Crossflow monoliths

Fig. 43. Crossflow monolithic SOFC. From ref. [114]. This paper was originally presented at the Fall 1989 Meeting of The Electrochemical Society held in Hollywood, Florida.

Figure 11.47 Crossflow monolithic fuel cells with all unit cells connected in series (a) schematic showing external connections and (b) equivalent circuit (Michaels et al., 1986]...

In a separate set of four crossflow monoliths, a catalyst of similar composition (1.442% Cu emd 0.966% Cr) and density was coated exclusively on the walls of the reaction pass. No attempt was made to keep the catalyst from adhering to the section of wall adjacent to which no heat transfer medium flowed. 

Extension of the proposed cell model for one crossflow monolith to any number of crossflows is relatively straightforward. Each monolith is assigned an NXM grid while the triangular shaped chambers between the monoliths are treated as continuous stirred volumes. The stream entering each of the chambers has a temperature and composition that are the average of the streams leaving the crossflows. 

The authors would like to thank the Minnesota Mining and Manufacturing Company for supporting this investigation and supplying the ceramic crossflow monoliths. The Americcin Cyanamid Company supplied the catalyst. 

In the crossflow configuration widely used in the membrane separation industry today, the direction of the feed flow is perpendicular to that of the permeate flow. To increase the driving force for the permeate, a carrier stream to "sweep away the permeate is often used. In most of the membrane configurations such as tubes and multichannel monoliths described in Chapter 5, the carrier stream and the feed stream are generally co urrent or counter-current in direction. 

The configuration of the fuel cells is not limited to the tubular geometry. Michaels el al. [1986] fabricated monolithic fuel cells which basically have a crossflow configuration and all unit cells connected in scries (Figure 11.47) or in parallel (Figure 11.48) for the... 

Crossflow filtration membranes can be produced in flat sheet, hollow fiber, tubular formats when using polymeric materials, and in monolith and tubular configurations when using inorganic membrane materials. Table 14.2 summarizes the various module configurations. 

Figure 1.51 Examples of the membrane arrangements used in low shear crossflow membrane filters, (a) spiral wound (b) hollow fibre (c) plate and frame (d) tubular monolith (atech innovations).

The cell model ( ,2) is particularly well suited to describing the two dimensional temperature and concentration profiles in crossflow, including axial dispersion in these short passes (L/Dp<25 for the monoliths and catalyst used in this study). After neglecting the radial and interphase concentration and temperature gradients, we can write the modelling equations for a first order reaction with simultaneous... 

Experimental analyses of the heat transfer characteristics of the monolithic reactor-heat exchanger were carried out in the absence of reaction to define the NTU values in equations (1), (2), eind (3). Experiments were performed in which the coolcint pass flow rate was varied independently of the reaction pass flow rate, to produce j-factors vs Reynolds number, in good agreement with both the Graetz solution and data from an experimental study by Kays et al (] ) of a crossflow of similar design. 

The NTU values in equations (1) and (2) describing the heat loss from the monolithic reactor-heat exchanger chambers and crossflow shapes were evaluated using data obtained in stop flow experiments. Overall heat transfer coefficients based on the chamber wall area varied from 0.3 BTU/hr. ft °F to 0.55 BTU/hr. ft °F depending on the position in the reactor. 

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