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  • 8/9/2019 Mc Kee - Thermosiphon Reboileres a Review

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    HUGH

    R. McKEE

    latest holdup correlation proposed is the model of Levy

    55) with additional empirical relationships between

    variables established from actual data applicable to

    thermosiphons. Pressure-drop calculations follow the

    recommendations of Collier and He witt

    14)

    who found

    agreement with the Lockhart-Martinelli correlation

    below a liquid Reynolds number of 2100, and Cheno-

    weth-Martin ( 73) above 2100.

    Nucleation effects are

    considered as a function of liquid film thickness in the

    calculation of a maximum flux, thus relating these two

    design features to experimental d ata.

    A

    recent study by Tripathy

    (73)

    compared the pres-

    sure-drop calculation methods of Fair, Hughmark, and

    a shortcut method based on an overall average two-

    phase density, using data obtained on a 5/8 in., 1 6

    gauge, 4.5-ft tube, with w ater as the process fluid.

    Agreement was found best using Fair's method, ac-

    ceptable for Hughmark's method, a nd rather poor for

    the shortcut method. It was recommended tha t the

    designer follow the more sophisticated methods for

    other than very approximate work.

    Design Data Sources

    Overall design data, including both local heat-transfer

    coefficients and pressure-drop values, started appearing in

    the mid-fifties. Piret and Isbin (67) investigated six fluids :

    water, carbon tetrachloride, normal butyl alcohol,

    isopropyl alcohol, 35 wt

    %

    KzCOa, and 50 wt %

    KzCOa

    at atmospheric pressure in a 1-in. nominal copper tube

    with a heated length of 46.5 in. Th ey correlated th e

    inside heat-transfer coefficient by using a modified

    Dittus-Boelter equation

    where ha, is the inside average boiling coefficient,

    Urn is a log mean velocity assuming homogeneous

    flow equals (U mixture outlet

    -

    U liquid inlet)/ln

    erties (surface tension, viscosity, thermal conductivity,

    hea t capacity, a nd density, respectively), ur s the surface

    tension of water, and D is the characteristic length.

    Th e authors also correlated their dat a using t he superpo-

    sition technique of convection and pool boiling.

    Guerrieri and Talty

    (36)

    employed a light oil as a

    heating medium around a 0.75 in. i.d. by 6-ft long tube

    an d a 1.0 in. i.d. by 6.5-ft long tube. Inside wall an d

    boiling stream temperatures were measured at 6-in.

    intervals along the tubes. Film coefficients ar e pre-

    sented for methanol, cyclohexane, benzene, pentane,

    an d heptane atmospheric pressure as a function of the

    Lockhart-Martinelli parameter X t t . Wall tempera-

    tures were found generally to decrease from the bottom

    to the top of the tube. Stream- tempera ture distribu-

    tions displayed the expected maximum at some inter-

    media te point. Th e boiling film coefficient is also pre-

    sented in terms of a nucleate boiling correction factor.

    Dengler and Addoms

    18)

    used a

    1

    in. i.d. by 20-ft

    long copper tube in a forced convection study on water,

    using radioactive tracers to measure liquid fractions

    along the tube. The y present the ratio of the local co-

    efficient to the liquid-phase coefficient as a function of

    the reciprocal of the Lockhart-Martinelli parameter.

    The y observe an d discuss the suppression of nucleate

    boiling by forced convection either externally induced

    or

    vapor induced.

    Beaver and Hughniark (8) used an electrically heated

    3 4

    in. by 8-ft long carbon steel tube to investigate the

    reliability of using developed correlations in vacuum

    operations. Th e authors decided tha t for wall minus

    saturation temperature differences less than 15°F single

    phase coefficients dominate and can be predicted by a

    modified Dittus-Boelter equation (Sieder-Tate modifica-

    tion)

    [ u o u t / u i n l ,

    UL PL kz , Cz, PL are liquid phase prop-

    Nu

    =

    0.023

    (Re)'J.*

    (Pr)0.4

    [ . 1 4

    Steam

    Thermosiphon

    Reboi ler

    Tubes

    Figure

    7. Vertical thermosiphon

    reboiler

    VO L 6 2

    NO.

    1 2

    D E C E M B E R

    1 9 7 0 77

  • 8/9/2019 Mc Kee - Thermosiphon Reboileres a Review

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    Nucleation occurs for temperature differences greater

    than 15°F and local inside coefficients can be predicted

    by existing two-phase correlations. Investigations

    covered a total of twelve fluids, and the observed liquid

    circulation rates are presented ; this allows the designer

    to compare calculated an d experimental liquid rates.

