Q-rates

Fig ure 6-1. Energy balanoe in ohemioal reaotors, where G = mass flow-rate u = internal energy per unit mass P = pressure p = fluid density m = mass of fluid in the system Q = rate at whioh heat is transferred to the system and = rate at whioh work is done on the surroundings. 

Due to the freezing limitations, the bounds are even more stringent than those given by Eq. (10.13). At the lowest permissible q rating temperature of the gas (190 K), the vapor pressure of the MEK is about 2.3 Pa. According to Eq. (10.. ib), the lower bound on can be calculated as follows ... 

Initial mass of A .Initial mass of B Initial mass of P Initial mass of Q Rate constant reaction 1 Rate constant reaction 2 RESET GOTO 1... 

Q = rate of heat transfer per unit mass of catalyst hf = heat transfer coefficient per unit of external surface area Tb = temperature at the bulk of the fluid Ts = temperature at catalytic surface. 

A = area for heat transfer t = specific heat capacity of medium H = heat content of steam relative to initial medium temperature = mass flow rate of steam At = initial mass of medium q= rate of heat transfer t = time T = temperature = initial temperature of medium = temperature of heat source and U = overall heat transfer coefficient. 

If the number of basic overall equations, Q, is smaller than that of basic routes, P, it is expedient to use a stoichiometric basis of routes for a description of the reaction. In this case we need to know only Q rates along nonempty basic routes the remaining P — Q rates are not required (but this by no means implies that they equal zero). 

Q = rate of heat removed or added per unit length of the reactor. 

Under a perturbation PQ the response (Q) rate, for the simplest case of first-order relaxation kinetics, can be written as... 

Here A represents the cross-sectional area of the inlet and outlet, z their elevations, u the fluid s mean velocity and p its density, nip is the total mass within the control volume, q rate of heat input to the control volume per unit mass and wx shaft work output from the control volume per unit mass. Note this is the Engineers convention for shaft work. In the Chemists convention, positive shaft work is an input to the control volume, i.e. the direction of positive shaft work is opposite. 

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