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A Thin Film Thermocouple (TFT) surface micro-machined on a Pyrex wafer was used to study micro-scale features in nucleate boiling. This study is relevant for various aerospace applications such as spray cooling, energy conversion devices and materials processing. The K-Type TFT was ~50 microns wide and ~250nm thick. A high speed digital data acquisition system was used to record the surface temperature fluctuations during pool boiling of PF-5060. The surface temperature transients were obtained at different superheats and data acquisition sampling rates up to 1 kHz. The spectra of surface temperature transients were analyzed using Fast Fourier Transform (FFT).

In this study, a molten salt-based high temperature nanofluid is explored for solar thermal energy conversion applications. The efficacy of the nanofluid as a heat transfer fluid (HTF) in concentrating solar power systems is explored in this study. The molten salt can enable higher operating temperature resulting in enhancement of the overall system efficiency for power generation (using, for example, a Rankine cycle or Stirling cycle). However, the usage of the molten salt as the HTF is limited due to their low specific heat capacity values (compared with, for example, water or silicone oils). The low specific heat of molten salt can be enhanced by doping small amount of nanoparticles. Solvents doped with minute concentration of nanoparticles are termed as "Nanofluids." Nanofluids are considered as attractive coolants for thermal management applications due to their anomalously enhanced thermal properties (compared with the neat solvent).

The aim of this study is to explore the anomalous variation of thermo-physical properties of aqueous nanofluids. The specific heat of three water-based nanofluids containing silicon dioxide (SiO₂), titanium dioxide (TiO₂), and aluminum oxide (Al₂O₃) nanoparticles were measured using a differential scanning calorimeter (DSC). Measurements were performed over a temperature range of 30°C - 80°C which was chosen to be between melting point and boiling point of water. The experiments were implemented with different sizes of nanoparticles to investigate the effect of the size of nanoparticles on the specific heat of nanofluids. The specific heat of the nanofluids was plotted as a function of the diameter of nanoparticles and the mass concentration of nanoparticles. The results indicate that the specific heat of aqueous nanofluids decreases as the mass concentration of nanoparticles increases from 0.5% to 20%.

Poly Alpha Olefins (PAO) are extensively used as cooling fluid for thermal management in avionics cooling applications owing to their superior physical and chemical properties, such as greater fluidity at low temperature, lower volatility, a higher viscosity index, lower pour point, better oxidative and thermal stability as well as low toxicity. Solvents doped with minute concentration of nanoparticles are termed as “Nanofluid”. Anomalous enhancements in thermo-physical property values as well as in heat transfer performance of nanofluids have been reported using nanofluids (compared to that for the neat solvent). The thermal interfacial resistance between the nanoparticle and the solvent molecules (Kapitza Resistance) is the dominant factor controlling the efficacy of the nanofluids for cooling applications.

The thermal characteristic of nanofluid for flow in a micro-channel is reported in this study by using an array of temperature nano-sensors. In this study, K-Type Thermocouples (Chromel/Alumel) were fabricated by surface micromachining process on a silicon wafer to obtain the thin film thermocouple array (TFTA). The micro-channel with TFTA was mounted on a heater (calorimeter) for imposing a specified heat flux on the bottom surface of the micro-channel. De-ionized water (DIW) was used as the test fluid for recording the temperature profile on the wafer substrate at different flow rates and heat fluxes. Aqueous nanofluids containing alumina nanoparticles were then used to record the temperature profiles under similar heat flux and flow conditions. The temperature profile was measured with the TFTA in a linear array of 5 columns and 2 rows of sensors while the volume flow rate was varied from 5 μl/min, to 7 μl/min and to 9 μl/min.