Jet impingement can be particularly effective for removing
high heat fluxes from local hotspots. Two-phase jet
impingement cooling combines the advantages of both
the nucleate boiling heat transfer with the single-phase
sensible cooling. This study investigates two-phase confined
jet impingement cooling of local, laser-generated hotspots
in a 100 nm thick Hafnium (Hf) thin film on glass. The
jet/nozzle diameter is ∼1.2 mm and the normal distance
between the nozzle outlet and the heated surface is ∼3.2
mm. The jet coolants studied are FC 72, Novec 7200, and
Ethanol with jet nozzle outlet Reynolds numbers ranging
from 250 to 5000. The hotspot area is ∼0.06 mm2 and the
applied hotspot-to-jet heat fluxes range from 20 W/cm2 to
350 W/cm2. This heat flux range facilitates studies of both
the single-phase and two-phase heat transport mechanisms
for heat fluxes up to critical heat flux (CHF). The temporal
evolution of the temperature distribution of the laser-heated
surface is measured using infrared (IR) thermometry. This
study focuses on the stagnation point heat transfer - i.e.,
the jet potential core is co-aligned with the hotspot center.
For ethanol, the CHF is ∼315 W/cm2 at Re ∼ 1338 with a
corresponding heat transfer coefficient of h ∼ 102 kW/m2·K.
For FC 72, the CHF is ∼94 W/cm2 at Re ∼ 5000 with a
corresponding h ∼ 56 kW/m2·K. And for Novec 7200, the
CHF is ∼108 W/cm2 at Re ∼ 4600 with a corresponding
h ∼ 50 kW/m2·K.
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Thermal Transport in Nanoparticle Packings Under Laser Irradiation
Abstract Nanoparticle heating due to laser irradiation is of great interest in electronic, aerospace, and biomedical applications. This paper presents a coupled electromagnetic-heat transfer model to predict the temperature distribution of multilayer copper nanoparticle packings on a glass substrate. It is shown that heat transfer within the nanoparticle packing is dominated by the interfacial thermal conductance between particles when the interfacial thermal conductance constant, GIC, is greater than 20 MW/m2K, but that for lower GIC values, thermal conduction through the air around the nanoparticles can also play a role in the overall heat transfer within the nanoparticle system. The coupled model is used to simulate heat transfer in a copper nanoparticle packing used in a typical microscale selective laser sintering (μ-SLS) process with an experimentally measured particle size distribution and layer thickness. The simulations predict that the nanoparticles will reach a temperature of 730 ± 3 K for a laser irradiation of 2.6 kW/cm2 and 1304 ± 23 K for a laser irradiation of 6 kW/cm2. These results are in good agreement with the experimentally observed laser-induced sintering and melting thresholds for copper nanoparticle packing on glass substrates.
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- Award ID(s):
- 1728313
- PAR ID:
- 10195419
- Date Published:
- Journal Name:
- Journal of Heat Transfer
- Volume:
- 142
- Issue:
- 3
- ISSN:
- 0022-1481
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4045731
