Benz­yl(meth­yl)phosphinic acid

The title compound, C8H11O2P, is a phosphinic compound with a tetra­coordinate penta­valent P atom. The phosphinic function plays a predominant role in the cohesion of the crystal structure, both by forming chains along the b axis via strong inter­molecular O—H⋯O hydrogen bonds and by cross-linking these chains perpendicularly via weak inter­molecular C—H⋯O hydrogen bonds, generating a two-dimensional network parallel to (001)

Characterization of Carbon Nanotube-Enhanced water as a phase change material for thermal energy storage systems

The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government.Innovation in electronics and directed energy technologies is accelerating as the 21st century progresses. The requirement to process, store and interpolate information and signals faster and with compact electronic units has led to the engineering of high power electronics. As the power density of these electronic systems increases, the demand for cooling increases. Development of directed energy systems also requires the dissipation of large heat loads. If the heat generated by high power electronics and other high energy systems is not reduced or transferred efficiently and quickly, resultant premature equipment failure, individual component failure or the inability to operate the equipment will occur. Carbon nanotube enhanced fluids have shown increases in the thermal conductivity from 20% to 250% when compared to the base heat transfer fluid. This study focuses on the stability of static, water-based, carbon nanotube enhanced mixtures during thermal cycling (i.e., freezing and thawing) of the nanofluid using various types of carbon nanotubes, loading percentages and surfactants. Electrical resistance measurements were recorded over a series of phase changes in order to assess the stability of the nanofluid. Experimental results showed that static, carbon nanotube enhanced nanofluids are stable between three to five freeze and thaw cycles before the carbon nanotubes start to agglomerate and subside. This resulted in an increased electric conductivity, and validated the use of electrical resistance measurements as a viable means of assessing the stability of the nanofluid. However, ultrasonication of the nanofluids after the instability recovers the original electric conductivity of the nanofluid.http://archive.org/details/characterization109454360US Navy (USN) author

Characterization of carbon nanotube-enhanced water as a phase change material for thermal energy storage systems

Innovation in electronics and directed energy technologies is accelerating as the 21st century progresses. The requirement to process, store and interpolate information and signals faster and with compact electronic units has led to the engineering of high power electronics. As the power density of these electronic systems increases, the demand for cooling increases. Development of directed energy systems also requires the dissipation of large heat loads. If the heat generated by high power electronics and other high energy systems is not reduced or transferred efficiently and quickly, resultant pre-mature equipment failure, individual component failure or the inability to operate the equipment will occur. Carbon nanotube enhanced fluids have shown increases in the thermal conductivity from 20% to 250% when compared to the base heat transfer fluid. This study focuses on the stability of static, water-based, carbon nanotube enhanced mixtures during thermal cycling (i.e., freezing and thawing) of the nanofluid using various types of carbon nanotubes, loading percentages and surfactants. Electrical resistance measurements were recorded over a series of phase changes in order to assess the stability of the nanofluid. Experimental results showed that static, carbon nanotube enhanced nanofluids are stable between three to five freeze and thaw cycles before the carbon nanotubes start to agglomerate and subside. This resulted in an increased electric conductivity, and validated the use of electrical resistance measurements as a viable means of assessing the stability of the nanofluid. However, ultrasonication of the nanofluids after the instability recovers the original electric conductivity of the nanofluid.Approved for public release; distribution is unlimited

Characterizing the stability of carbon nanotube-enhanced water as a phase change material for thermal management systems

The article of record as published may be found at http://dx.doi.org/10.1115/1.4003507Carbon nanotube (CNT) suspensions have shown promise as a heat transfer nanofluid due to their relatively high thermal conductivity and ability to remain in stable suspension for long durations. To assess their potential as a phase change material for thermal management systems, the stability of such suspensions under repeated phase change cycles is investigated. Electrical resistance testing was used to monitor stability of the CNT network during freeze-thaw cycling. With distilled water as the base fluid, the effects of CNT size and type, CNT concentration, surfactant type and concentration, and processing parameters were investigated. Nanofluids tested included laboratory-prepared and commercially supplied samples. Experiments showed breakdown of the nanofluid in less than 12 phase change cycles for all samples tested. Ultrasonication after breakdown was shown to restore resistance values to prebreakdown levels. The results suggest the use of CNT-enhanced water as a phase change material presents a significant operational challenge due to instability of the CNT network during phase change cycling. Should the use of such nanofluids be warranted as a phase change material, electrical resistance testing along with repeated ultrasonication may be considered as a means to control and monitor stability of the nanoparticle suspension in service