Mixing energy balance

Material and energy balances are based on the conservation law, Eq. (7-69). In the operation of liquid phase reactions at steady state, the input and output flow rates are constant so the holdup is fixed. The usual control of the discharge is on the liquid level in the tank. When the mixing is adequate, concentration and temperature are uniform, and the effluent has these same properties. The steady state material balance on a reacdant A is... 

Mass and Energy Balances Due to the good mixing and heat-transfer properties of fluidized beds, the exit-gas temperature is assumed to be the same as the bed temperature. Fluidized bed gran-... 

Mixing of two air flows. As illustrated in Fig 4.15i3, the energy balance is... 

The room models implemented in the codes can be distinguished further by how detailed the models of the energy exchange processes are. Simple models use a combined convective-radiative heat exchange. More complex models use separate paths for these effects. Mixed forms also exist. The different models can also be distinguished by how the problem is solved. The energy balance for the zone is calculated in each time step of the simulation. 

The mass, momentum and energy balances for the mixing zone are... 

Setting f = Tout, H = Hout, and so on, specializes the integral energy balance of Equation (5.14) to a perfectly mixed, continuous-flow stirred tank ... 

FIGURE 35.11 Typical energy balance of one batch-mixing process on a GK320E mixer (styrene-butadiene rubber/carbon black [SBR/CB] compound). 

The mass and energy balance equations for ideally mixed components where zero-order reaction proceeds are ... 

Energy balance around mixing tee, taking as the datum temperature the inlet temperature to the oxidiser, f3. 

In principle, if the temperatures, velocities, flow patterns, and local rates of mixing of every element of fluid in a reactor were known, and if the differential material and energy balances could be integrated over the reactor volume, one could obtain an exact solution for the composition of the effluent stream and thus the degree of conversion that takes place in the reactor. However, most of this information is lacking for the reactors used in laboratory or commercial practice. Consequently, it has been necessary to develop approximate methods for treating... 

The temperature at the inlet to stage i, Toi, may similarly be related to Ti l, the temperature at the outlet of the previous stage, by means of an energy balance around Mj-i- If we assume cP is constant for the relatively small temperature changes involved on mixing (and ignore any compositional effect), an enthalpy balance around Mj is... 

As our next fairly simple system let us consider a process in which two energy balances are needed to model the system. The flow rate f of oil passing through two perfectly mixed tanks in series is constant at 90 ft min. The density p of the oil is constant at 40 and its heat capacity Cp is 0.6 Btu/lb °F. The volume... 

For exothermic reactions in mixed flow (or close to mixed flow) an interesting situation may develop in that more than one reactor composition may satisfy the governing material and energy balance equations. This means that we may not know which conversion level to expect, van Heerden (1953, 1958) was the first to treat this problem. Let us examine it. 

A reactor will be isothermal at the feed inlet temperature Tq if (1) reactions do not generate or absorb significant heat or (2) the reactor is thermostatted by contact with a temperature bath at coolant temperature Tq. For any other situation we will have to solve the energy-balance equation long with the mass balance to find the temperature in the reactor. We therefore must set up these equations for our mixed and unmixed reactors. 

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