Agitating Vessel

8/13/2019 Agitating Vessel

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Design of agitated

Heat transfer vessel


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GROUP MEMBERS

SABA 06-CHEM-02

FARIHA 06-CHEM-16

SHAZIA 06-CHEM-38


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Dual Shaft Paste Mixer

The Dual Shaft Mixer includes

an Anchor agitator and a HighSpeed Disperser. The anchorfeeds product into the highspeed disperser blade and

ensures that the mixture isconstantly in motion. Theanchor can be provided withscrapers to remove materials

from the interior vessel walls toenhance the heat transfercapabilities of the mixer. Bothagitators are available forvariable speed operation


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Dual Shaft Paste Mixer
http://www.lab-mixers.com/default.asp


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Jacked and coil heat transfer agitatorvessel


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Heat transfer coil in side vessel


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Use of baffles


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Applications

Mixing tanks are typically used in the productionof viscous fluids such as petroleum, plastics,paints, paper, cosmetics, and food. Themechanical agitation of fluid in these vessels can

significantly increase the rate of heat transferbetween the process and cooling fluids. Sincethe 1950s, a number of authors have exploredheat transfer for Newtonian fluids in a variety ofagitated vessel configurations. There has been a

limited amount of research performed, however,for heat transfer to non-Newtonian (power law)fluids.


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chemical, food, drugs dyes and otherindustries


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Use for Pharmaceutical Application


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used in chemical and pharmaceutical industries

h i l l i & dh i


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Petro-Chemical, Polymers,Coatings & Adhesives,Agricultural & General Chemicals,Plastics&Rubber

,Food & Beverage Industry.


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Homogeneous Batch/Semi-batchReactions

Homogeneous batch/semi-batch are themost common reaction type. They can beas simple as adding measured quantities

of two or more reactants to a vessel andmixing. Heat is normally removed oradded through a jacket, heating mantle or

external heat exchanger


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Data Given

Liquid Properties:

Cp = 0.6 Btu/(lb) (O

F)k= 0.1Btu/(hr)(sq.ft)(OF/ft)

= 1000cp (at80F)

=60lb/ft3 = 8.02lb/galCp,k and are assumed to be constant


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Steam properties:

hs=1000 Btu/(hr)(sq.ft)(OF)

Vessel Properties:

Wall thickness= 0.125 in

K of vessel = 9.4 Btu/(hr)(sq.ft)(OF/ft)

Eq used for calculating heat transfer coefficientNNU= 0.73(NRE)

0.65(NPR)0.33(w/ b)

0.14


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STEP 1:

Diameter of the vessel DT=6 ft.6-ft diameter agitated vessel conforming to

standard configuration as shown in the figure.The vessel is equipped with the 2 ft diameter 6-

blade, flat-blade turbine impeller running at 100rpm.

Diameter of impeller = 2ft

Impeller blade width=0.5 ft

Impeller blade height=0.4 ft

Baffle width=0.6 ft


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STEP 2:

Inside area of the vessel = DL (L=D)

= 3.14(6)(6)

= 113 ft2


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STEP 3:

Reynolds number evaluation at

80F,130F,180F by using,

NRE= N Di2/

Here, we assume density to be constant

over the temperature range.

Viscosity values at different temperatures is;

(80F) = 1000cp (from table)(130F) = 270 cp

(130F) = 84cp


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Diameter of impeller, Di= 2 ft

From these values , the Reynolds number is,

NRE(80F) = (60)(6000)(4)/(2420)

= 595NRE(130F)= 2200

NRE(130F)=7080


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STEP 4:

The Prandtl number calculations at

80F,130F,180F are,

NPR= CP/k

NPR (80F) = (0.6)(2420)/(0.1)

= 14500

NPR (130F) = 3920NPR (180F) = 1220


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STEP 5:Approximate the value of inside

heat transfer coefficient from givenequation;

NNU= hiDT/k = 0.73(NRE)0.65(NPR)

0.33

substitutingthe appropriate values into thisrelationship gives:

hi(80F) =18.4 Btu/(F) (hr) (sq.ft)

hi(130F) =27.6 Btu/(F) (hr) (sq.ft)

hi(180F) =40.4 Btu/(F) (hr) (sq.ft)


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STEP 6:

The wall temperature from the above heat

transfer coefficients are calculated andused to evaluate the viscosity of liquid atvessel wall

The wall temperature is estimated fromthe approximate equation:

TW= TS [(TS-TB)/1+(hsAO/hiAi)]

here, AO= Ai


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Solving wall temperature

TW (at TB = 80F) = 209.6 F

TW (at TB = 130F) = 209.8 FTW (at TB = 180F) = 210.7 F

Viscosity values at different temperatures is;(209.6F) = 47cp (from table)

(209.8F) = 47cp

(210.7F) = 46 cp


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Calculate the viscosities ratios equals to

w/ b

At TB=80F and TW= 209.6F

VIS=47/1000=0.047


VIS=47/270=0.174


VIS=46/85=0.541


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STEP 8:

1/Ui = 1/hi+ x/k +1/hs

hi= as calculated in step 7x= 1/8 in =0.0104 ft

K= 9.4 Btu/(hr)(sq.ft)(F/ft) for the vessel

wallhs= 1000 Btu/(F) (hr) (sq.ft)

Ui(Tb=80 F) =0.0281 Btu/(F) (hr) (sq.ft)Ui(Tb=130 F) =38.7 Btu/(F) (hr) (sq.ft)

Ui(Tb=180 F)= 42.5 Btu/(F) (hr) (sq.ft)


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Ui at different time intervals

35

36

37

38

39

40

41

42

43

0 50 100 150 200

Tb(F)

Ui Ui


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STEP 9:

Time taken to heat the liq over each tempincrement is calculated by this formula

Thr=(MCP/UiAi) ln [TS TI/TSTf]

Liquid mass= (Dt2/4)(Ht)()

= (36/4)(6)(60)

=10180 lb


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Time reqd to heat the nass from 80 to 100 F iscalculated as

t(80-100F)= (10180)(0.6) ln (212-80)

(36.15)(113) (212-100)

=0.242 hrt(100 -120F) = 0.283 hr

t(120 -140F) = 0.340 hr

t(140-160F) = 0.439 hrt(160-180F) =0.630 hr

Total Time = 1.934 hr


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Approximate method:

Thr=(MCP/UiAi) ln [TS TI/TSTf]

Thr=(10180*0.6/38.7*113)

*ln [212-80/212 -180]Thr=1.981 hr

Value differ by only 2.4%

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Agitating Vessel