The temperature oscillation technique to measure the thermal diffusivity of a fluid consists of filling a cylindrical volume with the fluid, applying an oscillating temperature boundary condition at the two ends of the cylinder, measuring the amplitude and phase of the temperature oscillation at any point inside the cylinder, and finally calculating the fluid thermal diffusivity from the amplitude and phase values of the temperature oscillations at the ends and at the point inside the cylinder. Although this experimental technique was introduced by Santucci and co-workers nearly two decades ago, its application is still limited, perhaps because of the perceived difficulties in obtaining accurate results. Here, we attempt to clarify this approach by first estimating the maximum size of the liquid’s cylindrical volume, performing a systematic series of experiments to find the allowable amplitude and frequency of the imposed temperature oscillations, and then validating our experimental setup and the characterization method by measuring the thermal conductivity of pure water at different temperatures and comparing our results with previously published work.

VL - 49 UR - http://www.sciencedirect.com/science/article/pii/S001793100600144X IS - 17-18 ER - TY - JOUR T1 - Characterization of the Temperature Oscillation Technique to Measure the Thermal Conductivity of Fluids JF - International Journal of Heat and Mass Transfer Y1 - 2006 A1 - Prajesh Bhattacharya A1 - S. Nara A1 - P. Vijayan A1 - Tang, T. A1 - W. Lai A1 - Patrick E. Phelan A1 - Ravi S. Prasher A1 - David W. Song A1 - J. Wang KW - Temperature oscillation technique KW - Thermal conductivity KW - thermal diffusivity AB -The temperature oscillation technique to measure the thermal diffusivity of a fluid consists of filling a cylindrical volume with the fluid, applying an oscillating temperature boundary condition at the two ends of the cylinder, measuring the amplitude and phase of the temperature oscillation at any point inside the cylinder, and finally calculating the fluid thermal diffusivity from the amplitude and phase values of the temperature oscillations at the ends and at the point inside the cylinder. Although this experimental technique was introduced by Santucci and co-workers nearly two decades ago, its application is still limited, perhaps because of the perceived difficulties in obtaining accurate results. Here, we attempt to clarify this approach by first estimating the maximum size of the liquid’s cylindrical volume, performing a systematic series of experiments to find the allowable amplitude and frequency of the imposed temperature oscillations, and then validating our experimental setup and the characterization method by measuring the thermal conductivity of pure water at different temperatures and comparing our results with previously published work.

VL - 49 UR - http://www.sciencedirect.com/science/article/pii/S001793100600144X IS - 17-18 ER - TY - JOUR T1 - Effect of Aggregation Kinetics on the Thermal Conductivity of Nanoscale Colloidal Solutions (Nanofluids) JF - Nanoletters Y1 - 2006 A1 - Ravi S. Prasher A1 - Prajesh Bhattacharya A1 - Patrick E. Phelan VL - 6 ER - TY - CONF T1 - Effect of Coloidal Chemistry on the Thermal Conductivity of Nanofluids T2 - International Mechanical Engineering Congress & Exposition Y1 - 2006 A1 - Ravi S. Prasher A1 - Prajesh Bhattacharya A1 - Patrick E. Phelan JF - International Mechanical Engineering Congress & Exposition CY - Chicago, IL ER - TY - JOUR T1 - Enhanced Mass Transport in Nanofluids JF - Nanoletters Y1 - 2006 A1 - S. Krishnamurthy A1 - Prajesh Bhattacharya A1 - Patrick E. Phelan A1 - Ravi S. Prasher AB -Thermal conductivity enhancement in nanofluids, which are liquids containing suspended nanoparticles, has been attributed to localized convection arising from the nanoparticles' Brownian motion. Because convection and mass transfer are similar processes, the objective here is to visualize dye diffusion in nanofluids. It is observed that dye diffuses faster in nanofluids compared to that in water, with a peak enhancement at a nanoparticle volume fraction, *φ*, of 0.5%. A possible change in the slope of thermal conductivity enhancement at that same *φ* signifies that convection becomes less important at higher *φ*. The enhanced mass transfer in nanofluids can be utilized to improve diffusion in microfluidic devices.

