Thermal Conductivity Apparatus
Theory
The Apparatus follows widely accepted theory of heat conduction in liquids based on Debye’s concept in which the hydroacoustic vibrations (phonons) of a continuous medium(base fluid) are responsible for the heat transfer in liquids. Based on this heat transfer mechanism, Bridgman has obtained a formula, characterized by the direct proportionality between thermal conductivity and sound velocity in pure liquids.
where ν_{s} = ultrasound velocity,
N (Avogadro's number) = 6.02×10^{23} and V (molar volume) =
K_{B}= (Boltzmann's constant) = 1.3807×1023 J/K
For Polyatomic Liquids it was modified as:
For Nanofluids it was further modified by J.Hemalatha as under:
where, k_{bm} is the thermal conductivity value obtained through the modified Bridgman equation, ρnf is the density of nanofluid, and is the molar mass
of nanofluid. x_{bf} and x_{p} are the molar fractions of the base fluid
and nanoparticle respectivelywhereas M_{bf} and M_{p} are the respective molar masses of the base fluid and nanoparticle.
Working Principle
Ultrasound waves of known frequency are produced and its wavelength is measured. Then sound velocity in Liquid
After calculating velocity of sound in Liquid, one can calculate
the thermal conductivity by the formula given by P W Bridgman.
Description
Thermal Conductivity Apparatus consists of following parts: Electronic Unit,Conductivity Cell2MHz,Stability Cell 4MHz to increase settling time of the suspension,Temperature Controller UnitTo maintain temp.of liquids / nanofluids at desired temp from RT to 70°C.
