The freezing characteristics of small diameter eicosane (Tmelt = 37°C) droplets are studied here for their use in novel dry-cooling strategies based on spray freezing of recirculating phase change materials (PCM). PCM can be used to store thermal energy with relatively small changes in temperature (due to latent heat), as well as volume (due to small density changes). 4.2 mm diameter eicosane droplets are superheated to 40°C, placed on a cold stage at 10°C, and imaged during freezing (a). Similarly, liquid eicosane is enclosed within a custom-built experimental package creating a 5 mm diameter, 100 μm thick disc geometry with a temperature controlled boundary that is rapidly dropped from 40°C to 10°C (b). In both cases the liquid-solid interface is tracked, as well as the formation and growth of long dendrite structures which have been observed to play a critical role in the freezing process. (c) and (d) show the vertical position normalized by the droplet height , y/H, and the radial position (measured inward) normalized by the disc radius, r/R, of both the interface location and the average dendrite tip location. The total freezing time is observed visually, resulting in characteristic Fourier numbers of Fo = 0.55 ± 0.15 (droplet) and Fo = 3.5 ±0.15 (disc) at identical Stefan numbers of St = 0.3 ± 0.03, where the characteristic lengths are taken as the ratio of the eicosane volume to the cooled surface area.
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Dendrite Growth during Freezing of Millimeter-Scale Eicosane Droplets
Hamidreza Shabgard,
Hamidreza Shabgard
Department of Mechanical Engineering,
hamid.shabgard@gmail.com
Drexel University
, Philadelphia, PA
, USA
hamid.shabgard@gmail.com
Search for other works by this author on:
Philipp Boettcher,
Philipp Boettcher
Department of Mechanical Engineering,
philipp.boettcher@gmail.com
Drexel University
, Philadelphia, PA
, USA
philipp.boettcher@gmail.com
Search for other works by this author on:
Ying Sun
Ying Sun
Search for other works by this author on:
Md Mahamudur Rahman
Han Hu
Hamidreza Shabgard
Department of Mechanical Engineering,
hamid.shabgard@gmail.com
Drexel University
, Philadelphia, PA
, USA
hamid.shabgard@gmail.com
Philipp Boettcher
Department of Mechanical Engineering,
philipp.boettcher@gmail.com
Drexel University
, Philadelphia, PA
, USA
philipp.boettcher@gmail.com
Ying Sun
Corresponding author.
J. Heat Transfer. Aug 2015, 137(8): 080902
Published Online: August 1, 2015
Article history
Revised:
March 30, 2015
Received:
March 30, 2015
Online:
June 1, 2015
Citation
Rahman, M. M., Hu, H., Shabgard, H., Boettcher, P., and Sun, Y. (August 1, 2015). "Dendrite Growth during Freezing of Millimeter-Scale Eicosane Droplets." ASME. J. Heat Transfer. August 2015; 137(8): 080902. https://doi.org/10.1115/1.4030446
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