    Lee et

    al. 53)

    sed a reboiler consisting of se\wi tubes

    in a bundle. Th e tubes \ve x 1 in. o.d., 14 gauge, 10-ft

    long Admiralty metal. Dat a for a total of s e ~ e niquids

    are presented for pressure ranges of approxiniatcly 2

    to

    120 psia. T h e authors present overall coefficients

    as

    functions of overall temperature differences. The aver-

    age inside-film coefficient and tlie niaxiriiuiii flux are

    presented in terms of dimensionless groups. The niaxi-

    mu m flux

    vas

    found for each fluid and system pressure.

    Above the niaximuni flux, vapor lock occurred; it \vas

    the departure from smooth cocurrent

    f low

    of the two

    phases through tlie equipment. Recoininendations

    include a inaximurii overall coefficient of 500 Btu jh r

    s q f t O F , an d the need for giving particular atrention to

    reboiler entrance an d exit piping.

    Johnson (46) measured circulation rates and overall

    temperature driving forces for a 15-in. shell reboiler

    con-

    taining 96

    1

    in., 1 2 gauge, 8-ft long tubes. One tube was

    equipped with a temperature probe

    to

    obtain local boil-

    iiig stream temperatu res. Circulation rates wer e pre-

    dicted by Kern's method. This method assumes a linear

    variation of specific volume Tvith leng th in

    the

    vapor-

    ization zone, and that heat transfer proceeds from

    the

    wall

    to

    the liquid and then

    to

    the vapor ca\.ities. T he

    Lockhart-h,lartinelli parame ter is used in t h e calculation

    of friction and expansion losses for the two-phase zonc.

    Overall coefficients, driving forces, fluxes, flow, and

    vaporization rates are tabulated for water and a hydro-

    carbon having a normal boiling point of

    80. 8 C.

    Typ-

    ical temperature profiles are show711 for six runs on the

    hydrocarbon. Overall temperature differcncc predic-

    tions are compared to the work of Piret and Isbin (67).

    Data on 44 runs are included.

    Shelleiie et

    al. (69)

    also used an industrial-size reboiler

    having a 14-in. shell, containing 70 3/4 in., 13 gauge, and

    3 7/ 8 in., 12 gauge, 8-ft long tubes, providing 110 s q

    f t

    of area . The reboiler was connected to

    an

    existing dis-

    tillation column and, except for instrunlentation, was

    identical to a typical coriiniercial unit. The hcat sourcc

    was steam, and the process fluids \vex benzene, water,

    isopropyl alcohol, methyl ethyl ketone, glycerine, and

    various aqueous solutions of the alcohol, ketone, and

    glycerine. Of parti cular interest in the work was the

    exploration

    of

    the onset of unstable operation. Th e

    authors found t ha t rhe addit ion of flow resistance

    to

    the

    inlet line extended the srable operating range and: as

    might be expected, the allowable pressure drop across

    the tubes decreases as the heat flux increases. Resis-

    tances were also added to the vapor return line, which

    resulted in a decrease in the niaxirnuni flux as the resis-

    AUTHOR Hugh R. McKee

    is with

    Born Engineering Co mp an y,

    P.0 ox 102, Tu l sa , Okla . 74101.

    tance increased. The resulting rccoiiiiiiciidation o

    keeping

    t h e

    return line flow area cqual

    to

    the tubc fl o

    area was consistent with t ha t of Giliiiorc

    (L31) .

    Max

    imum lieat fluxes are tabulated for the various fluids with

    accoiiipanying ie inper ature differences and

    c;/c

    17aporiza

    tion. Other data are prescntcd as

    flux

    us. log nieai

    temperature differciic,e and mass x-clocity us. pressur

    drop. This work will be invaluable for design and

    coin

    parison purposes, an d it

    shows

    that an opportunily cxist

    for a n experi inen talist to iiivestiga tc the contribution o

    the various componcnis in the flow loop to stablc opcra

    rion. Emphasis to da te has

    been

    placed on

    the

    hcat.cd

    elenient of the loop, ivhicli

    is

    certainly justified. Th e

    designer also needs to be sure that his filial proposal wil

    meet both heat transfer

    arid

    stable operation rcquirc

    men s.

