An Experimental Study on Flow and Heat Transfer Characteristics of Ethanol/Polyalphaolefin Nanoemulsion Flowing Through Circular Minichannels

JIAJUN XU

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Conference: 2017 ASEE Mid Atlantic Section Spring Conference
Location: Morgan State University, Baltimore, Maryland
Publication Date: April 7, 2017
Start Date: April 7, 2017
End Date: April 8, 2017
Page Count: 1
DOI: 10.18260/1-2--29248
Permanent URL: https://peer.asee.org/29248
Download Count: 579

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JIAJUN XU P.E. University of the District of Columbia

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Dr. Jiajun Xu, P.E. is an assistant professor of Mechanical Engineering Department at University of the District of Columbia. His research interests are Micro/Nanoscale materials for thermal Transport and Energy Conversion, Mechanical Design, Water Treatment techniques, and Multi-scale simulation. His research has been funded by National Science Foundation, U.S. Army Research office, Office of Naval Research, U.S. Department of Agriculture, and U.S. Geological Survey.

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Abstract

An Experimental Study on Flow and Heat Transfer Characteristics of Ethanol/Polyalphaolefin Nanoemulsion Flowing Through Circular Minichannels

Fana Zewede1, Henok Argaw 1, Jiajun Xu1 1 Department of Mechanical Engineering, University of the District of Columbia, DC 20008 USA

The need for advanced cooling technique has result many efforts to develop novel thermal management solutions including efficient heat exchangers, new heat transfer fluids and etc. Developing heat transfer fluids with improved thermal properties over those currently available is one of most challenging tasks in the heat transfer community. Therefore, more efforts must be made in this field to better understand how to enhance heat transfer using nanostructured materials and surface structures. Recently, a radically new design for thermal fluids, “nanoemulsion fluids” that completely eliminates solid particles, and instead, uses liquid nanostructures has been proposed. The nanoemulsion fluid can be formed spontaneously by self-assembly without need of external shear-induced rupturing. The phase changeable nanodroplets inside the nanoemulsion fluids have been experimentally discovered that their nucleation can enhance the heat transfer coefficient dramatically. However, it is urgently needed to characterize and understand the how the liquid nanostructure affects the convective flow and heat transfer properties.

This work experimentally studied the convective flow and heat transfer characteristics of a novel heat transfer fluid “Ethanol/Polyalphaolefin nanoemulsion” using 12 circular mini-channels of 1mm diameter. In this study, two nanoemulsion fluids with different concentrations of ethanol were used as working fluids and the effect of flow modes on the heat transfer is also investigated. The Reynolds number was varied from 100 to 5000 to cover the laminar to turbulent regions. Moreover, base fluid PAO flowing through the same mini-channels was tested as the baseline data. The experimental results show that: at same Reynolds number, the Nusselt number of Ethanol/PAO nanoemulsion is higher than that base fluid PAO. There is an increase of the pressure drop and earlier induction of the laminar-turbulent transition for the Ethanol/PAO nanoemulsion compared to base fluid PAO. At transitional flow regime, an oscillation of surface temperature has been observed and it has been attributed to the temperature dependent viscosity and thermal conductivity. The difference of viscosity and thermal conductivity between the PAO and nanoemulsion will affect the thermal boundary layer and that might be the reason for the increase of Nusselt number in transitional region. Future research involves more data on the fully developed turbulent region and different heat inputs may help understand the convective heat transfer of nanoemulsion.

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XU, J. (2017, April), An Experimental Study on Flow and Heat Transfer Characteristics of Ethanol/Polyalphaolefin Nanoemulsion Flowing Through Circular Minichannels Paper presented at 2017 ASEE Mid Atlantic Section Spring Conference, Morgan State University, Baltimore, Maryland. 10.18260/1-2--29248

TY - CPAPER
AB - An Experimental Study on Flow and Heat Transfer Characteristics of Ethanol/Polyalphaolefin Nanoemulsion Flowing Through Circular Minichannels

Fana Zewede1, Henok Argaw 1, Jiajun Xu1
1 Department of Mechanical Engineering, University of the District of Columbia, DC 20008 USA

The need for advanced cooling technique has result many efforts to develop novel thermal management solutions including efficient heat exchangers, new heat transfer fluids and etc. Developing heat transfer fluids with improved thermal properties over those currently available is one of most challenging tasks in the heat transfer community. Therefore, more efforts must be made in this field to better understand how to enhance heat transfer using nanostructured materials and surface structures. Recently, a radically new design for thermal fluids, “nanoemulsion fluids” that completely eliminates solid particles, and instead, uses liquid nanostructures has been proposed. The nanoemulsion fluid can be formed spontaneously by self-assembly without need of external shear-induced rupturing. The phase changeable nanodroplets inside the nanoemulsion fluids have been experimentally discovered that their nucleation can enhance the heat transfer coefficient dramatically. However, it is urgently needed to characterize and understand the how the liquid nanostructure affects the convective flow and heat transfer properties.

This work experimentally studied the convective flow and heat transfer characteristics of a novel heat transfer fluid “Ethanol/Polyalphaolefin nanoemulsion” using 12 circular mini-channels of 1mm diameter. In this study, two nanoemulsion fluids with different concentrations of ethanol were used as working fluids and the effect of flow modes on the heat transfer is also investigated. The Reynolds number was varied from 100 to 5000 to cover the laminar to turbulent regions. Moreover, base fluid PAO flowing through the same mini-channels was tested as the baseline data. The experimental results show that: at same Reynolds number, the Nusselt number of Ethanol/PAO nanoemulsion is higher than that base fluid PAO. There is an increase of the pressure drop and earlier induction of the laminar-turbulent transition for the Ethanol/PAO nanoemulsion compared to base fluid PAO. At transitional flow regime, an oscillation of surface temperature has been observed and it has been attributed to the temperature dependent viscosity and thermal conductivity. The difference of viscosity and thermal conductivity between the PAO and nanoemulsion will affect the thermal boundary layer and that might be the reason for the increase of Nusselt number in transitional region. Future research involves more data on the fully developed turbulent region and different heat inputs may help understand the convective heat transfer of nanoemulsion.
AU - JIAJUN XU P.E.
CY - Morgan State University, Baltimore, Maryland
DA - 2017/04/07
PB - ASEE Conferences
TI - An Experimental Study on Flow and Heat Transfer Characteristics of Ethanol/Polyalphaolefin Nanoemulsion Flowing Through Circular Minichannels
UR - https://peer.asee.org/29248
DO - 10.18260/1-2--29248
ER -