Transfer units and

Hq and aie called the overall gas-phase height of a transfer unit and the number of overall gas-phase transfer units, respectively. In the case of a straight equiUbrium line, is often neady concentration-independent as explained earher. In such cases, use of equation 47 is especially convenient... 

The following tabulation of calculations shows the relationship between the number of transfer units and the percent of solute removed from the gas stream ... 

Hughmark [181] has proposed empirical correlations for better fit of experimental data to transfer units and thus tray efficiency comparison with the AIChE method [2]. 

Determine the number of transfer units, and the packed tower height. 

This problem steps off six full transfer units and approximately K of the seventh. Report as 6.33 units. 

Table 1.5 Dependence of the number of micro channels N, their length L, the cross-sectional area of the reactor S and the pressure drop AP on the micro-channel diameter, when the efficiency (i.e. a fixed number of transfer units) and at least one specific characteristic quantity are kept fixed in each line. Three cases with operation time-scales varying as (c/m)°. are considered [114],...

For a packed column the chart by Colburn (1939) can be used (see Volume 2, Chapter 11). This gives the ratio of the inlet and outlet concentrations, yi/yt, in terms of the number of transfer units and niGm/Lm. 

The methods for estimating the heights of transfer units, HTU, given in Section 11.14.3 can be used for distillation. The relationship between transfer units and the height of an equivalent theoretical plate, HETP is given by ... 

For design purposes it is convenient to write equations 11.97 and 11.98 in terms of transfer units (HTU) where the value of integral is the number of transfer units, and the group in front of the integral sign, which has units of length, is the height of a transfer unit. 

The relationship between the overall height of a transfer unit and the individual film transfer units H, and HG, which are based on the concentration driving force across the liquid and gas films, is given by ... 

Many correlations have been published for predicting the height of a transfer unit, and the mass-transfer coefficients several are reviewed in Volume 2, Chapter 12. The two methods given in this section have been found to be reliable for preliminary design work, and, in the absence of practical values, can be used for the final design with a suitable factor of safety. 

The effectiveness—NTU method is a procedure for evaluating the performance of heat exchangers, which has the advantage that it does not require the evaluation of the mean temperature differences. NTU stands for the Number of Transfer Units, and is analogous with the use of transfer units in mass transfer see Chapter 11. 

The concentrations v, y refer to conditions on either side of the gas film, and hence Ng is the number of gas-film transfer units, and HG the height of a gas-film transfer unit. 

Mass Transfer Rates, Transfer Units, and Stage Efficiencies. 299... 

Sizing of a Cooling Tower Number of Transfer Units and Height of Tacking... 

Assembling the transfer unit takes -30 min. Electroblotting can be completed in 2 to 4 hr in most cases using a tank transfer unit and in -1 hr using a semidry blotting unit. 

The term B/kS may be interpreted as the height of a transfer unit and given the symbol H. Thus... 

There are two key variables that are difficult to calculate NG and NL (gas phase transfer units and liquid phase transfer units, respectively). The number of transfer units for each phase is calculated in terms of contact time and vapor rate. The contact times are determined... 

An alternative concept is the so-called direct absorption concept, which applies solar-receiver reactors. According to this concept a solar reformer was developed by DLR in the SOLASYS project (Tamme, 2003) based on earlier experiences in the projects SCR and CAESAR (Bauer, 1994). It allows the concentrated radiation to penetrate through a transparent aperture into the reformer, where it is absorbed directly by the irradiated absorber. The reaction gases pass through the absorber which serves simultaneously as a heat transfer unit and as support for the catalyst. The quartz window, used as aperture closure, enables the reformer to be operated under pressure. A schematic of the solar receiver is shown in Figure 3 (right). The reformer was operated up to 0.9 MPa and 780°C. The pilot reformer was tested at a power level of about 300 kW(th) at the solar tower of the Weizmann Institute of Science in Rehovot, Israel. In a follow-up project SOLREF (Moller, 2006), the operation conditions will be about 1.5 MPa and 950°C. 

When Henry s law is valid [Eq. (lc)], Eq. (18a) can be analytically integrated alternatively, the graphical form shown in Fig. 8 can be used for evaluating Nqq. Expressions for cases in which the equilibrium curve cannot be linearly approximated are available in several texts, such as Hines and Maddox (1985). Figure 8 shows that the number of transfer units increases with the ratio ttiGm/ m When this ratio increases above unity, the number of transfer units, and therefore column height, rapidly increase ... 

An analytical solution is also available for theoretical stages as opposed to transfer units, and the height equivalent to a theoretical plate (HETP). The number of theoretical stages or plates Np can be determined by counting the steps between the operating line and the equilibrium line as is done with distillation problems (see Example 8.1 in Section 8, Distillation), but a more convenient analytical solution is as follows ... 

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