the difference between the “ initial and final states” of the change in the internal energy

 In dyeing is involving with the color physics like which dye is adsorbed from solution by a substrate, but only with the end product

 The first law of thermodynamics is dealt with three fundamental concepts namely

“Energy, Work & Heat” and relationship among them

 Thermodynamics is concerned with “internal energy U” , that is energy acquired by means of the mass and motions of molecules , intermolecular forces and chemical compositions

 The energy equation is

∆ U=U 2 -U 1

Where ,

∆ U= Total energy U1 =Initial value of the internal energy system U2 =Final value of the internal energy system

Work

 Work may be defined as the energy lost from the system other than by heat transfer

 Basically work is known as pressure- volume

or PV work

 Volume change is represent by ∆V , then the work done is given by

W=p ∆V

First law derivation

 The first principle of thermodynamics states that the internal energy E of the system is closed i.e it cannot exchange material with an external environment, it

is defined as follows

∆E=q-w

Q= heat absorbed by the system

W= work done of the system

At the constant volume the work of expansion is zero and so

∆E=q

At constant pressure work is

w=P ∆V Then the heat is equal

∆E+P ∆V Normally the reaction heat in these conditions is given the name

of enthalpy or thermic content (represented by H), then the equ ,

∆H= ∆E+P ∆Vq Thermodynamics reminds us that the enthalpy of a reaction is

∆H=Hproducts-Hdyes

∆H value is –ve = reaction is exothermic

∆H value is +ve = reaction is endothermic

Second law of thermodynamics

 It is defined as a spontaneous process in an isolated system there is an increase in entropy ; the entropy change occurring during the process, ∆S is positive

 Then the equ

dq (rev) dS=

-T Q= heat absorbed

T= Temp of the system

And for irreversible spontaneous process

dq (irrev)

dS >

-T

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