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 . 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. 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. 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