    Research into boiling heat-transfer cocf-licients ha

    been rather recent, and a s

    y e t

    no coiiiplctcly reliable

    correlation h a s evolved, a s it has for single p h a s e flow fo

    various geometries.

    Table I is a brief suiiiiiiary

    of

    typical boiling data in

    tcrnis of the more coiniiionly investigated fluids. W h e n

    lack of a siinilar fluid-surface coiiibination

    is

    encountered

    particular attention should be givcn in riiatchiny sur

    faces when using a generalized correlation. Fluid prop-

    erty variations are adequately described in inost cor

    relations, the surface characteristic remaining inde

    pendent. Unfortunately, the best one can do is

    rc i i ic i i i

    ber that the type

    of

    surface is iiiiportant i n boiling hea

    transfer, and remain alert to clcvelopinents in this arca.

    Schrock aiid Grossman (68) correlated local hcat

    Lransfer cocfficients for the

    lorccd

    f l ow of water in the

    wettcd-wall rcgion---i.e., between subcoolcd boiling and

    the traiisition to dry wall conditions-in tcrnis of the

    Lockhart-hlartin elli parameter and the boiling nuliibcr

    The boiling num ber is the hcat flux cli\rided by the prod

    uct of

    the

    m a s s flux aiid rhc latent heat of vaporization

    Local pressure gradients are presented

    as

    functions of a

    niodified Lockhart-hlartinclli parameter

    where p is the viscosity. 17 is the specific volume. x is the

    fraction vapor. and F efers to saturatcd liquid.

    Experiinents \ \ere perforiiied on tubes 0.116 2 to

    0.4317 in. i.d

    ,

    15-

    to 40-111.

    long, Tlith hcat fluxcs of

    6 X

    l o 4 to 1 . 4 5

    X

    l o GBtu/lir

    f t 2 .

    inav fluxes

    of

    49 to

    911

    lb/sec f t L , and system pressures from 42 to

    505

    psia

    The authors rccornrriend their correlation for cxit qual-

    ities up to

    50%

    A niax imuni coefficient was observed by Groothius an d

    Hendal (35) a t the suspected transition from slug to

    niist-annular flow. Th e authors were in\-estigating two-

    phase heat transfer in air-water and air-gas oil mixtures.

    Th e conditions for the riiaxirnurn coefficient arc related

    to a dimensionless group deri\-ed from the IVeber nuiii-

    ber . Local coefficients are presented in terms of

    S u ,

    Re

    Pr, and viscosity rati o.

    The concept of superposition of heat-transfer inecha-

    78 I N D U S T R I A L A N D E N G I N E E R I N G C H EM IS T RY

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    TABLE I NUCLEATE B OIL ING CORRELATIONS

    Surface

    Stainless steel

    Comments

    low

    pattern

    Inside horizontal, vertical

    Fluid

    Aniline

    Aniline

    Generalized correlation

    independent of flow pat-

    tern

    Brass

    Chromium

    304 Stainless

    Stainless steel

    Copper

    Annular

    Pool boiling

    Pool boiling

    Inside horizontal, vertical

    Benzene

    13.5 to 48.8 psia

    Data from 14 runs

    -Butyl alcohol

    Alcohol, n butyl

    Data from 15 runs

    arbon tetrachloride

    Cyclohexane

    Diphenyl

    Copper

    Brass

    304 Stainless

    Annular

    Pool boiling

    Pool boiling

    Pool boiling, axial, and

    twisted tape swirl flow

    Alcohol, ethyl ethanol

    Ethylene glycol

    Copper

    347 Stainless

    A-nickel

    Copper and stainless steel

    Atmospheric pressure

    Burnout data included

    Freon 11, 113

    Heptane

    Inside horizontal

    Annular

    Pool boiling

    Pressure drop da ta included

    Polished chromium

    Hydrogen

    Isopropyl alcohol

    Alcohol, isopropyl

    Methyl alcohol

    Alcohol, methy l

    Mercury

    11 correlations

    Data from

    1 4

    runs

    opper

    Annular

    Inside tubes, across flat

    plate

    Annular

    1 and

    3

    atm

    30"-78"K temperature

    range

    30'-78 OK tempe rature

    range

    Neon

    Copper, nickel, cadmium

    Copper, nickel, cadmium

    Pool boiling

    Annular

    Pool boiling

    Annular

    Inside horizontal and

    vertical

    Nitrogen

    Pentane

    Potassium carbonate,

    35% and 50%

    Stainless steel

    Nickel

    Data from 15 runs length-

    wise temperature profile

    included

    65-400 mm Hg abs

    1200°-15000F

    Sodium Horizontal disk

    Pool boiling

    Pool boilingeta-terphenyl, ortho-

    terphenyl, 4.35y0 pura-

    terphenyl in meta-ter-

    phenyl (Santowax-

    Monsan o)

