Abstract
In this paper, double manifolds are theoretically investigated for the scale-out of two-phase incompressible flows in small channels. Statistical descriptors are proposed to characterise the maldistribution of the total flow rate and the ratio of the flow rates in the two-phase channels, based on the variances and covariance of the flow rates of the two fluids. A novel resistance network model is developed that relates the flowrates of the fluids in the two-phase channels to the hydraulic resistances of the manifold. The statistical descriptors and the resistance network model are then used to develop relationships between the maldistribution coefficients and the hydraulic resistances of the double manifold, the overall pressure drop and the pumping power requirements for different parallel channel numbers. Based on these, scaling laws are proposed that maintain a constant degree of maldistribution for a scale-up factor up to 102. Double manifolds designed using these scaling laws have a constant pressure drop as the number of channels increases, whilst the power requirements increase linearly. The power requirements are inversely proportional to the phase ratio maldistribution descriptor. Recommendations for the design of double manifolds for the scale-out of two-phase systems are proposed.
Highlights
Over the last few years there have been many studies on small-scale units aiming at the intensification of multiphase processes, includingchemical syntheses [1,2], absorptions [3], extractions [4,5], andcrystallisations [6]
The most common metrics of flow distribution used in single phase flow distributors are shown in Table 1, where Qj is the flow rate in the jth channel, Q is the mean flow rate, and N is the number of parallel channels
The results show that RB/RR has a stronger influence over phase ratio maldistribution descriptor (PRM) than RA/RB
Summary
Over the last few years there have been many studies on small-scale units aiming at the intensification of multiphase processes, including (bio)chemical syntheses [1,2], absorptions [3], extractions [4,5], and (nano)crystallisations [6]. The benefits of operating in small channels stem from the reduction in length scales which result in short diffusion distances, increased importance of interfacial forces over inertial, viscous, and gravitational ones, large interfacial area-to-volume ratio (beneficial for mass transfer), and large channel surface-to-volume ratio (beneficial for heat transfer) The transition of these novel and efficient devices from benchscale to the industrial application involves increasing the throughput, often by using many of the single small-scale units in parallel (scale-out or numbering-up). A1, A2 B1, B2 C eq i j k N1, N2 R T T,1ch distribution sections barrier sections collection section equivalent either phase or fluid A given channel in a section of the double manifold A given channel in a section of the double manifold number of channels in scale-up main section total total, for one channel [12,13,14,15,16,17] This type of two-phase flow distributor has inherent benefits, including simple arrangement, small footprint, modularity, and passive control. The methodology for designing double manifolds for two-phase incompressible flows is summarised
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