Investigation of flow distribution and effect of aspect ratio on critical heat flux in multiple parallel microchannel fl
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ORIGINAL
Investigation of flow distribution and effect of aspect ratio on critical heat flux in multiple parallel microchannel flow boiling Ayyaz Siddique 1 & Ketan Sakalkale 1 & Sandip K. Saha 1
&
Amit Agrawal 1
Received: 13 May 2020 / Accepted: 19 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this paper, an experimental study on the effect of the low aspect ratio of microchannel on the critical heat flux (CHF) during saturated flow boiling of water is presented. Multiple parallel silicon microchannels with different aspect ratios, hydraulic diameter, and number of channels in the range of 0.2–0.5, 154.0–184.8 μm, and 3–9 respectively are fabricated, and the experiments are performed in the range of mass fluxes 24.1–806.5 kg m−2 s−1. It is found that the CHF is caused by the wall dryout near the microchannel exit. The effect of microchannel aspect ratio with the same hydraulic diameter on the CHF is found to be insignificant. Twenty-five CHF data points are obtained for microchannel flow boiling of water and are compared with the CHF predictive methods reported in the literature. A new CHF correlation is proposed, which predicts the measured CHF with the mean absolute deviation of 12.1%, which is substantially better than available CHF predictive methods. The findings from this study provide guidelines for designing multiple parallel microchannel heat sinks in two-phase flow for the thermal management of electronic equipment, spacecraft, satellites, energy conversion devices, and biomedical engineering. Nomenclature 2 Ach Microchannel cross-sectional H charea, m AR Aspect ratio of channel ¼ W ch: Þ 2 Ap Microchannel heated area, m cp Specific heat, J kg−1 °C−1 Dh Microchannel hydraulic diameter, m f Fanning friction factor G Mass flux, kg m−2 s−1 h Enthalpy, J kg−1 hz Local heat transfer coefficient, W m−2 °C−1 hfg Latent heat, J kg−1 Hch Microchannel depth, m Hhs Heat sink thickness, m2 k Thermal conductivity, W m−1 °C−1 K(∞) Hagenbach factor L Microchannel length, m La Laplace number ¼ σρμl D2 h l M Number of data points ˙ m Mass flow rate, kg s−1 N Number of channels
* Sandip K. Saha [email protected] 1
Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
Nu ΔPch ΔPminor pch q˙ q,, q,,c Rech T uch W Wch Wfin WeD WeL xin z zboiling
Nusselt number Pressure drop across the microchannel, Pa Minor pressure loss, Pa Heated perimeter of the microchannel (2Hch + Wch), m Power, W Wall heat flux, W m−2 Critical heat flux, W m−2 ˙ 4m Microchannel Reynolds number ¼ NπμD h Temperature, °C Liquid velocity in the microchannel, m s−1 Heat sink width, m Microchannel width, m Microchannel separation, m Weber number based on channel hydraulic diame2 ter ¼ GσρDh l 2 Weber number based on channel length ¼ GσρL l h −h Liquid subcooling at microchannel inlet ¼ inhfg f Location downstream from microchannel inlet, m Location where boiling starts from microchannel inlet, m
Greek symbols α Aspect ratio μ Dynamic vis
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