    Water

    Inside vertical tubesopper

    Oth er correlations Boiling

    Two-phases (gas-liquid)

    Review

    22,

    23,

    24,

    71)

    69)

    66)

    nisms was modified by Chen (72) to account for the sup-

    pression effect of the moving fluid on the boiling rate.

    The conditions of convective heat transfer are met at the

    limits of 0% and

    1 0 0 %

    quality, and in the boiling, two-

    phase region the interaction between the mechanisms

    is accounted for. I t

    is

    at this point that empiricism

    enters the model, that is, in the determination of the

    interaction effect. Chen's appr oac h provides the de-

    signer with a method of obtaining a forced con-

    vection boiling coefficient with a min imum of model

    detail considerations.

    Other generalized boiling correlations have been pre-

    sented by Levy 54, Gilmore (31), and Forster and

    Greif

    (25).

    Boiling curves and correlations are also to

    be found in the general review

    of

    boiling by Westwater

    (79,

    80).

    Pressure effects on boiling curves have been

    studied by Mendler

    e t

    al . (63).

    For those

    who

    insist on climbing the nucleate boiling

    VOL.

    6 2

    NO.

    1 2 D E C E M B E R 1970

    79

  • 8/9/2019 Mc Kee - Thermosiphon Reboileres a Review

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    curve as far

    as

    possible, a grea t deal of attention has been

    given to the critical flux, first boiling crisis or burnout

    point. This riiaxiiiiuiii nucleate boiling flux is slightly

    above the DNB (departure from nucleate boiliiig) point.

    The area

    is

    unreliable in ternis of stability and repro-

    ducibility. On e easily slips over into either the transi-

    tion region or the film-boiling region, with a resultant

    decrease in the flux. Thi s critical flux

    is a

    point the

    designer should respect enough

    to

    check a nd avoid.

    Bergles et a l . ( 9 ) investigated the critical hcat flux for

    water at low pressures (below 100 psia ). They iiivesti-

    gated the effects of tube lengt h, inler temperature , tube

    diameter, and pressure on the critical heat flux. Th c

    authors relate their results

    to

    the instabilities of th e slug-

    flow regime. Critical heat fluxes for water a re normally

    considered to start around 0 . 4

    X

    l o 6

    Btulhr ft’;

    ho\v-

    ever, the authors have shown values of half this amount

    und er low pressure conditions.

    Gaiiibill

    (28)

    has kept abreast of the critical flux liter-

    ature in ternis of general rcvie\vs (27) , aiid in the prc-

    sentation of a corrclation. Th e latter correlation

    is

    based

    on

    two

    ternis,

    a

    forced convection term and

    a

    boil-

    ing term. Gaiiibill has also demonstra ted the uncer-

    tainty i n predicting the critical flux ( 2 9 ) . If one needs

    to be impressed xvith the magnitude of the problem, the

    latte r reference is suggested.

    Boiliiig curves and critical fluxes for some binary

    liquids have been presented by

    van

    tVijk

    t al.

    75) or

    benzene, toluene, and acetone for both pool boiliiig, aiid

    for forced convection lengthwisc outsidc tubes by Carne

    I ). Pressure effects on the critical flux have been in-

    \-cstigated by Hoxvell and Bell

    (37) .

    Th e designer then

    h a s

    the usual problem of selecling

    which approach to utilize, empirical or theoretical.

    Fair

    (22)

    describes these approaches as the statistical

    approach of Iliighniark, arid his o i vn riiechanistic ap-

    proach. Th e former presents sccurity to the, dcsigner,

    if

    siiiiilar coiidir ioiis can be found betwxen his prob lem

    and the contributing data . T he advaiitage of the rnech-

    anistic approach lies

    in

    extrapolation into the unknown.

    Th e soft spot in Fair’s nierhod is in

    the

    selection of a boil-

    TABLE

    I I .

