scholarly journals Thermographical study of geometry and phase change influence on PDMS Microchannel liquid cooling devices

2021 ◽  
Vol 2116 (1) ◽  
pp. 012050
Author(s):  
Pedro Pontes ◽  
Lourenço Martins ◽  
Iva Gonçalves ◽  
Ana S Moita ◽  
António LN Moreira
Keyword(s):  
High Speed ◽  
Single Phase ◽  
Phase Flow ◽  
Ir Thermography ◽  
Single Phase Flow ◽  
Liquid Cooling ◽  
Ir Camera ◽  
Pressure Losses ◽  
Cooling Devices ◽  
Pdms Microchannel

Abstract This work proposes a methodology in which high speed camera imaging is combined with infrared (IR) thermography to look at the effect of geometric parameters and boiling in the effectiveness of these coolers. PDMS microchannels were manufactured with 3 channel widths: 250, 500 and 750µm. HFE7100 was used as the refrigerant. Pressure losses were significant for the thinnest geometry as clogging and flow reversal were observed. The dissipated heat flux, as measured by the IR camera was higher in the largest channels, due to the PDMS poor conductivity. Results obtained with HFE7100 were then compared with those obtained with water at single-phase flow. For the same geometry, HFE 7100 resulted in a higher heat transfer coefficient than water.

On the unsteady behaviour of cavity flow over a two-dimensional wall-mounted fence

2019 ◽  
Vol 874 ◽  
pp. 483-525 ◽  
Author(s):  
Luka Barbaca ◽  
Bryce W. Pearce ◽  
Harish Ganesh ◽  
Steven L. Ceccio ◽  
Paul A. Brandner
Keyword(s):  
High Speed ◽  
Single Phase ◽  
Free Stream ◽  
Free Stream Velocity ◽  
Small Scale ◽  
Stream Velocity ◽  
Phase Flow ◽  
Two Dimensional ◽  
Single Phase Flow ◽  
Dynamic Surface

The topology and unsteady behaviour of ventilated and natural cavity flows over a two-dimensional (2-D) wall-mounted fence are investigated for fixed length cavities with varying free-stream velocity using high-speed and still imaging, X-ray densitometry and dynamic surface pressure measurement in two experimental facilities. Cavities in both ventilated and natural flows were found to have a re-entrant jet closure, but not to exhibit large-scale oscillations, yet the irregular small-scale shedding at the cavity closure. Small-scale cavity break-up was associated with a high-frequency broadband peak in the wall pressure spectra, found to be governed by the overlying turbulent boundary layer characteristics, similar to observations from single-phase flow over a forward-facing step. A low-frequency peak reflecting the oscillations in size of the re-entrant jet region, analogous to ‘flapping’ motion in single-phase flow, was found to be modulated by gravity effects (i.e. a Froude number dependence). Likewise, a significant change in cavity behaviour was observed as the flow underwent transition analogous to the transition from sub- to super-critical regime in open-channel flow. Differences in wake topology were examined using shadowgraphy and proper orthogonal decomposition, from which it was found that the size and number of shed structures increased with an increase in free-stream velocity for the ventilated case, while remaining nominally constant in naturally cavitating flow due to condensation of vaporous structures.

Critical review on wax deposition in single-phase flow

Fuel ◽  
2021 ◽  
Vol 293 ◽  
pp. 120358
Author(s):  
Charlie van der Geest ◽  
Aline Melchuna ◽  
Letícia Bizarre ◽  
Antonio C. Bannwart ◽  
Vanessa C.B. Guersoni
Keyword(s):  
Critical Review ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Wax Deposition
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