Hydrodynamics and mass transfer of gas–liquid flow in a falling film microreactor

Abstract

In this article, flow pattern of liquid film and flooding phenomena of a falling film microreactor (FFMR) were investigated using high-speed CCD camera. Three flow regimes were identified as ''corner rivulet flow,'' ''falling film flow with dry patches,'' and ''complete falling film flow'' when liquid flow rate increased gradually. Besides liquid film flow in microchannels, a flooding presented as the flow of liquid along the side wall of gas chamber in FFMR was found at high liquid flow rate. Moreover, the flooding could be initiated at lower flow rate with the reduction of the depth of the gas chamber. CO 2 absorption was then investigated under the complete falling flow regime in FFMR, where the effects of liquid viscosity and surface tension on mass transfer were demonstrated. The experimental results indicate that k L is in the range of 5.83 to 13.4 Â 10 À5 m s À1 and an empirical correlation was proposed to predict k L in FFMR.

Flow pattern and break-up of liquid film in single-channel falling film microreactors

“…Flow patterns observed in the microchannel of SFFMRs were similar to those we have observed previously in multi-channel falling film microreactors [8]. They were identified as 'corner rivulet flow', 'falling film flow with dry patches' and 'complete falling film flow', as shown in Fig.…”

“…In a traditional large-sized falling film reactor, the flow pattern usually displays as finger flow, or falling film with dry patches [9]. But due to the micron-sized geometry, the flow pattern in falling film microreactors turns to be corner rivulet flow, falling film flow with dry patches, and complete falling film flow [8]. The complete falling film flow is the most favorable flow pattern for chemical reaction, which is only present when liquid flow rate is kept above a certain rate (defined as the minimum wetting flow rate, MWF).…”

“…To further improve the transfer rate and conversion of reactant in the liquid film, one possible way is to reduce the film thickness by decreasing the liquid flow rate. However, the complete falling film in the microchannel will breakup if the film thickness is sufficiently thin, which is obviously disadvantageous to the heat and mass transfer process [8]. To improve the reaction efficiency and optimize the operational condition, it is thus necessary to investigate liquid film break-up mechanism in microchannels.…”

Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

“…10,11 Many microscale devices such as micromixers and microreactors have been designed elaborately, and attracted increasing attention in both laboratories and commercial areas in recent years. [12][13][14][15][16][17][18] Highly efficient mixing performance is a general character of these devices, and most of them are designed to realize rapid mixing.…”

Investigation of heat transfer enhancement inside developing gravity-driven films along a vertical permeable plate subject to nonuniform suction

“…Appendix 1 Notation a 1 À a 6 correlation coefficients (C f , C f ) (local, average) skin friction coefficient (c p , k) fluid (specific heat, thermal conductivity (J kg 21 …”