Units Operations: Processing and Handling

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    P.E. Review Session

    III-A. Unit Operations

    by

    Mark Casada, Ph.D., P.E. (Mech. Engr.)

    Lead Scientist and Agricultural EngineerUSDA-ARS

    Grain Marketing and Production Research Center

    Manhattan, Kansas

    [email protected]

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    NCEES Topics

    Unit Operations 8%

    Characterization of Biological Products 4%

    Processing & Handling

    Mass transfer between phases Principles of unit operations Standards, codes, and regulations Principles of postharvest storage

    (Covered previously)

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    Unit Operations

    What are Unit Operations?

    Common operations that constitute a process, e.g.:

    pumping, cooling, dehydration (drying), distillation,

    evaporation, extraction, filtration, heating, size reduction,and separation.

    How do you decide what unit operations apply to

    a particular problem? Experience is required (practice).

    Carefully read (and reread) the problem statement.

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    Principles of Unit Operations

    Mass BalanceInflow = outflow + accumulation

    Energy BalanceEnergy in = energy out + accumulation

    Specific equationsFluid mechanics, pumping, fans, heat transfer,

    drying, separation, etc.

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    IllustrationJam Production

    Jam is being manufactured from crushed fruit with14% soluble solids.

    Sugar is added at a ratio of 55:45

    Pectin is added at the rate of 4 oz/100 lb sugar

    The mixture is evaporated to 67% soluble solids

    What is the yield (lbjam/lbfruit) of jam?

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    IllustrationJam Production

    mJ = ? (67% solids)

    mf= 1 lbfruit (14% solids)

    ms =1.22 lbsugar

    mp =0.0025 lbpectin

    mv = ?

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    IllustrationJam Production

    mJ = ? (67% solids)

    mf= 1 lbfruit (14% solids)

    ms =1.22 lbsugar

    mp =0.0025 lbpectin

    mv = ?

    Total Mass Balance:

    Inflow = Outflow + Accumulation

    mf+ ms = mv + mJ + 0.0

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    IllustrationJam Production

    mJ = ? (67% solids)

    mf= 1 lbfruit (14% solids)

    ms =1.22 lbsugar

    mp =0.0025 lbpectin

    mv = ?

    Total Mass Balance:

    Inflow = Outflow + Accumulationmf+ ms = mv + mJ + 0.0

    Solids Balance:

    Inflow = Outflow + Accumulation

    mfCsf + msCss = mJCsJ + 0.0

    (1 lb)(0.14lb/lb) + (1.22 lb)(1.0lb/lb) = mJ(0.67

    lb/lb)

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    IllustrationJam Production

    mJ = ? (67% solids)

    mf= 1 lbfruit (14% solids)

    ms =1.22 lbsugar

    mp =0.0025 lbpectin

    mv = ?

    Total Mass Balance:

    Inflow = Outflow + Accumulationmf+ ms = mv + mJ + 0.0

    Solids Balance:

    Inflow = Outflow + Accumulation

    mfCsf + msCss = mJCsJ + 0.0

    (1 lb)(0.14lb/lb) + (1.22 lb)(1.0lb/lb) = mJ(0.67

    lb/lb)

    mJ = 2.03 lbJam/lbfruit

    mw = 0.19 lbwater/lbfruit

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    IllustrationJam Production

    mJ = ? (67% solids)

    mf= 1 lbfruit (14% solids)

    ms =1.22 lbsugar

    mp =0.0025 lbpectin

    mv = ?

    What if this was a continuous flow concentrator

    with a flow rate of 10,000 lbfruit/h?

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    Principles of Unit Operations

    Mass Balance:Inflow = outflow + accumulation

    Chemical

    concentrations:

    Energy Balance:

    Energy in = energy out + accumulation

    t

    Ci

    1m

    1,iC2,iC2m

    t

    T

    1m

    1T

    2T2mK

    KT

    m

    J/kgcapacity,heatspecificc

    e,temperatur

    kg/srate,flowmass

    p

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    Principles of Unit Operations

    Mass Balance:Inflow = outflow + accumulation

    Chemical

    concentrations:

    Energy Balance:

    Energy in = energy out + accumulation

    t

    C

    VmCmCi

    ii

    22,11,

    t

    TVcTcmTcm ppp

    2211

    (sensible energy)

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    Principles of Unit Operations

    Mass Balance:Inflow = outflow + accumulation

    Chemical

    concentrations:

    Energy Balance:

    Energy in = energy out + accumulation

    t

    C

    VmCmCi

    ii

    22,11,

    t

    TVcTcmTcm ppp

    2211

    (sensible energy) total energy = mh

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    Illustration Apple Cooling

    An apple orchard produces 30,000 bu of apples a year, andwill store of the crop in refrigerated storage at 31F.Cool to 34F in 5 d; 31F by 10 d.

