Vapor mass flow rate

As mentioned previously, two-phase flow discharges for fire scenarios are possible but not likely. To size the relief for fire and a single-vapor phase, use the heat input determined from Equations 9-36 to 9-38, and determine the vapor mass flow rate through the relief by dividing the heat input by the heat of vaporization of the liquid. This assumes that all the heat input from the fire is used to vaporize the liquid. The relief area is then determined using Equations 9-3 to 9-12. 

The vapor mass flow rate is proportional to the heat release rate and can be calculated in a similar way, as explained in Section 9.4.2 ... 

The vapor mass flow rate can be converted to a volume flow rate by using the vapor density calculated (Equation 10.10), which calculates the vapor velocity in the equipment using the section of the vapor tube ... 

Calculate the maximum allowable vapor mass-flow rate Gv. Now, vL = GL/pL, and vv... 

The inlet vapor mass flow rate is given by... 

Similarly the outlet vapor mass flow rate using information from the table is determined as 17.3 kg/s. 

Vapor mass flow rate per unit area... 

The specific water vapor mass flow rate mw sutf) (kghn2 s) to the diying air can be calculated as follows ... 

Figure 13-9 Correlation of the load factor (Fr = uvJuvsf at a fixed ratio of liquid to vapor mass flow rates, uvs = velocity of vapor based on the superficial area, ft/s, uvsf = velocity of the vapor based on the superficial area at the flood point, ft/s.) [W. L. Bolles and J. R. Fair, Third International Distillation Symposium, London, April 1979, No. 213 of E.F.C. Sec. 3.3, p. 35, by courtesy Institute of Chemical Engineers (London).]...

Fr flood ratio, at a fixed ratio of liquid to vapor mass flow rates... 

During steady-state operation, the liquid mass flow rate m, must equal the vapor mass flow rate mv at every axial position, and while the liquid flow regime is always laminar, the vapor flow may be either laminar or turbulent. As a result, the vapor flow regime must be written as a function of the heat flux. Typically, this is done by evaluating the local axial Reynolds number in the vapor stream. It is also necessary to determine whether the flow should be treated as compressible or incompressible by evaluating the local Mach number. 

Consider now conditions at the top tray. Both the liquid entering the tray and the vapor leaving it contain 80 mol% ethanol. The temperature there is around 351.4 K (see Table 6.2). The average molecular weight of both streams is 40.5 kg/kmol. Therefore, the liquid mass flow rate is L = (27.53)(40.5)/3600 = 0.310 kg/s the vapor mass flow rate is V = (40.43)(40.5)/3600 = 0.455 kg/s. For the conditions at the top tray, the following data are available from Wankat (1988) ... 

The liquid mass flow rate with the concentration Xq is fed in to the first effect with the pressure p. The concentration increases due to the evaporation of the solvent. The hquid mass flow rate L with the concentration x, is throttled by means of a valve and assumes the pressure P2 The vapor mass flow rate G, = Zq leaving the first effect enters the heating element of the second effect and is condensed according to the progress of heat transfer. It is assumed that the entering liquid solution is imdercooled and that a certain increase of its enthalpy is necessary to start boiling at pressure. The heat flow rates Q and Qi based on the mass flow rates Zq and L, respectively, can be expressed by the following enthalpy differences ... 

In a flashing nozzle, it is likely that evaporation starts before the hquid reaches the nozzle exit. Depending on the amount of vapor, liquid and vapor characteristics, velocity, and pipe geometry different flow regimes may be observed in a pipe leading to a nozzle. The flow regime inside a pipe depends on the flow quality X, defined as the ratio of vapor mass flow rate, m, to the total mass flow rate m ... 

Figure 10.20 shows the time-dependent variation of the residual inventory of the pool, of its temperature and of the vaporization mass flow rate. In order to obtain these results Eqs. (10.51)-( 10.60) were solved numerically. 

Thus we obtain the vaporization mass flow rate (in kg/s) due to heat input from the ground as... 

Fig. 10.22 Variation with time of the pool radius, the vaporization mass flow rate the and temperature after the release of chlorine...

As the vapor flow rates change from tray to tray in a nonequimolal overflow system, the tray with the highest vapor velocity will set the minimum column diameter. Knowing the vapor mass flow rate and the vapor density, the volumetric flow rate of the vapor can be calculated. Then, knowing the maximum allowable velocity, the cross-sectional area of the column can be calculated. 

The average vapor quality (/y) is obtained by the continuous averaging of the vapor quality along the minichannel. It can also be defined as the ratio between the average vapor mass flow rate and the total liquid flow injected (Eq. 16) ... 

Example 2.2.2 In the flash expansion desalination process (also called the flash vaporization process), cold sea water, heated to a temperature of 121 °C at the corresponding saturation pressure in a preheater, is allowed to enter a flash chamber where the temperature is 38 °C and the pressure is much lower at the corresponding saturation pressure. This produces some pure water vapor and a concentrated brine. In practical processes, the vapor mass flow rate produced can be at most 20% (Silver, 1966) of the feed brine mass flow rate. If the brine feed has 3.5 wt% salt, describe the separation achieved with the separation factors, extent of separation, distribution ratio and equilibrium ratio for two vapor flow rates expressed as a percentage of the feed brine mass flow rate (a) 20 wt%, (b) 10 wt%. 

The Baker plot as shown is only valid when the liquid and vapor mass flow rates per unit area are expressed in English units. For an inside diameter of 213.5 mm we have... 

Figure 8. Calculated SFa vapor mass flow rate and velocity vectors In the core and upper plenum for Test S-6. 

Water vapor mass flow rate includes water vapor present in both hydrogen and air outlet from the fuel cell, plus water generated by combustion of hydrogen in the burner ... 

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