Header design for flow equalization in microstructured reactors

Abstract

in Wiley InterScience (www.interscience.wiley.com).To enhance the uniformity of fluid flow distribution in microreactors, a header configuration consisting of a cone diffuser connected to a thick-walled screen has been proposed. The thick-walled screen consists of two sections: the upstream section constitutes a set of elongated parallel upstream channels and the downstream section constitutes a set of elongated parallel downstream channels positioned at an angle of 908 with respect to the upstream channels. In this approach the problem of flow equalization reduces to that of flow equalization in the first and second downstream channels of the thick-walled screen. In turn, this requires flow equalization in the corresponding cross sections of the upstream channels. The computational fluid dynamics analysis of the fluid flow maldistribution shows that eight parallel upstream channels with a width of 300-600 mm are required per 1 cm of length for flow equalization. The length to width ratio of these channels has to be >15. The numerical results suggest that the proposed header configuration can effectively improve the performance of the downstream microstructured devices, decreasing the ratio of the maximum flow velocity to the mean flow velocity from 2 to 1.005 for a wide range of Reynolds numbers (0.5-10).

Design of a thick-walled screen for flow equalization in microstructured reactors

“…As parameter a increases, the b/a ratio has to be reduced to obtain flow equalization in the whole range of values of parameter a [6,14]. Therefore, the problem can be formulated as finding an optimum fit, which minimizes the flow nonuniformity index defined as…”

“…In this work, the CFD code FLUENT R 6.0 was used to simulate the fluid flow distribution and pressure drops along the screens. The governing equations were the same as applied in [6]. The semi-implicit SIMPLER algorithm is used in the velocity and pressure conjugated problem.…”

“…A CFD analysis was performed on this type of header [14]. The geometry of the inlet section allows us to obtain a highly uniform distribution of fluid flow at the end face of the inlet section (or to the inlet face of a downstream reactor), regardless of the fluid flow distribution profile at the inlet face of the upstream channels [6]. The approach for flow equalization in a downstream microreactor was presented by the application of a thick-wall screen, in which parameter b was adjusted in a way that function f, given by equation (1), has to be equal to unity [6]:…”

“…In turn, this requires flow equalization in the corresponding cross-sections of the upstream channels (figure 2(a)), which have been modeled by rectangular and parallel plate geometries. In this way, the hydraulic conductance and the corresponding Po numbers were calculated for a rectangle with height z V 1 obtained by the topmost and bottommost portion of upstream channels merged together (figure 2(b)), and for the middle part which was considered as parallel plates with height z V 2 (figure 2(c)) [6]. The results of the CFD simulations were verified by measuring flow distribution at the outlets of the downstream channels by Laser Doppler Anemometry (LDA) as described elsewhere [16].…”

“…Recently, we proposed a header consisting of a flow diffuser and a thick-walled screen consisting of upstream and downstream parallel channels for flow equalization over the cross-section of a microstructured reactor [6,13]. The upstream section (U) comprises a set of m elongated parallel upstream channels, and the downstream section (D) comprises a set of n elongated parallel downstream channels positioned at an angle of 90…”