    Loading rate: 2000 bu/day

    Ambient design temp: 75F (loading) decline to 65F in20 d

    Estimate the refrigeration requirements for the 1st 30 days.

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    Apple Cooling

    qfrig

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    Principles of Unit Operations

    Mass BalanceInflow = outflow + accumulation

    Energy BalanceEnergy in = energy out + accumulation

    Specific equationsFluid mechanics, pumping, fans, heat transfer,

    drying, separation, etc.

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    Illustration Apple Cooling

    qfrig

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    Illustration Apple Cooling

    qfrigenergy in = energy out + accumulation

    qin,1+ ... = qout,1+ ... + qa

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    Illustration Apple Cooling

    qfrigenergy in = energy out + accumulation

    qin,1+ ... = qout,1+ ... + qa

    Try it -

    identify: qin,1 , qin,2 , ...

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    Illustration Apple Cooling

    Try it...

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    Apple Cooling

    qr

    qm

    qm

    qb

    qsqe

    qso

    qfrig

    qin

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    Apple Cooling

    Sensible heat terms

    qs = sensible heat gain from apples, W

    qm = heat from lights, motors, people, etc., Wqso = solar heat gain through windows, W

    qb = building heat gain through walls, etc., W

    qin = net heat gain from infiltration, W

    qe = sensible heat used to evaporate water, W

    1 W = 3.413 Btu/h, 1 kW = 3413. Btu/h

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    Apple Cooling

    Sensible heat equations

    qs = mload cpA T

    qr = mtot Hresp

    qm = qm1 + qm2 + . . .

    qb = (A/RT) (TiTo)

    qin = (Qacpa/vsp) (TiTo)

    qso = ...

    0

    0

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    Apple Cooling

    definitions

    mload = apple loading rate, kg/s (lb/h)

    Hresp = sp. rate of heat of respiration, J/kgs (Btu/lbh)mtot = total mass of apples, kg (lb)

    cpA = sp. heat capacity of apples, J/kgC (Btu/lbF)cpa = specific heat capacity of air, J/kgC (Btu/lbF)

    Qa = volume flow rate of infiltration air, m3/s (cfm)

    vsp= specific volume of air, m3/kgDA (ft

    3/lbDA)

    A = surface area of walls, etc., m2 (ft2)RT = total R-value of walls, etc., m

    2C/W (hft2F/Btu)

    Ti = air temperature inside,C (F)

    To = ambient air temperature,C (F)

    qm1

    , qm2

    = individual mechanical heat loads, W (Btu/h)

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    Example 1

    An apple orchard produces 30,000 bu of apples a year, and willstore of the crop in refrigerated storage at 31F. Cool to34F in 5 day; 31F by 10 day.

    Loading rate: 2000 bu/day

    Ambient design temp: 75F (at loading)declines to 65F in 20 day

    A = 46 lb/bu; cpA = 0.9 Btu/lb

    F

    What is the sensible heat load from the apples on day 3?

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    Example 1

    qr

    qm

    qm

    qb

    qsqe

    qso

    qfrig

    qin

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    Example 1

    qs = mloadcpAT

    mload = (2000 bu/day 3 day)(46 lb/bu)

    mload = 276,000 lb (on day 3)

    T = (75F 34F)/5 = 8.2F/day

    qs = (276,000 lb/day)(0.9 Btu/lbF)(8.2F/day)

    qs = 2,036,880 Btu/day = 7.1 ton

    (12,000 Btu/h = 1 ton refrig.)

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    Example 2

    Given the apple storage data of example 1,

    = 46 lb/bu; cpA = 0.9 Btu/lbF;

    What is the respiration heat load (sensible) from the apples onday 1?

