0
Research Papers

Indirect Involvement of Amorphous Carbon Layer on Convective Heat Transfer Enhancement Using Carbon Nanofibers

[+] Author and Article Information
T. J. Taha

Thermal Engineering Laboratory,
Faculty of Engineering and Technology,
University of Twente,
P.O. Box 217,
Enschede 7500 AE, The Netherlands
e-mail: t.j.taha@utwente.nl; t_1915@yahoo.com

L. Lefferts

Catalytic Processes and Materials,
Faculty of Science and Technology,
University of Twente,
P.O. Box 217,
Enschede 7500 AE, The Netherlands

T. H. van der Meer

Thermal Engineering Laboratory,
Faculty of Engineering and Technology,
University of Twente,
P.O. Box 217,
Enschede 7500 AE, The Netherlands

1Corresponding author.

Manuscript received February 13, 2014; final manuscript received February 3, 2015; published online May 14, 2015. Assoc. Editor: L.Q. Wang.

J. Heat Transfer 137(9), 091007 (Sep 01, 2015) (8 pages) Paper No: HT-14-1075; doi: 10.1115/1.4030218 History: Received February 13, 2014; Revised February 03, 2015; Online May 14, 2015

In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nanostructures was achieved using catalytic chemical vapor deposition process on a 50 μm nickel wire at 650 °C. Due to their extremely high thermal conductivity, CNFs are used to augment/modify heat transfer surface. However, the inevitable layer of a-C that occurs during the synthesis of the CNFs layer exhibits low thermal conductivity which may result in insulating the surface. In contrast, the amorphous layer helps in supporting and mechanically stabilizing the CNFs layer attachment to the polycrystalline nickel (Ni270) substrate material. To better understand the influences of these two layers on heat transfer, the growth mechanism of the CNFs layer and the layer of carbon is investigated and growth model is proposed. The combined impact of both a-C and CNFs layers on heat transfer performance is studied on three different samples which were synthesized by varying the deposition period (16 min, 23 min, and 30 min). The microwire samples covered with CNF layers were subjected to a uniform flow from a nozzle. Heat transfer measurement was achieved by a controlled heat dissipation through the microwire to attain a constant temperature during the flow. This measurement technique is adopted from hot wire anemometry calibration method. Maximum heat transfer enhancement of 18% was achieved. This enhancement is mainly attributed to the surface roughness and surface area increase of the samples with moderate CNFs surface area coverage on the sample.

FIGURES IN THIS ARTICLE
<>
Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Heat transfer surface modification of wire mesh regenerator material. (a) Wire mesh regenerator material, (b) a differential strand of the wire mesh is used to investigate heat transfer performance, (c) CNFs layer synthesized [b → c] on the surface of the microwire using catalytic vapor deposition process, and (d) densely populated porous layer of CNFs.

Grahic Jump Location
Fig. 2

Schematic view of heat transfer measurement setup

Grahic Jump Location
Fig. 3

Bare nickel wire surface roughness morphology (a) before pretreatment and (b) after pretreatment

Grahic Jump Location
Fig. 4

SEM image illustration of carbon layer and CNFs layer on a Ni microwire. (a) CNF bundles rooted with a-C layer, (b) a-C layer with visible nickel nanoparticles, (c) visible surface cracks on a-C layer leading to CNFs growth, and (d) CNFs layer eruption from underneath the a-C layer.

Grahic Jump Location
Fig. 5

TEM images representative of CNFs grown at 650 °C on nickel microwire. (a) Closely grown CNFs with nickel particles at tip of the each individual fibers. (b) Individual CNF strongly anchored with a-C layer. (c) Rough fiber morphology of individual CNF created during the eruption of the fibers from underneath the a-C layer, and (d) CNF graphene layer arrangement.

Grahic Jump Location
Fig. 6

Schematic representation of proposed CNFs synthesis mechanism. (a) Nickel nanoparticles formed during surface pretreatment with H2, (b) initial carbon layer deposition on the nickel surface, (c) CNFs growth initiation creating eruption of the carbon layer due to the stress developed by the growth of CNFs, and (d) CNFs and carbon layer growth continue with time.

Grahic Jump Location
Fig. 7

3D surface measurement of CNFs layer at different growth time. (a) Bare nickel microwire surface, (b) CNF-16, (c) CNF-23, and (d) CNF-30.

Grahic Jump Location
Fig. 8

Average CNFs and a-C layers thickness at different synthesis time

Grahic Jump Location
Fig. 9

Influence of CNFs layer and a-C layer on: (a) convective heat transfer behavior and (b) heat transfer enhancement result obtained for sample produced at 650 °C for a duration of 16 min, 23 min, and 30

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In