155 research outputs found
Non-Intrusive Temperature Measurements Using Microscale Visualization Techniques
lPIV is a widely accepted tool for making measured. This method allows simultaneous non-intrusive temperature and velocity measurements in integrated accurate measurements in microscale flows. The particles cooling systems and lab-on-a-chip devices. that are used to seed the flow, due to their small size, undergo Brownian motion which adds a random noise component to the measurements. Brownian motion intro- duces an undesirable error in the velocity measurements, but also contains valuable temperature information. A PIV algorithm which detects both the location and broadening of the correlation peak can measure velocity as well as temperature simultaneously using the same set of images. The approach presented in this work eliminates the use of the calibration constant used in the literature (Hohreiter et al. in Meas Sci Technol 13(7):1072–1078, 2002), mak- ing the method system-independent, and reducing the uncertainty involved in the technique. The temperature in a stationary fluid was experimentally measured using this technique and compared to that obtained using the particle tracking thermometry method and a novel method, low image density PIV. The method of cross-correlation PIV was modified to measure the temperature of a moving fluid. A standard epi-fluorescence lPIV system was used for all the measurements. The experiments were conducted using spherical fluorescent polystyrene-latex particles suspended in water. Temperatures ranging from 20 to 80°C wer
Engineered Nanostructures for High Thermal Conductivity Substrates
In the DARPA Thermal Ground Plane (TGP)
program[1],we are developing a new thermal technology
that will enable a monumental thermal technological leap
to an entirely new class of electronics, particularly
electronics for use in high-tech military systems. The
proposed TGP is a planar, thermal expansion matched heat
spreader that is capable of moving heat from multiple
chips to a remote thermal sink. DARPA’s final goals
require the TGP to have an effective conductivity of
20,000 W/mK, operate at 20g, with minimal fluid loss of
less than 0.1%/year and in a large ultra-thin planar package
of 10cmx20cm, no thicker than 1mm. The proposed TGP
is based on a heat pipe architecture[2], whereby the
enhanced transport of heat is made possible by applying
nanoengineered surfaces to the evaporator, wick, and
condenser surfaces. Ultra-low thermal resistances are
engineered using superhydrophilic and superhydrophobic
nanostructures on the interior surfaces of the TGP
envelope. The final TGP design will be easily integrated
into existing printed circuit board manufacturing
technology. In this paper, we present the transport design,
fabrication and packaging techniques, and finally a novel
fluorescence imaging technique to visualize the capillary
flow in these nanostructured wicks.United States. Defense Advanced Research Projects Agency (SSC SD Contract No. N66001-08-C-2008
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