Thermodynamics (first and second laws) in dyeings

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.
Contd…
 The first law of thermodynamics is dealt
with three fundamental concepts namely
“Energy, Work & Heat” and relationship
among them.
Energy
 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=H
products
-H
dyes
∆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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