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    Example 2

    qr = mtot Hresp

    mtot = (2000 bu/day 1 day)(46 lb/bu)

    mtot = 92,000 lb

    qr= (92,000 lb)(3.4 Btu/lbday)

    qr= 312,800 Btu/day = 1.1 ton

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    Unit Operations Examples

    Sterilization (food engineering)

    Heat exchangers

    Evaporation (food engineering) Drying

    Postharvest cooling

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    First order thermal death rate (kinetics) ofmicrobes assumed (exponential decay)

    D = decimal reduction time = time, at a giventemperature, in which the number of microbes is

    reduced 90% (1 log cycle)

    tko

    DeNN

    D

    ttk

    N

    ND

    o

    ln

    Sterilization

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    Sterilization

    The z value is the temperature increase that will result in atenfold increase in death rate The typical z value is 10C (18F) (C. botulinum)

    Fo = time in minutes at 250F that will produce the same

    degree of sterilization as the given process at temperature T Standard process temp = 250F (121.1C)

    Thermal death time: given as a multiple of D Pasteurization: 46D

    Milk: 30 min at 62.8C (holder method; old batch method)15 sec at 71.7C (HTST high temp./short time)

    Sterilization: 12D

    Overkill: 18D (baby food)

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    Sterilization

    Thermal Death Time Curve(C. botulinum)(Esty & Meyer, 1922)

    t= thermal death time, min

    z T

    oFt)F250(

    10

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    Sterilization

    Thermal Death Time Curve(C. botulinum)(Esty & Meyer, 1922)

    t= thermal death time, min

    z = DTfor 10x change in t,

    FFo = t@ 250F (std. temp.)

    z

    z

    T

    oFt)F250(

    10

    2.7

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    Sterilization

    Thermal Death Rate Plot

    (Stumbo, 1949, 1953; ...)

    D = decimal reduction time

    tk

    o

    D

    eNN

    D

    t

    N

    N

    o

    ln

    0.01

    0.1

    1

    10

    100 110 120 130

    Temperature, C

    DecimalReductionTime

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    Sterilization

    Thermal Death Rate Plot

    (Stumbo, 1949, 1953; ...)

    D = decimal reduction time

    tk

    o

    D

    eNN

    D

    t

    N

    N

    o

    ln

    0.01

    0.1

    1

    10

    100 110 120 130

    Temperature, C

    DecimalReductionTime

    121.1

    0.2

    z

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    Sterilization equations

    z

    T

    T DD)250(

    250 10

    N

    NDF oo log250

    z

    FT

    o tF)250(

    10

    zCT

    o tF)1.121(

    10

    z

    TT

    D

    D o

    o

    log

    T

    T

    o

    oo

    D

    F

    D

    F

    N

    N

    log

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    Sterilization

    Popular problems would be:

    Find a new D given change in temperature

    Given one time-temperature sterilization process,find the new time given another temperature, orthe new temperature given another time

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    Example 3

    If D = 0.25 min at 121C, find D at 140C.z = 10C.

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    Example 3

    equation D121 = 0.25 min

    z= 10C

    substitute

    solve ...

    answer:

    z

    TT

    D

    D o

    o

    log

    C

    CCD

    10

    1401.121

    min25.0log 140

    min003.0140 D

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    Example 4

    The Fo for a process is 2.7 minutes. Whatwould be the processing time if the processing

    temperature was changed to 100C?

    NOTE: when only Fo is given, assume standard

    processing conditions:

    T = 250F (121.1C); z = 18F (10C)

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    Example 4

    Thermal Death Time Curve(C. botulinum)(Esty & Meyer, 1922)

    t= thermal death time, min

    z =D

    Tfor 10x change in t,

    CFo = t@ 121.1C (std. temp.)

    zT

    oFt)C1.121(

    10

    2.7

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    Example 4

    z

    T

    oFt)C1.121(

    10

    C10

    )C100C1.121(

    10min)7.2(

    t

    min348t

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    Heat Exchangers

    me TAUq D

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    Heat Exchangers

    me TAUq D lmTAU D

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    Heat Exchangers

    lmme TAUTAUq DD

    D

    D DD

    D

    TT T

    ln

    T T T T

    ln

    T T T T

    lnlm T

    T

    Hi Co Ho Ci

    T T

    T T

    Hi Ci Ho Co

    T T

    T THi Co

    Ho Ci

    Hi Ci

    Ho Co

    max min

    max

    min

    ( ) ( ) ( ) ( )