The heat transfer abilities of fluids can be improved by adding small particles of sizes of the order of nanometers. Recently a lot of research has been done in evaluating the thermal conductivity of nanofluids using various nanoparticles. In our present work we address this issue by conducting a series of experiments to determine the effective thermal conductivity of alumina-nanofluids by varying the base fluid with water and antifreeze liquids like ethylene glycol and propylene glycol. Temperature oscillation method is used to find the thermal conductivity of the nanofluid. The results show the thermal conductivity enhancement of nanofluids depends on viscosity of the base fluid. Finally the results are validated with a recently proposed theoretical model.

JF - ASME International Mechanical Engineering Congress and Exposition, November 5-11, 2005 PB - ASME CY - Orlando, FL SN - 0-7918-4221-5 ER - TY - JOUR T1 - Thermal Conductivity of Nanoscale Colloidal Solutions (Nanofluids) JF - Physical Review Letters Y1 - 2005 A1 - Ravi S. Prasher A1 - Prajesh Bhattacharya A1 - Patrick E. Phelan VL - 94 IS - 025901-1 – 025901-4. ER - TY - JOUR T1 - Brownian Dynamics Simulation to Determine the Effective Thermal Conductivity of Nanofluids JF - Journal of Applied Physics Y1 - 2004 A1 - Prajesh Bhattacharya A1 - Saha, S.K. A1 - Ajay K. Yadav A1 - Patrick E. Phelan A1 - Ravi S. Prasher KW - complex fluids KW - Disperse systems KW - Thermal conduction in nonmetallic liquids AB -A nanofluid is a fluid containing suspended solid particles, with sizes on the order of nanometers. Normally, nanofluids have higher thermal conductivities than their base fluids. Therefore, it is of interest to predict the effective thermal conductivity of such a nanofluid under different conditions, especially since only limited experimental data are available. We have developed a technique to compute the effective thermal conductivity of a nanofluid using Brownian dynamics simulation, which has the advantage of being computationally less expensive than molecular dynamics, and have coupled that with the equilibrium Green-Kubo method. By comparing the results of our calculation with the available experimental data, we show that our technique predicts the thermal conductivity of nanofluids to a good level of accuracy.

VL - 95 IS - 11 ER - TY - CONF T1 - Determining the Effective Viscosity of a Nanofluid Using Brownian Dynamics Simulation T2 - 1st International Symposium on Micro & Nano Technology Y1 - 2004 A1 - Prajesh Bhattacharya A1 - Patrick E. Phelan A1 - Ravi S. Prasher JF - 1st International Symposium on Micro & Nano Technology CY - Honolulu, HI ER - TY - CONF T1 - Evaluation of the Temperature Oscillation Technique to Calculate Thermal Conductivity of Water and Systematic Measurement of the Thermal Conductivity of Aluminum Oxide – Water Nanofluiids T2 - International Mechanical Engineering Congress & Exposition, Y1 - 2004 A1 - Prajesh Bhattacharya A1 - P. Vijayan A1 - Tang, T. A1 - S. Nara A1 - Patrick E. Phelan A1 - Ravi S. Prasher A1 - J. Wang A1 - David W. Song JF - International Mechanical Engineering Congress & Exposition, CY - Anaheim, CA ER - TY - CONF T1 - Determining the Effective Thermal Conductivity of a Nanofluid Using Brownian Dynamics Simulation T2 - National Heat Transfer Conference Y1 - 2003 A1 - Prajesh Bhattacharya A1 - Saha, S.K. A1 - Ajay K. Yadav A1 - Patrick E. Phelan A1 - Ravi S. Prasher JF - National Heat Transfer Conference CY - Las Vegas, NV ER - TY - JOUR T1 - Nanofluids for Heat Transfer Applications JF - Annual Review of Heat Transfer Y1 - 1995 A1 - Patrick E. Phelan A1 - Ravi S. Prasher A1 - Prajesh Bhattacharya VL - 14 ER -