Temperature adiabatic mixing

The recycle rate is 200.6 mol/s, and the adiabatic mixing temperature is 64.5°C. Any of the input variable values could now be changed and the flowchart easily recalculated. 

To calculate the adiabatic mixing temperature dp the pressure dependence of the specific enthalpy is neglected. Then setting... 

The adiabatic mixing temperature from (1.30) is the link between the local heat transfer coefficient a from (1.23) and the enthalpy flow for every cross section, because from (1.26), (1.27) and (1.31) follows... 

The adiabatic mixing temperature dp is different from the integrated average of the cross sectional temperature... 

In tubular flow, M = gwmR2ir, dAq = 2rn dr and therefore the adiabatic mixing temperature, under the assumption g = const, is... 

This says that the temperature increase at the wall in a thermal fully developed flow changes with the length x in the same way as the difference between the wall and the adiabatic mixing temperature. The temperature profile that satisfies this condition is of the general form... 

Fig. 3.33 Dependence of the wall temperature tfo i) and adiabatic mixing temperature on the length x in...

The adiabatic mixing temperature (3.226) is found by inserting the temperature profile into... 

The local Nusselt number is obtained from the adiabatic mixing temperature with the help of the energy balance... 

For sufficiently large values of the length X+ —> oo the adiabatic mixing temperature (3.249) may be calculated using only the first term of the series. The mean Nusselt number according to (3.251) is then transformed into... 

For X+ oo, the known end value of 3.6568 for the Nusselt number for thermal fully developed flow is obtained. The calculation of the Nusselt number for small values of the length X+ = L/(dPe) requires many terms of the series for the adiabatic mixing temperature (3.249). Therefore the exact solution has been approximated by empirical equations. According to Stephan [3.30] through... 

All the material properties are taken at the adiabatic mixing temperature. With large differences in the temperature of the fluid and the wall, the influence of the viscosity that changes markedly with the temperature has to be taken into consideration. Hufschmidt and Burck [3.35] found, based on experiments by Sieder and Tate [3.36], that it is sufficient to multiply the right hand side of (3.262) with the factor... 

Here aB is the heat transfer coefficient for nucleate boiling from section 4.2.6, ac is that by forced, single phase flow, sections 3.7.4, page 338, and 3.9.3, page 384, L is the adiabatic mixing temperature of the liquid. 

The temperature achieved when two fluid streams of differing temperature and/or composition are adiabat-ically mixed is termed the adiabatic mixing temperature. Compute the adiabatic mixing temperature for the following two cases ... 

Explain why the adiabatic mixing temperature is greater than that of either of the initial solutions in one of these cases, and intermediate between those of the initial solutions in the other case., ... 

Adiabatic-Saturation Temperature, or Constant-Enthalpy Lines If a stream of air is intimately mixed with a quantity of water at a temperature t, in an adiabatic system, the temperature of the air will drop and its humidity will increase. If t, is such that the air leaving the system is in equihbrium with the water, t, will be the adiabatic-saturation temperature, and the line relating the temperature and humidity of the air is the adiabatic-saturation line. The equation for the adiabatic-saturation line is... 

A plot of (m/VP2 )(TR —T0) versus TR reveals a multivalued graph that exhibits a maximum as shown in Fig. 4.51. The part of the curve in Fig. 4.51 that approaches the value Tx asymptotically cannot exist physically since the mixture could not be ignited at temperatures this low. In fact, the major part of the curve, which is to the left of Topt, has no physical meaning. At fixed volume and pressure it is not possible for both the mass flow rate and temperature of the reactor to rise. The only stable region exists between Topt to T. Since it is not possible to mix some unbumed gases with the product mixture and still obtain the adiabatic flame temperature, the reactor parameter must go to zero when TR = T. ... 

NjO, NOj, HONO, and HNO3, with a total heat release of approximately 240 kj moh. P These molecules react in the gas phase to form O2, H2O, and N2 as the final combustion products and the adiabatic flame temperature reaches 3640 K. The excess oxygen molecules act as an oxidizer when ADN is mixed with fuel components. 

Table 9.3 shows the measured detonation velocities and densities of various types of energetic explosive materials based on the data in Refs. [9-11]. The detonation velocity at the CJ point is computed by means of Eq. (9.7). The detonation velocity increases with increasing density, as does the heat of explosion. Ammonium ni-trate(AN) is an oxidizer-rich material and its adiabatic flame temperature is low compared with that of other materials. Thus, the detonation velocity is low and hence the detonation pressure at the CJ point is low compared with that of other energetic materials. However, when AN particles are mixed with a fuel component, the detonation velocity increases. On the other hand, when HMX or RDX is mixed with a fuel component, the detonation velocity decreases because HMX and RDX are stoichiometrically balanced materials and the incorporation of fuel components decreases their adiabatic flame temperatures. 

The adiabatic flame temperature, is 2220 K at (0.0), i. e., without B or A1 particles. Tf remains relatively unchanged in the region of less than 0.05, but then rises to a maximum of 2260 K at b(0. 15). On the other hand, when A1 is mixed with AP, Tjreaches a maximum of 3000 K at The maximum flame temperature... 

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