    VERTICAL FLOW TWO-PHASE

    CORRELATIONS

    jsteni

    Comments Rejerence

    Introductory survcy ( 7 7 )

    Survcy advocating

    Dukler’s

    Energy equation discussion

    Film thickncss, film

    f low

    rate

    Air-lvat er Pressure drop and holdup

    study comparison with ex-

    Pressure drop in slug flow, ex-

    Elevated pressure effects, cx-

    (20, 21)

    approach (76)

    (theory) (76, 74)

    .lir-Water

    study 30.1

    perimcntal dat a 1 7

    perimciital study (33)

    perimeiital study 1631

    .\ir-\Vater

    Boiling water

    -

    ing coefficient, which places one in the wonderland o

    boiling da ta . The most benevolent advice to the d

    signer in selecting a boiling coefficient is to adopt Hug

    mark’s attitude and search for an appropriate boilin

    curve that represents identical fluid propcrties

    and

    su

    face characterisLics.

    Pressu re Drop

    Calcu la t i ons

    First, it should be mentioned that several valuab

    works are available for reference purposes in tkvo-pha

    flow. Kepple an d Tun g

    (47)

    have absrracted the lite

    ature for the period 1950- 1962. Grouse (34) has als

    classified a large amo unt of the tLvo-phase lit era ture.

    Anderson and Russell (2, 3,

    4 )

    present

    a

    thrce-pa

    survey of nvo-phase floxv. Parr I deals with

    f l ow

    pattern

    encountered in two-phase flo\v, an d how to predict thes

    floiv pat terns for horizontal and \,ertical

    f l ow

    For ve

    tical

    f l o ~ ,

    he slug-flow regime envelope (between bubb

    and annular mist), is presented as thc voluiiietric g

    fraction of

    the

    entering fuel streaiii ZJS. a gas-liqu

    Froude nuniber. 4 econd correlation is also presente

    a s

    the liquid superficial velocity

    us.

    the gas-liquid vol

    iiictric ratio at input, which

    is

    divided into the bubbl

    slug, fro th, ripple, an d film-flow regimes.

    Part I1 considers the prediction of pressure drop

    two-phase f l ow. The authors recommend Dukler’s (2

    27) method as a general approach

    and

    they also fin

    favor in Hughmark’s 43) ethod

    as

    applied to eith

    horizontal o r vertical f l ow.

    Part

    I11

    coiicerns itself with a review of the status

    inass transfer, heat transfer, and clieinical reaction

    tlvo-phase f l ow (Other pertinent references arc pre

    scntcd in Table 11.)

    Hsu and Graham (38) forced water through

    13-

    an

    1~-11111i ubes Lvith boiling in an effort to gain soiiie insig

    into the niechaiiisiri of boiling inside tubes. Th e force

    floiv produces a scarcity of nucleation sites and a co

    responding small bubbly f l ow region. Coiivcciioii slu

    f l o ~ v a large hot layer forining vapor instead of bubb

    coalescence

    to

    form slugs) occurs rapidly, forming a lon

    Tay lor bubble. Bubble trajectories into the stream ar

    compared

    to

    jet rrajectories, aiid an actual trajector

    from high-spced motion picture studies

    is

    shown. T h

    change from bubble to slug aiid ann ula r flow is compare

    to the adiabatic map : ( r7,j

    (

    JTL+ V , )

    ZJS.

    Fr, whe

    Fr

    =

    ( V ~ + V J 2 / ( D g ) ,V is velocity, D is characteristi

    leng th, an dg is acceleration of gravity), not too favorabl

    Th e slug to annular

    f l ow

    transition occurred ax

    a

    dinien

    sionless vapor velocity Ut*

    =

    0.417 M-hich, according

    Wallis (78) should take place at

    G,*

    = 0.525, (U,*

    U / d G where

    U

    equals superficial vapor velocity).

    The calculation of the void fraction is dependent up01

    the relative velocity ratio between the phases (velocit

    slip rat io) , which is unknown. Von Glahn (77) corrc

    lated all xhe available steam-water data froin th e literatur

    in the form of an empirical equation that needs

    to

    b

    tested on other s>-stems. Hughmark (47, 42) also h

    been busy in the holdup correlation area. Xicklin e t a

    (65) investigated the rise velocity of bubbles in a one-in

    8 0 I N D U S T R I A L A N D E N G I N E E R I N G

    C H E M I S T R Y

  • 8/9/2019 Mc Kee - Thermosiphon Reboileres a Review

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    tube . Equa tions are presented for the velocities in slug

    flow as approximations below Re

    =

    8000, and accurate

    above Re

    =

    8000.