    counter parallel

    qTcmTcm CCCHHH DD

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    Heat Exchangers

    subscripts: H hot fluid i side where the fluid enters

    C cold fluid o side where the fluid exits

    variables: m = mass flow rate of fluid, kg/s

    c = cp = heat capacity of fluid, J/kg-K

    C= mc, J/s-K

    U= overall heat transfer coefficient, W/m2-K

    A = effective surface area, m2

    DTm = proper mean temperature difference, K orC

    q = heat transfer rate, W

    F(Y,Z) = correction factor, dimensionless

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    Example 5

    A liquid food (cp = 4 kJ/kgC) flows in the inner pipeof a double-pipe heat exchanger. The food enters theheat exchanger at 20C and exits at 60C. The

    flow rate of the liquid food is 0.5 kg/s. In the annualsection, hot water at 90C enters the heatexchanger in counter-flow at a flow rate of 1 kg/s.

    Assuming steady-state conditions, calculate the exittemperature of the water. The average cp of water is

    4.2 kJ/kg

    C.

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    Example 5

    Solution

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    Time Out

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    Reference Ideas

    Full handbook The one you use regularly

    ASHRAE Fundamentals.

    Processing text

    Henderson, Perry, & Young (1997),Principles of Processing Engineering

    Geankoplis (1993), Transport Processes

    & Unit Operations.

    Need Marks Suggestion

    Standards

    ASABE Standards, recent ed. Other text Albright (1991),Environment...

    Lower et al. (1994), On-Farm Drying and...

    MWPS-29 (1999),Dry Grain Aeration

    Systems Design Handbook. Ames, IA: MWPS.

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    Studying for & taking the exam

    Practice the kind of problems you plan towork

    Know where to find the data See presentation III-B

    (Characterization of Biological Products )

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    Example 5

    Solution90C

    60C

    ?

    20C

    wwwfff TcmTcm DD

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    Example 6

    Find the heat exchanger area needed fromexample 5 if the overall heat transfer coefficient

    is 2000 W/m2C.

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    Example 6

    Find the heat exchanger area needed fromexample 5 if the overall heat transfer coefficient

    is 2000 W/m2C.

    Data:

    liquid food, cp = 4 kJ/kgC

    water, cp = 4.18 kJ/kgC

    Tfood,inlet = 20

    C, Tfood,exit = 60

    CTwater,inlet = 90C

    mfood = 0.5 kg/s

    mwater= 1 kg/s

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    Example 6

    Solution

    lme TAUq D

    CCC Tcmq D

    90C

    60C

    71C

    20C

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    More about Heat Exchangers

    Effectiveness ratio (H, P, & Young, pp. 204-212)

    One fluid at constant T: R

    D

    Tlmcorrection factors

    a

    b

    inba

    aacooling

    C

    CR

    C

    AUNTU

    TT

    TTE

    ,,

    )(

    )(

    min,1

    21

    ),( YZFTAUq lm D

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    Evaporator (Concentrator)

    mS

    mFmP

    mV

    Juice

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    Evaporator

    Solids mass balance:

    Total mass balance:

    Total energy balance:

    PPFF XmXm

    PVF mmm

    PpPPgvVSfgSFpFF TcmhmhmTcm )(

    lblbion,ConcentratX

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    Example 7

    Fruit juice concentrator, operating @ T =120F

    Feed: TF = 80F, XF = 10%

    Steam: 1000 lb/h, 25 psia

    Product: XP = 40%

    Assume: zero boiling point rise

    cp,solids = 0.35 Btu/lbF, cp,w= 1 Btu/lbF

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    Example 7

    mS

    mFmP= ?

    mV

    Juice(120F)

    TF= 80F

    XF= 0.1 lb/lbTP= 120F

    XP= 0.4 lb/lb

    TV= 120F

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    Example 7

    Steam tables:

    (hfg)S= 952.16 Btu/lb, at 25 psia (TS= 240F)

    (hg)V= 1113.7 Btu/lb, at 120F (PV= 1.69 psia)

    Calculate: cp,mix= 0.35 X + 1.0 (1X)

    Btu/lbF

    cpF= 0.935 Btu/lbF

    cpP= 0.74 Btu/lbF

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    Example 7

    mS

    mFmP= ?

    mV

    Juice(120F)

