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 = ultrasound velocity,
N (Avogadro's number) = 6.02×10^{23} and V (molar volume) =m⁄p &
K= (Boltzmann's constant) = 1.3807×10^{23} J/K
It is modified by J.Hemalatha for nanofluids as under:
where, k_{bm} is the thermal conductivity value obtained through the modified Bridgman equation, ρnf is the density of nanofluid, and M_{nf} = x_{bf}M_{bf} + x_{p}M_{p} is the molar mass of nanofluid. x_{bf} and x_{p} are the molar fractions of the base fluid and nanoparticle respectively whereas 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 Nanofluids
After calculating velocity of sound in Nanofluid, one can calculate the thermal conductivity by the formula give above by Bridgman. Error in results is found less than 3%.
DESCRIPTION
Thermal Conductivity Apparatus consists of following parts: Electronic unit, Conductivity Cell 2MHz, Stability Cell 4MHz to increase settling time of the suspension, Temperature Controller Unit  To maintain temperature of nanofluids at desired temp from RT to 90°C
Graphical Representation/Diagram
Courtesy R.R. Yadav
References of Papers using our Instrument
 A NOVEL ULTRASONIC APPROACH TO DETERMINE THERMAL CONDUCTIVITY IN CuO– ETHYLENE GLYCOL NANOFLUIDS; M. Nabeel Rashin, J. Hemalatha; Journal of Molecular Liquids; Volume 197, September 2014, Pages 257–262
 A COMPARATIVE STUDY ON PARTICLE–FLUID INTERACTIONS IN MICRO AND NANOFLUIDS OF ALUMINIUM OXIDE; J. Hemalatha , T. Prabhakaran, R. Pratibha Nalini; Microfluid Nanofluid (2011) 10:263–270
 ON THE THERMAL PROPERTIES OF ASPARTIC ACID USING ULTRASONIC TECHNIQUE; M. Mohammed Nagoor Meeran, R. Raj Mohammed, P.Indra Devi,M.Sivabharathy and A. AbbasManthri; International Journal of ChemTech Research, CODEN (USA): IJCRGG ISSN : 09744290,Vol.6, No.7, pp 36853689, SeptOct 2014
 A PHOTOACOUSTIC AND ULTRASONIC STUDY ON JATROPHA OIL; G. Krishna Bama and K. Ramachandran; Journal of Engineering Physics and Thermophysics, Vol. 83, No. 1, 2010
 ULTRASONIC PROPERTIES OF NANOPARTICLESLIQUID SUSPENSIONS, R.R. Yadav, Giridhar Mishra, P.K. Yadawa, S.K. Kor, A.K. Gupta, Baldev Raj, T. Jayakumar, Ultrasonics, 48(2008) 591593
 THERMAL CONDUCTIVITY & SCATTERED INTENSITY OF ALUMINA (ALPHA) NANO PARTICLES IN ORGANIC BASE SOLVENT ; Dr. N. R. Pawar, Department of Physics, Arts, Commerce & Science College, Maregaon (M.S.); Presentation in NSA2015 (GOA)
Other properties possible with this Apparatus
 Adiabatic Compressibility
 Acoustic Impedance
 Characterization of Nanofluids/Suspensions
 Characterization of Ferro/Magnetic Nanofluids
 Intermolecular Free Length
Examples:
Ref: A. Varada Rajulu and P. Mabu Sab, Bull. Mater. Sci., Vol. 18 (June 1995), No. 3, pp. 247253.
Ref: P.S. Nikam and Mehdi Hasan, Asian Journal of Chemistry, Vol. 5 (1993), No. 2, pp. 319321.