    Th e dimensionless group approach as employed by the

    petroleum industry in two-phase flow problems has been

    discussed by Baker

    (5).

    Th e work of Lockhart and Martinelli (56) has been

    modified innumerable times, which only seems to attest

    to its utility. Chenoweth and Marti n

    (73)

    extended the

    Lockhart-Martinelli work to larger straight pipes and

    included flow through some fittings.

    Dukler et a l . (20, 27) have presented a review of two-

    phase pressure drop. The conclusion of (20)was that the

    Lockhart-Martinelli correlation showed the best agree-

    men t with reality of t he pressure-drop correlations tested,

    and the holdup correlation of Hughmark (42) or holdup

    calculations was best. Hughmark's correlation

    is

    a

    modifica tion of one proposed by Bankoff 6),which as-

    sumes a high bubble concentration at the center of the

    stream, decreasing to zero at the wall for bubble flow.

    The slippage between the phases also is assumed zero,

    which is the single fluid model assumption. Th e model

    is applied to stream qualities for zero

    to

    60%.

    Following the work of Bankoff, we have the salvation

    of two-phase flow by Zuber and Findlay (87). They

    considered both the velocity and concentration profiles

    across the duct, along with the relative velocity between

    the phases in arriving at a holdup correlation.

    The

    result

    is

    a correlation that

    is

    independent of flow regime;

    however, it is limited to two-phase systems in which no

    phase change occurs by evaporation, condensaiion, boil-

    ing, or chemical reaction.

    Davis

    ( 7 5 )

    modified the Lockhart-Martinelli param-

    eter using the Froude number to accommodate the hori-

    zontal to vertical flow geometry change. Lockhart-

    Martinelli :

    Revised Lockhart-Martinelli parameter by Davis :

    where V, is the mean velocity of the liquid-vapor mix-

    ture, D s the diameter, and g c is the gravitational con-

    stant.

    The Davis correlation for pressure drop ( 0%)

    is

    applicable to the same pressure range as the Lockhart-

    Martinelli correlation : for the turbulent-turbulent flow

    regime with liquid Reynolds numbers above 8000, and

    the vapor Reynolds numbers above 2100 ; for liquid Reyn-

    olds numbers between 6000 and 8000, providing the

    vapor flow rate is great enough to obtain a Froude num-

    ber above 100.

    The inclusion of interfacial roughness considerations

    into the Lockhart-Martinelli correlation improved the

    pressure-drop prediction, as shown by McMillan et

    al .

    (62). Among the fluids used in horizontal systems was

    trichloromonofluoromethane.

    Baroczy (7) modified the Lockhart-Martinelli two-

    phase pressure drop gradient ratio,

    r li2,by

    considering

    the ratio of the two-phase gradient

    to

    the total liquid

    gradient

    In terms of the mass fraction (quality) vapor or gas

    This two-phase friction multiplier has been correlated

    for substances of a wide range of properties, in terms of

    a property index

    p

    and p are viscosity and density,

    respectively)

    with quality as the correlating parame ter. Th e autho r

    also presents a method for finding the two-phase pressure

    drop for changes in flow geometry, such as contraction-

    expansion, sharp-edged orifices, and other velocity-head

    related elements.

    Entrance effects and flow-transition effects for the slug-

    flow regime were considered by Moissis and Griffith 64

    in their description of the density distribution. Th e

    pressure drop is calculated

    to

    a first approximation for

    the final 20 pipe diameters.

    For work in which the critical pressure or above is

    liable to be encountered for homogeneous, two-phase

    flow, for appreciable AP, Paige

    (66)

    has presented three

    methods of calculating the pressure drop with a flashing

    liquid. Based on the use of average mixture densities

    and starting with the mechanical energy equation, the

    prediction of the pressure profile along the line is possible.

    The amount

    of

    effort being expended on two-phase

    flow is of an order of magnitude that allows

    us

    only to

    indulge in a selected bibliography. Th e game of com-

    parison quickly gets to be an infini tum of cornbinat ions.

    For example, Hughmark (43) has shown the similarity

    of form between the work of Lamb a nd White (57) and

    Hughmark and Pressburg (47). Pressure-drop expres-

    sions derived from a momentum balance result in a drag

    coefficient form. Energy balance derived expressions

    take on the lost work form.