    TF= 80F

    XF= 0.1 lb/lbTP= 120F

    XP= 0.4 lb/lb

    TV= 120F

    hg= 1113.7 Btu/lb

    hfg= 952.16 Btu/lb

    cpF= 0.935

    Btu/lbF cpF= 0.74 Btu/lbF

    hlbskgPPFFSSXmXm ,

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    Example 7

    Solids mass balance:

    Total mass balance:

    Total energy balance:

    PpPPVgVSfgSFpFF TcmhmhmTcm )()(

    PPFF XmXm

    PVF mmm

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    Example 7

    Solve formP:

    mP

    = 295 lb/h

    VgXFpFXPpP

    SfgSPhRTcRTc

    hmm

    )()1(

    )(

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    Mass Transfer Between Phases

    Psychrometrics

    A few equations

    Psychrometric charts(SI and English units, high, low and normal temperatures; chartsinASAE Standards)

    Psychrometric ProcessesBasic Components:

    Sensible heating and cooling

    Humidify or de-humidify

    Drying/evaporative cooling

    M T f B Ph

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    Mass Transfer Between Phasescont.

    Grain and food drying

    Sensible heat

    Latent heat of vaporization

    Twb

    Psychrometrics

    Moisture content: wet and dry basis, and equilibrium

    moisture content (ASAE Standard D245.6)Airflow resistance (ASAE Standard D272.3)

    M T f B Ph

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    Mass Transfer Between Phasescont.

    0

    5

    10

    15

    20

    25

    0 20 40 60 80 100

    Relative Humidity, %

    Equilib

    riumMoistureContent,%

    0C

    20C

    40C

    ASAE Standard D245.6 .Use previous revision (D245.4) for constants

    or

    use psychrometric charts in Loewer, et al., 1994

    M T f B t Ph

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    Mass Transfer Between Phasescont.

    Loewer, et al. (1994)

    M T f B t Ph

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    Mass Transfer Between Phasescont.

    Effect of temperature on

    moisture isotherms (corn data)

    0

    5

    10

    15

    20

    25

    0 20 40 60 80 100

    Relative Humidity, %

    EquilibriumMo

    isture

    Content,%

    0C

    20C

    40C

    D i P

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    Drying Processcont.

    rhe

    Twb

    TG To

    rho

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    Use of Moisture Isotherms

    Relative Humidity, %

    EquilibriumMoistureContent,%

    Air Temp.

    Grain Temp.

    Me

    rho

    To

    rhe

    Mo

    TG

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    Drying (Deep Bed)

    Drying grain (e.g., shelled corn) with the drying airflowing through more than two to three layers ofkernels.

    Dehydration of solid food materials multiple layers drying & interacting

    (single, thin-layer solution is a single equation)

    wb

    db

    db

    wbM

    MM

    M

    1

    11

    1

    )1()1( 2,21,1 wbwb MWMW

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    Grain Bulk Density

    kg/m3 lb/bu[1]

    Corn, shelled 721 56

    Milo (sorghum) 721 56

    Rice, rough 579 45

    Soybean 772 60

    Wheat 772 60

    1Standard bushel. Source: ASAE D241.4

    Basic Drying Process

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    Basic Drying ProcessMass Conservation

    Compare: moisture added to air

    to

    moisture removed from product

    Basic Drying Process

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    Basic Drying ProcessMass Conservation

    inaoutaa ,, D

    Fan

    grainofmasstotalgm

    ina,:ratiohumidity

    MCgraininchangeD gW

    outa,:ratiohumidity

    am

    Basic Drying Process

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    Basic Drying ProcessMass Conservation

    Try it:

    Total moisture conservation equation:

    Basic Drying Process

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    Basic Drying ProcessMass Conservation

    ggaa Wmtm DD

    Compare: moisture added to air

    to

    moisture removed from product

    Total moisture conservation:

    Basic Drying Process

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    Basic Drying ProcessMass Conservation

    ggaa Wmtm DD

    Compare: moisture added to air

    to

    moisture removed from product

    Total moisture conservation:kgas

    skgwkga

    kgwkgg

    kgg

    Basic Drying Process

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    Basic Drying ProcessMass Conservationcontd

    aa

    gg

    m

    Wmt

    D

    D

    Calculate time:

    Assumes constant outlet conditions

    but outlet conditions often change as product dries

    use deep-bed drying analysis for non-constant outletconditions(Henderson, Perry, & Young sec. 10.6 for complete analysis)

    D i P

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    Drying Process

    Assume falling rate period, unless

    Falling rate requires erh or exit air data

    Drying

    Rate

    Time

    Constant

    Rate Falling

    Rate

    erh = 100%aw = 1.0

    erh < 100%aw < 1.0

    EvaporativeCooling

    (Thin-layer)

    Drying Process

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    Drying Processcont.

