Work

Slug flow boiling in microchannels at high vapour volume fraction

Year: 2025

Type: article

Abstract: In this work, we study experimentally the thermal performance and bubbly flow characteristics of convective boiling inside a multi-microchannel heat exchanger operated in slug flow regime at high vapour volume fraction (68%–85%). To that purpose, flow regime and heat transfer are characterised for a silicon/pyrex heat exchanger containing 16 parallel microchannels of hydraulic diameter 183 μ m with CO2 as the working fluid, for saturation temperatures close to − 35 ∘ C and heat fluxes range 12.7–69 kW / m 2 . The investigated boiling flow is characterised by a laminar regime, a high confinement, Capillary numbers O ( 1 0 − 2 ) and a Jakob number range of 0 . 1 ≤ J a ≤ 1 . The heat transfer is found to be monitored by the heat conduction in the liquid film forms between bubbles and the wall because of liquid adherence to the wall, very thin film thickness and large contact time with bubbles. Thus, experimental Nusselt numbers reveal to be close to the one predicted by the pure heat conduction problem in the liquid film. This study represents also the first measurement of heat transfer coefficients for CO2 boiling flow below − 30 ∘ C and for a hydraulic diameter below 200 μ m .

Source: International Journal of Heat and Mass Transfer

DOI: 10.1016/j.ijheatmasstransfer.2025.128115

Authors: M. Vacher, F. Ayela, R. Kossakowski, P. Delebecque, S. Jezequel, D. Colombet

Institutions: Centre National de la Recherche Scientifique, Laboratoire d’Annecy de Physique des Particules, Laboratoire des Écoulements Géophysiques et Industriels, Université Savoie Mont Blanc

Language: English

Topic: Heat Transfer and Boiling Studies

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,220

Funder: Institut National de Physique Nucléaire et de Physique des Particules