    Hughma rk applies the latter

    to data for horizontal,

    vertical upward, and vertical

    downward flow for isothermal systems.

    Gill

    e t

    al . (30

    compare favorably with Lockhart-Martinelli for vertical

    upward flow of air-water.

    Conclus ions

    Th e standard of comparison seems to have been estab-

    lished by Lockhart -Martinelli. There must be some

    satisfaction in having produced the most often quoted,

    compared, an d modified work in the field. Th e Lock-

    hart-Martinelli standard appears not only in pressure-

    drop correlations, but also in two-phase coefficient cor-

    relations.

    There are several design methods currently available

    the classic local coefficient approach utilizing average

    conditions and properties in the two-phase region, the

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    statistical or empirical approach, and the more sophis-

    ticated method of Fai r. T he first

    is

    dangerous for the

    serious designer. Realistically a nd traditionally, the

    designer has functioned in the realm of experience and

    expedience. He, therefore, tends toward the second or

    empirical approach, which is highly useful for repeat

    rout ine work, b ut suffers from the limitation

    of

    producing

    questionable results when extrapolated beyond the con-

    ditions of the original da ta . Sufficient mater ial is now

    available to produce a satisfactory iriethod of design, if

    one remembers that investigations into areas such as f low

    control are still incomplete.

    The

    more theoretical ap-

    proach overcoines the extrapolation limitation, but

    d e -

    mands more effort to successfully set up the calculating

    procedure. The ubiquitous piper seems

    to

    be demand-

    ing his due for the pleasure of flexibility.

    REF

    E

    R ENCES

    1 j

    Anderson, G. H.

    and hl antzourdni s,

    B. G.. "T>\o-Ph;isc (G'is-Liquid)

    I'low

    ( 2 )

    hndcrson:

    R.

    J . and Russcll, T . IV. F., "Dcsigning for Tso-Phab c Floi*," Pa rt

    ind

    Russcl l ,

    T .

    IV. F..

    "Dcsigning

    l or

    Tuo-I'hdsc

    Florc,

    I'.iri

    (4)

    Anderson,

    R .

    J . and

    Russcll, T.

    I V . F., "Designing for 'Two-l'htiic Flow," P x t

    (5)

    Bakcr.

    O. ,

    Design of Pipclincs for Simultaneous Flow

    of

    Oil

    and

    Gas," 011 Gas

    (6)

    Bankoff.

    S. G . : \ ari,rble Density Sing le Fluid

    h l od r l for

    T\r.o-l'h,tic Flov with

    ( 7 ) Barocrv C. J.,

    A

    Syatem,itic Corrcl.ition for Two-Ph.ise I'ressurc Drop,"

    (8)

    Bcaver, P. R. . ind Hughm,irk. G . I,,lIC/ii:

    J . >

    4

    j), 46- 749

    (Scpt.

    1968).

    9) Berglcs. :\.

    E.,

    LopinSi: I . cr. l i ,

    52,

    37-46

    (1956).

    -Liquid) Systems: Hc. r

    Transfer

    a nd

    Hydraulics, An

    Annotntcd

    Bibliogr.ip

    ,lrgonne .Vul. Lair . , 67311

    July

    1964.

    (48) Krcith, I'. m i l Summcrficld, M , , "Presaurc Drop

    and Cun\cct icc

    Hea

    rr,insfer with

    Surf,icc

    Boiling

    'it

    Hiqh Hcat

    F l ux ; D . R-742

    (Fcb

    1 9 6 2 ) .

    (79) \Veitwatcr, J. I ',, "Boiling of Liquids,"

    n

    hdvanccr in Ch cmicd I,nginecring,

    Vol.

    I ,

    Academic Prcss lnc ., Kew

    York, 1956.

    (80)

    \Vest\\.atcr: J. W.,bid.,Vol.

    11,

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    (81)

    Zubcr, N. and

    Findlay,

    J

    Phase

    Flow Systems,"

    .J .

    Hea

    T h e s i a , Dcpt. of Chem. Cng., Th e Univcrsity of Tuls .~, 'ulsa, Okl.i., 1967.

    "A\-cragc Volumetric Conccntration in T wo-

    n s j c r ,

    87C ( 4) , 453-468

    (Nov.

    1965) .

    82 I N D U S T R I A L A N D E N G I N E E R I N G C H EM I ST R Y