    Twb

    Drying Process

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    Drying Processcont.

    Twb

    erh

    ASAE D245.6

    E l 8

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    Example 8

    Hard wheat at 75F is being dried from 18% to12% w.b. in a batch grain drier. Drying will bestopped when the top layer reaches 13%. Ambient

    conditions: Tdb = 70F, rh = 20%

    Determine the exit air temperature early in thedrying period.

    Determine the exit air RH and temperature at theend of the drying period?

    E l 8

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    Example 8

    Part II

    Use Loewer, et al. (1994 ) (or ASAE D245.6)

    RHexit = 55%

    Texit = 58FTwb

    emc=13%rhexit

    Texit

    E l 8

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    Example 8

    Loewer, et al. (1994)

    13%

    E l 8

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    Example 8

    Part I

    Use Loewer, et al. (1994 ) (or ASAE D245.6)

    Texit = Tdb,e = TG = 53.5F

    Twb

    emc=18%

    Tdb,e

    Cooling Process

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    Cooling ProcessEnergy Conservation

    Compare: heat added to air

    to

    heat removed from product

    Sensible energy conservation:

    gggaaa TcmTctm DD

    IIinitialg TTT D

    Cooling Process

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    Cooling ProcessEnergy Conservation

    Compare: heat added to air

    to

    heat removed from product

    Sensible energy conservation:

    gggaaa TcmTctm DD

    Total energy conservation:

    gggaa Tcmhtm DD

    IIinitialg TTT D

    Cooling Process

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    Cooling Process(and Drying)

    Cooling Process

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    Cooling Process(and Drying)

    Twb

    erh

    Airflow in Packed Beds

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    Airflow in Packed BedsDrying, Cooling, etc.

    Source: ASABE D272.3, MWPS-29

    Design Values for Airflow Resistance in Grain

    0.1

    1

    10

    100

    0.001 0.01 0.1 1 10

    Pressure Drop per Foot, inH2O/ft

    Airflow,cfm/ft

    2Corn (PF=1.5)

    Sunflower (PF=1.5)

    Soybeans (PF=1.3)

    Barle PF=1.5

    Wheat (PF=1.3)

    Milo (PF=1.3)

    Standards Codes & Regulations

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    Standards, Codes, & Regulations

    Standards

    ASABE

    Already mentioned ASAE D245.6 and D272.3

    ASAE D243.3 Thermal properties of grain and

    ASAE S448 Thin-layer drying of grains and crops

    Several others

    Others not likely for unit operations

    Fin l Th ht

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    Final Thoughts

    Study enough to be confident in your strengths

    Get plenty of rest beforehand

    Calmly attack and solve enough problems to passemphasize your strengths

    Plan to figure out some iffy problems AFTER

    doing the ones you already know

    Aeration Fan Selection

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    Aeration Fan Selection

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)LF x MS x (depth) + 0.5DP = (inH2O/ft)design x (depth) + 0.5

    4. Total airflow: cfm = (cfm/bu) x (total bushels)

    or: cfm = (cfm/ ft2) x (floor area)

    5. Select fan to deliver flow & pressure (fan data)

    Aeration Fan Selection

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    Aeration Fan Selection

    00.2

    0.4

    0.6

    0.8

    1

    1.2

    1.4

    0 500 1000 1500 2000 2500 3000

    Airflow, cfm

    StaticPressure,inH

    2O

    System

    Fan

    Aeration Fan Selection

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    Aeration Fan Selection

    Example

    Wheat, Oklahoma, fall aeration

    10,000 bu bin 16 ft eave height

    pressure aeration system

    Aeration Fan Selection

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    Aeration Fan Selection

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)LF x MS x (depth) + 0.5

    4. Total airflow: cfm = (cfm/bu) x (total bushels)or: cfm = (cfm/ ft2) x (floor area)

    5. Select fan to deliver flow & pressure (fan data)

    Aeration Fan Selection

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    Aeration Fan Selection

    Recommended Air f low Rates for Dry Grain

    (Foster & Tuite, 1982):

    Recommended rate*, cfm/bu

    Storage

    TypeTemperate

    Climate

    Subtropic

    Climate

    Horizontal 0.05 0.10 0.10 0.20

    Vertical 0.03 0.05 0.05 0.10

    *Higher rates increase control, flexibility, and cost.

