Measurement of the thermal conductivity of nanofluids via transient hot wire method
Date Issued
2016
Date
2016
Author(s)
Chen, Chun-Chia
Abstract
Nanofluid is a liquid suspended stably with nanoparticles, whose sizes are from 1 – 100 nm. It was found in the literature that the thermal conductivity of nanofluid is substantially greater than that of the original liquid (called the base fluid), because of the introduction of nanoparticles. A common technique for accessing the thermal conductivity of nanofluid is the transient hot wire method. The goal of this thesis is to build up a transient hot wire device, and apply it to study the thermal conductivity gain of nanofluids under different situations. The transient hot wire device developed in this study was validated by comparing its measurements with several existing experimental data for wide ranges of experimental parameters。Furthermore, we found the followings which could be helpful for performing the experiments other than those stated in the literature. Low resistance resistors can be applied for the circuit of the Wheatstone bridge for avoiding the noise associated with high impedance output, long and thin platinum wire is helpful for calibrating the input voltage, and DAQ interface card for data acquisition can help to maintain the original signal undistorted. It is better to take the average of several data scanned before storage. For the thermal conductivity of nanofluids, we have performed measurements for different nanoparticles (TiO2, Al3O2, Fe3O4), base fluids (de-ionized water, ethylene glycol (EG), engine oil), and volume fractions for validation of the device. Based on the present measurements as well as the findings in the literature, we conclude: (1) the thermal conductivity of nanofluids increase with the volume fraction, irrespective of different nanoparticles and base fluids. The TiO2-water nanofluids perform better than TiO2-EG nanofluids, regarding the enhancement of thermal conductivity associated with the application of nanofluids. As the device is assembled in our laboratory, vary modification of the device can be easily implemented for different research. Electric wires were coiled around the test tube of the present-developed device, for accessing the magnetic effect on thermal conductivity of nanofluids. Preliminary experiments were performed using Fe3O4-Engine Oil nanofluids, and it was found that the thermal conductivity can indeed be increased via an applied magnetic field by passing electric current through the coil.
Subjects
Thermal conductivity
Transient hot wire method
Nanofluids
mean filter
DAQ acquisition card.
Type
thesis
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