0
RESEARCH PAPERS

Evaporation/Boiling in Thin Capillary Wicks (II)—Effects of Volumetric Porosity and Mesh Size

[+] Author and Article Information
Chen Li

 Rensselaer Polytechnic Institute, Department of Mechanical, Aerospace and Nuclear Engineering Troy, NY 12180lic4@rpi.edu

G. P. Peterson

 University of Colorado, Boulder, CO 80309Bud.Peterson@colorado.edu

J. Heat Transfer 128(12), 1320-1328 (Jan 11, 2006) (9 pages) doi:10.1115/1.2349508 History: Received August 28, 2005; Revised January 11, 2006

Presented here is the second of a two-part investigation, designed to systematically identify and investigate the parameters affecting the evaporation from and boiling within, thin capillary wicking structures with a range of volumetric porosities and mesh sizes. The experimental studies were investigated under steady-state conditions at atmospheric pressure. Part I of the investigation described the wicking fabrication process and experimental test facility, and focused on the effects of the capillary wick thickness (ASME J. Heat Transfer., 128, pp. 1312–1319). In Part II, we examine the effects of variations in the volumetric porosity and the mesh size. The experimental results presented here indicate that the critical heat flux (CHF) was strongly dependent on both the mesh size and the volumetric porosity; while the evaporation/boiling heat transfer coefficient was significantly affected by mesh size, but not strongly dependent on the volumetric porosity. The experimental results further illustrate that the menisci at the CHF are located in the corners, formed by the wire and the heated wall and between the wires in both the vertical and horizontal directions. The minimum value of these three menisci determined the maximum capillary pressure generated through the capillary wick. The experimental results and observations are systematically presented and analyzed, and the local bubble and liquid vapor interface dynamics are examined theoretically. Based on the relative relationship between the heat flux and superheat, classic nucleate boiling theory, and the visual observations of the phase-change phenomena, as well as by combining the results obtained here with those obtained in Part I of the investigation, the evaporation/boiling heat transfer regimes in these capillary wicking structures are identified and discussed.

Copyright © 2006 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

(a) Heat flux as a function of superheat [Twall−Tsat] as a function of mesh size; (b) heat transfer coefficient as a function of heat flux as a function of mesh size

Grahic Jump Location
Figure 2

CHF as a function of wire diameter or pore size of sintered isotropic copper mesh

Grahic Jump Location
Figure 3

Schematic of the meniscus between the wire and the wall (17)

Grahic Jump Location
Figure 4

(a) SEM image of the compact six layer sample; SEM images of sintered isotropic copper mesh with 1509m−1(145in.−1), 56μm(0.0022in.) wire diameter, and fabricated at sintering temperature of 1030 °C with gas mixture protection (75%N2 and 25%H2) for two hours

Grahic Jump Location
Figure 5

(a) Heat flux as a function of superheat [Twall−Tsat] as a function of volumetric porosity; (b) heat transfer coefficient as a function of heat flux as a function of volumetric porosity

Grahic Jump Location
Figure 6

Test data of CHF as a function of volumetric porosity of the sintered isotropic copper mesh

Grahic Jump Location
Figure 7

(a) Typical q″-Tsuper curve for evaporation/boiling processes from uniformly sintered copper mesh surfaces (b) Typical heff-q″ curve for evaporation/boiling process from uniformly sintered copper mesh surfaces

Grahic Jump Location
Figure 8

Onset point of nucleate boiling for evaporation/boiling processes from uniformly sintered copper mesh surfaces

Grahic Jump Location
Figure 9

Local evaporation/boiling processes from wire surfaces and the corners between the wire and the heated surface

Grahic Jump Location
Figure 10

Local bubble dynamics and evaporation in evaporation/boiling processes on the surface

Grahic Jump Location
Figure 11

Models of heat transfer and vapor formation in wicks (14)

Grahic Jump Location
Figure 12

Control volume of the liquid-vapor interface

Grahic Jump Location
Figure 13

Heat flux distribution along the flow direction of the heater

Grahic Jump Location
Figure 14

Liquid-vapor interface and heat transfer model in the capillary wick structure 1. distilled water; 2. copper wire; 3. liquid-vapor interface; 4. initial liquid-vapor interface position; 5. interface position curve at uniform heat flux; 6. interface position at actual heat flux; 7. vapor bubble; 8. first dry out point

Grahic Jump Location
Figure 15

(a) Capillary wick surface before applied heat flux; (b) capillary wick after dry out. Progressive dry out processes in a capillary wick during evaporation/boiling

Tables

Errata

Discussions

Related

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