Page 233 - Applied Process Design For Chemical And Petrochemical Plants Volume II

222 Applied Process Design for Chei mica1 and Petrochemical Plants

F = Free height in downcomer above clear liquid level = Aerated tray, liquid pressure drop or equivalent
(not froth level) clear liquid on tray, in. tray liquid
F, = Tower velocity factor hli = Height of clear liquid on inlet side of tray, in.
Fflood = Flood factor, dimensionless hio = Height of clear liquid at overflow weir, in.
Fh = vo6& for perforated trays, no downcomers h, = Depth of notch in weir, in.; or
FP = F1, = Flow parameter, dimensionless = Head in the back of downcomer, in. (usually negli-
F, = Hole factor = v,, (pv)1/2 gible)
F, = Vapor flow parameter based on active area, defined how = Height of liquid crest over flat weir; or measured
by F, = Va p+/', or from weir (straight or circular); or from bottom of
= Tra F factor based on active (bubbling) area = v, notches (v-notch weir), in.
p; Y * (ft/sec) (lb/ft3)lI2 how' = Height of liquid above bottom of notch in notched
Fw = Modification factor to weir formula weir, in.
=
FW = Flow parameter, dimensionless hop = KP Valve lift, Le., distance between bottom of a
G = V = Vapor or gas flow, lb/hr (see Figures 8-82 or 83, or valve and top of the tray deck, in.
Equations 8-219 or 290); or hpc = Cap assembly partial pressure drop, including drop
= Gas mass velocity, lb/hr-ft2 through riser, reversal, annulus, slots, in. liquid
g = Acceleration of gravity, 32.2 ft/sec-sec h, = Pressure drop through risers, in. liquid
Hw = Maximum lift of a valve, in. h, = Pressure drop through reversal and annulus, in.
Hd = Height of clear liquid in downcomer, in. liquid
H, = Slot height of bubble cap, in. h, = Slot opening, or pressure drop through slot, in. liq-
=
(HTE)oG Height of transfer unit, ft uid
HETP = Height equivalent to a theoretical plate/tray/stage, h', = Pressure drop through dry slots, in. liquid
in. or ft, or possibly mm h,l = Static liquid seal on sieve tray, in. liquid
h, = Head loss due to bubble formation, in. liquid; or h,, = Static slot seal, in.
= Head loss due to vapor flow through perforations, h,, = Height of cap shroud ring, in.
in. liquid h, = Total vapor pressure drop per tray, in. liquid (wet
h = Height of overflow weir or bubble cap riser, tray)
whichever is smaller, in. hdc = Head loss due to the underflow clearance, in.
hal = Height of aerated liquid on tray, in. hv = Maximum vertical travel of a valve on a valve tray,
metric
he, =Wet cap pressure drop (riser, reversal, annulus, h, = Height of weir above tray floor (to top of flat weir,
slots), in. liquid
or bottom of notch in notched weir), in.
h, = Head of liquid in bubbling zone; wet cap pressure hw = Wet tray head loss, in. liquid
drop; or taken as in. clear liquid on tray
h', = Total dry cap pressure drop, in. liquid K, = Constant for Bolles' partial bubble cap pressure
drop equation, Figure 8-1 14; or
hd = h, = Height of clear liquid on tray, in. (or mm) = Loss coefficient, valve closed, (sec)z(in.)/(ftZ)
b,i = Clear liquid at the inlet, in. L = L' = Liquid flow, lb/hr or lb/sec (or m3/hr/m
h, = Clear liquid height at froth-to-spray transition, in. weir length); or
liquid (or mm) = Liquid rate, lb/hr (ft2 active late/tray)
hd = Total head loss under downcomer, in. liquid Lbc = Liquid mass velocity, lb/hr-ft B based on superficial
h'd = Head loss between segmental downcomer and tray cross section of column
inlet weir, in. liquid L/V = Internal reflux ratio, dimensionless
hdc = Head loss of cirdar down-pipe at point of greatest Lwi = Weir length, in.
restriction, in. liquid I.9 = Liquid flow'rate, Tm = Q
hdd = Downcomer height clearance between bottom of lf = Liquid flow rate, ft /sec
downcomer and tray floor, in. I& = L, = Total flow width across tray normal to flow, ft
hdl = Dynamic liquid seal on sieve or perforated tray, in. 1, = Length of straight weir, ft
liquid 1,' = lfp = Length of liquid flow path, ft
hd, = Dynamic slot seal, in. liquid mmp = Vapor rate, lb/sec
hdt = Pressure drop through dry perforated or sieve tray, m = Exponent in CCFL correlation, or Equation 8327,
in. liquid equals approx. 1 .O
hdu = Downcomer head loss due to friction and under- N = Total number of actual trays in tower
flow, in. liquid N, = Number of caps per tray
he - Effective liquid head taking aemtion of liquid into N, = Number of slots per bubble cap
account, in. liquid, Figure 8130 Nv = Valve density, number of valves per ft2; or
hf = Height of top of foam above tray floor, in. (or mm) = Number of valve units on a valve tray
hf' = Height of free fall of liquid in downcomer; in. or n = Depth of notches in weir, in; or
= Height of froth on tray (aerated mass), in. = Exponent defined by Equations 8-288 and 327
hfd = Downcomer backup, in. AF' = Dry tray pressure drop for 50% cut baffles, in. liq-
hh = Head loss due to vapor flow through perforations, uid per baffIe; or
in. liquid; or = Actual tray pressure drop, in. liquid
= Dry tray pressure drop, in. liquid Pr = Prandtl number dimensionless
hL = Clear liquid head, m Pv = Fractional opening in the circumference or a valve;
hl = Depth of clear liquid on tray, inches; (or m); or or, PI