    Select lowest airflow (cfm/bu) for cooling rate

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    Select lowest airflow (cfm/bu) for cooling rate

    Approximate Cooling Cycle Fan Time:

    Airflow rate (cfm/bu)

    Season 0.05 0.10 0.25Summer 180 hr 90 hr 36 hr

    Fall 240 hr 120 hr 48 hr

    Winter 300 hr 150 hr 60 hr

    Spring 270 hr 135 hr 54 hr

    Aeration Fan Selection

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    Aeration Fan Selection

    cfm/ft2 = (0.8) x (16 ft) x (0.1 cfm/bu)

    cfm/ft2 = 1.3 cfm/ft2

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    Aeration Fan Selection

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    Aeration Fan Selection

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)LFx MS x (depth) + 0.5

    4. Total airflow: cfm = (cfm/bu) x (total bushels)or: cfm = (cfm/ ft2) x (floor area)

    5. Select fan to deliver flow & pressure (fan data)

    Pressure drop: DP = (inH2O/ft) x MS x (depth) + 0.5(note: M = 1 3 for wheat)

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    (note: Ms = 1.3 for wheat)

    Airflow Resistance in Grain (Loose-Fill)

    0.1

    1

    10

    100

    0.0001 0.001 0.01 0.1 1 10

    Pressure Drop per Foot, inH2O/ft

    Airflow,cfm/ft2 Corn

    Barley Milo

    Soybeans

    Wheat

    0.028

    1.3

    Pressure drop: DP = (inH2O/ft)design x (depth) + 0.5

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    g

    Design Values for Airflow Resistance in Grain(w/o duct losses)

    0.1

    1

    10

    100

    0.001 0.01 0.1 1 10

    Pressure Drop per Foot, inH2O/ft

    Airflow,cfm/ft2 Corn

    Barley Milo

    Soybeans

    Wheat

    0.037

    1.3

    Aeration Fan Selection

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    Aeration Fan Selection

    DP = (0.028 inH2O/ft) x 1.3 x (16 ft) + 0.5 inH2O

    DP = 1.08 inH2O

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)LFx MS x (depth) + 0.5

    Aeration Fan Selection

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    Aeration Fan Selection

    DP = (0.037 inH2O/ft) x (16 ft) + 0.5 inH2O

    DP = 1.09 inH2O

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)design x (depth) + 0.5

    Aeration Fan Selection

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    Aeration Fan Selection

    cfm = (0.1 cfm/bu) x (10,000 bu)

    cfm = 1000 cfm

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)LF x MS x (depth) + 0.5

    4. Total airflow: cfm = (cfm/bu) x (total bushels)

    Aeration Fan Selection

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    Aeration Fan Selection

    1. Select lowest airflow (cfm/bu) for cooling rate

    2. Airflow: cfm/ft2 = (0.8) x (depth) x (cfm/bu)

    3. Pressure drop: DP = (inH2O/ft)LF x MS x (depth) + 0.5

    4. Total airflow: cfm = (cfm/bu) x (total bushels)or: cfm = (cfm/ ft2) x (floor area)

    5. Select fan to deliver flow & pressure (fan data)

    Aeration Fan Selection

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    Aeration Fan Selection

    SSStttaaatttiiiccc PPPrrreeessssssuuurrreee,,, iiinnn HHH222OOO

    MMMooodddeeelll 000""" 000...555""" 111""" 111...555""" 222...555""" 333...555"""

    111222""" 333///444 hhhppp 111999000000 111666777555 111222999000 888111555 333222555 000

    111222""" 111 hhhppp 222333000888 111999666333 111444666000 888777666 333000555 000

    111444""" 111...555 hhhppp 333111333222 222888555222 222555222666 222111222666 111000444000 000

    Axial Flow Fan Data (cfm):

    Aeration Fan Selection

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    Aeration Fan Selection

    Selected Fan:

    12" diameter, hp, axial flow

    Supplies: 1100 cfm @ 1.2 inH2O

    (a little extra 0.11 cfm/bu)

    Be sure of recommended operating range.

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