Heat and Fluid Flow In an Integrated Rectangular Microchannel: A Combined Numerical-Experimental Study
Date
2022
Authors
G., Narendran
Journal Title
Journal ISSN
Volume Title
Publisher
National Institute of Technology Karnataka, Surathkal
Abstract
This thesis work presents numerical and experimental investigations on flow maldistribution
based conjugate axial conduction problems in parallel type channels for high density
electronic cooling applications. Majorly, three issues relating to the practicality of the
integrated parallel channel heat sinks are explored in the thesis: (a) The effect of integrated
heat spreaders in mitigating the flow induced high temperature zones using parallel type heat
sink, (b) The study of axial conduction and entrance effects of heterogeneous integrated heat
sink and (c) the use of inertial channels to reduce flow maldistribution induced axial
conduction in parallel flow type configuration heat sink.
In the first part, heat transfer investigations are performed to reduce hotspots with heat
spreader integrated microchannel using nanofluid. The results of Nusselt number are
compared with the benchmark literatures. Numerical simulations on microchannel heat sink
are performed to understand the temperature distribution in the spreader and an elaborate
discussion is provided for the deviations observed between numerical and experimental data.
Critical effects like response time and bulk diffusion are discussed by varying hotspot, aspect
ratio and processor cores. Reduction in flow induced hotspot has been observed by providing
graphene oxide nanofluid with very low volume fraction. In the second part, both the
numerical and experimental analyses are performed to investigate axial conduction in
heterogeneous integrated microchannel using TiO2 nanofluid. The inlet flow rate, volume
fraction and power rating are varied to check the effects of axial conduction on
heterogeneously integrated substrates. The thermo physical properties of the TiO2 nanofluid
are measured and characterized. Significant effect of axial conduction is seen for nanofluid
at higher concentration at reduced flow rates. On the other hand, it has been observed that
the effect of conjugate heat transfer decreases at higher flow rates.
The last part of the work presents the investigation on the special type of inertial channels to
reduce the maldistribution induced axial conduction. The study is carried out on ribbed
channels with three different geometrical configurations i.e. normal, inclined and lifted
channels. The average temperature of the sink reduces for ribbed channels than normal
straight channels. The effect of axial conduction is observed less for ribbed inclined channel
due to the obstruction in flow, flow separation and increased fluid momentum in extreme
channels.
Description
Keywords
microchannel, nanofluid, axial conduction, maldistribution