HETP height-equivalent theoretical

HETP height equivalent to theoretical plate, m HTU height equivalent to a transfer unit, m... 

Packing material can be plastic, metal, or ceramic. Packing efficiencies can be expressed as HETP (height equivalent to a theoretical plate). 

HETP = height equivalent to a theoretical plate, ft HTU = height of a transfer unit, ft L = liquid mass velocity, Ib/hr-ft m = exponent a 1.0 n = exponent 0.44 Pr = Prandtl number, dimensionless Sc = Schmidt number dimensionless U, = linear velocity of gas based on total column cross-sectional area, ft/sec... 

HETP = Height equivalent to a theoretical plate/tray/stage, in. or ft, or possibly mm... 

FP = flow parameter, dimensionless HETP = height equivalent of a theoretical plate, in. 

The HETP (Height Equivalent to a Theoretical Plate (stage or plate)) is the tray spacing divided by the fractional overall tray efficiency [82]. The transfer unit concept has been useful for generalized correlations [89]. Because packed towers operate with continuously changing compositions through the packed height, the concept... 

HETP = height equivalent to a theoretical plate, inches Hog = height of an overall gas phase transfer unit, inches... 

Before releasing a process column for chromatography, it is advisable to perform some test to measure efficiency, such as calculating height equivalent theoretical plates (HETP), both to forestall any problems in the column bed and to provide a benchmark by which to measure column reproducibility and predict degradation of the bed or material. Examples of compounds that are relatively innocuous for use in pharmaceutical applications are 1% NaCl (for gel filtration), concentrated buffer solutions (for ion exchange), and benzyl alcohol and parabens for reverse phase LC.10... 

HETP = height equivalent to a theoretical plate. It is derived from the plate theory of distillation which is a confusing concept having no basis in fact in the context of modem chromatographic separations. Nevertheless the terms plate number and plate height are still very widely used. 

The properties of a fractionating column which are important for isotope separation are (1) the throughput or boil-up rate which determines production (2) HETP (height equivalent per theoretical plate) which determines column length (3) the hold-up per plate which determines plant inventory and time to production (4) the pressure drop per plate which should be as small as possible. The choice of a particular column is invariably a compromise between these factors. The separation in a production column is of course less than it would be at total reflux (no product withdrawal). The concentration at any point in the enriching section can be calculated from the transport equation (see, e.g., London 1961)... 

HETP Height equivalent to a theoretical plate (or tray). Also called an equilibrium separation stage. 

FIGURE 22 Dependence of height equivalent theoretical plate (HETP) on flow velocity at different temperatures on a Chiralcel OJ CSP. (From Ref. 9.)... 

HETP Height equivalent to a theoretical plate. A measure of the combined effects of axial mixing and finite mass transfer resistance in causing deviations from ideal (equilibrium) behavior in a chromatographic column or in a countercurrent contact system. The definitions of HETP in these two cases are somewhat different,... 

Distillation stage calculations are usually performed with ideal stages, The number of ideal stages required for the separation is divided by the overall column efficiency (Sec, 7,1,1) to obtain the required number of trays. In packed towers, the number of stages in the column is multiplied by the HETP (Height Equivalent of a Theoretical Plate, see Sec. 9.1,2) to obtain the packed height. 

The concept of HETP (height equivalent of a theoretical plate) was introduced to enable comparison of efficiency between packed and plate columns. HETP iB defined as... 

The separation between two successive equilibria is called a theoretical plate. If this is a height H along some physical column, it is called the height-equivalent theoretical plate (HETP). 

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