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f G k , = reaction rate constant in first-phase reaction (atm.-K p = thermodynamic equilibrium constant = PcH4*/'(PH,*)2 L = length of reactor, feet P, = total pressure. atm. P = partial pressure. atm. P* = equilibrium partial pressure, atm.C, = gas velocity, feet per sec. L't = terminal velocity of particles, feet per sec. I V = \veight of bed, lb.= fraction of carbon that reacts according to first-phase = gas feed rate, SCF per hour or moles per hour reaction hr.)-l efficients for first-phase reaction literature Cited (I) Dent. F. J., Gas. J . 244, 502 (1944). H U E B L E R , lliReaction kinetics and the mechanism of coal char hydrogasification in a pilot plant reactor under cocurrentand countercurrent-flow systems with both fluidized-and moving-bed contacting were studied. The rate of relatively slow second-phase reaction was investigated. Diffusional resistance was the major controlling factor at low gas velocities. Correlations for different controlling regimes are given, and the effect of major parameters on the rate of reaction is discussed. The good agreement between the correlated results and the experimental data indicates that the correlations and the proposed reaction model are satisfactory for design purposes. With previous study on the initial rapid reaction available, it i s now possible to predict the carbon conversion as well as the composition and heating value of the product gas a t the exit of the reactor under widely varying conditions.

We have measured the thermal conductivity of solid hydrogen in the temperature range of 1.4-13 K.Measurements were taken on a single sample over a 196-h period. During this time the ortho-hydrogen concentration changed from 75 to 19.8 at. %. Because precise temperature control allowed corrections to be made for chan~g ortho concentration, thermal conductivity versus temperature is given for constant orthohydrogen concentrations of 20, 30, 40, 50, 60, and 70 at. %. Addition of thermal resistances was assumed and-several curve fits to the data are given, including one with terms proportional to c ' T and cT '. An umklapp term is given that also agrees well with the data from previous experiments.

In recent years there has been a great focus of attention upon rapid heating methods employing radiation, convection, and induction. Concrete analyses of t h e effective value of convection versus radiation are difficult t o perform because of t h e inseparable character of t h e two phenomena. T h e present paper seeks t o compare, under theoretically ideal conditions, t h e effect of radiation and convection heating simultaneously applied t o a plate.For this purpose a n equivalent radiation "heat transfer coefficient" i s utilized, and although t h e differential equations involved are insoluble, graphical methods of solution are applied. T h e results reveal t h e contribution made by convection alone t o t h e total heat transfer attainable under assumed conditions and its ratio t o heat transfer by radiation.ECEKT denmistratioils oi iuiproved forging technique R and metal savings resuhing from est,reniely rapid heating have focused attention upon rapid heating methods. Extreniely rapid heating is practically scaleless; this gives lePs metal loss and provides the opport,unit,j for improved arid more accurate forgings.Although t,liere are a variety of possible methods fur accuniplishing rapid heating, such as induction heating. diffusion flames. radiation, and convection, practical considerations i n these e x t r e m temperature ranges place certain limitations upon the type of equipment that will be useful and economical.high. usuallj-above 2000" F., it has bcen more or l e s~ common practice to a s u m e that tlie contribution t80 the lientin:! rate of the work by convect,ive effects is neg1igil)ie cnmpared to r:rdiation. This rule of thumb has been coniniorily applicd as ail asioni i n furnace applicat,ion. Like all surh rules, after h11g use (.JiiC tends to forget the liniit,ai ions u1mi n-hich it v a s origiiiully liased and apply it to furnaces radically diffewnt from tlit, corivcntional types, and conaequrntly obtain performarices far diffewiit than expected. Recent esperiences i\-ith a new tl-pe uf furiiace (descrited belon-), specifically clr~~ipned for high conv as high temperature, indicat,e that this rule of thudJ i i entirel!. inadequate. It is the purpose of the present paper to demonstrate theoretically that under ideal conditions it niay 111; reasonable to expect t'he nierhanisrii of convectivt: licit ti,niihfer to reduce heating tinies approsiniately 20' untltw pur't: radiation, in contradiction to the coninionly used design procedure. The calculation, although carried out for a tteoretically ideal case: can definitely be used as an argunierit to design couvt:etive as well as radiative heat transfer rnechanisnis into furnaces operating even in these extreme ranges of industrial teniperaturee.To clarify the sit'uation further, the calculation has been carried far enough SO that, for the ideal case, it is possible to t,ell at a glance a t what temperatures the convective and radiative heat transfer rnechanisnis contribute equally to the over-all heat transfer. This can be used as a rough guide...