Analysis of multidimensional models of monolith catalysts for hybrid combustors

Radiation heat transfer in catalytic monoliths

“…It is convenient to characterize these efforts in terms of their description of the gas phase within the catalytic passage, that is, whether the channel is one-dimensional (relying on heat-and mass-transfer coefficient correlations), two-dimensional (assuming axisymmetry, parallel flat plates, or external boundary-layer flow), or three-dimensional (no spatial simplifications). These studies have included: one-dimensional considerations of single passageways (Votruba et al, 1975;Heck et al, 1976;Young and Finlayson, 1976a,b;Sinkule and HlavLcek, 1978;Finlayson and Young, 1979;Marteney and Kesten, 1981;T'ien, 1981a,b;Oh and Cavendish, 1982;Prasad et al, 1983;Ahn et al, 1986;Zygourakis, 1989;Bennet et al, 1992;Tien and T'ien, 1992;Montreuil et al, 1992;Groppi et al, 1993;O h and Bissett, 1993;Leighton and Chang, 1995), multiple passageways (Flytzani-Stephanopoulos et al, 1986;Chen et al, 1988;Kolaczkowski et al, 1988;Kolaczkowski and Worth, 19951, two-dimensional solutions for single passageways (Heck et al, 1976;Young and Finlayson, 1976a,b;Finlayson and Young, 1979;Bennet et al, 1992;Lee and Aris, 1977;Harrison and Ernst, 1978;Zygourakis and Ark, 1983;Bruno et al, 1983;Ryan et al, 1991;Hayes et al, 1992Hayes et al, , 1996Boehman et al, 1992;Hayes and Kolaczkowsi, 1994;Groppi et al, 1995;Frye and Boehman, 1996;Boehman et al, 1997a,b), exter...…”

“…Most have included conduction heat transfer in the catalytic surface (monolith walls or flat plate), with the exception of Heck et al (19761, Mori et al (1977), T i e n (1981a,b), Schefer (1980), Brown et al (19831, Bruno et al (1983), Fakheri andBuckius (19841, Markatou et al (1991, 19931, andLeighton andChang (1995). Some have included radiation heat transfer, as well (Lee and h i s , 1977;Sinkule and Hlavhcek, 1978;Ryan et al, 1991;Bennet et al, 1992;Hayes et al, 1992Hayes et al, , 1996Boehman et al, 1992;Hayes and Kolaczkowski, 1994;Groppi et al, 1995;Kolaczkowski and Worth, 1995;Frye and Boehman, 1996;Boehman et al, 1997a,b). The level of detail in heterogeneous chemistry models has varied from generic global rate laws to global rate laws modified by effectiveness factors that account for pore diffusion in the catalytic layer (Young and Finlayson, 1976a,b: Hayes and Kolaczkowski, 19941, to solution of the governing equations for the surface diffusion of species in the catalytic layer (Zygourakis and Ark, 1983).…”

“…Recently, Groppi et al characterized the influences of developing flows, variable physical properties, conduction, and radiation on monolith catalytic combustor behavior (Groppi et al, 1995). In their simulations, Groppi et al relied on a correlation for radiation heat transfer that was originally developed by Lee and Aris (19771, which treats radiation as an "effective conductivity.…”

“…They considered the surfaces on the monolith combustor to be gray, but did not report the value of emissivity used in the calculations. Groppi et al (1995) simulated the catalytic combustion of CH, and considered a variety of parametric sensitivities, including hydrodynamic development, surface conductivity, radiation heat transfer, and homogeneous reactions. They concluded that for ceramic monolith combustors (as considered in the present work), conduction and radiation have a minimal effect on steady-state surface temperature distributions.…”

Geometry effects on ignition in catalytic monoliths

“…Many prior studies have dealt with the determination of heat and mass transfer coefficients in the presence of exothermic reaction in monolith channels of different geometric shapes (Benedetto et al, 2003;Groppi and Tronconi, 1997;Groppi et al, 1995aGroppi et al, , 1995bGroppi et al, , 2000Hayes and Kolaczkowski, 1994;Hayes et al, 1996;Tronconi and Forzatti, 1992;Young and Finlayson, 1976). Some of these studies focused on channels with a circular cross section, which are axisymmetric and thus do not have the corner effect (Benedetto et al, 2003;Hayes and Kolaczkowski, 1994;Hayes et al, 1996).…”