Flow Characteristics of Mashed Beet

J . agric . Engng Res . (1996) 65 , 165 – 174

Flow Characteristics of Mashed Beet

M . Tu ̈ rk ; * G . Ho ̈ rnig ; * J . Beck ; † A . Deininger ; † T . Jungbluth †

* Institute of Agricultural Engineering Bornim , D – 14469 Potsdam , Germany

† University of Hohenheim , Institute of Agricultural Engineering , D-70599 Stuttgart , Germany

( Recei y ed 1 6 September 1 9 9 4 ; accepted in re y ised form 2 7 May 1 9 9 6 )

Knowledge of the flow characteristics of mashed beet during storage in tower silos , unloading , mixing and pumping through pipelines is fundamental for the handling of liquid beet silage , for possible feeding techniques and for plant design . Storage and flow properties of dif ferent varieties of beet and feed mixtures were investigated in relation to their dry matter content . The flow of fresh mashed beet through pipes is only possible due to wall slip ef fects . Experimental results are presented together with calculation methods for pressure losses . New software has been developed for planning pipeline systems applicable to dif ferent agricultural fluids and suspensions . ÷ 1996 Silsoe Research Institute

1 . Introduction

Liquid preservation of root crops by lactic acid fermentation allows production of high-quality con- centrate feed without use of chemical additives and low feed losses . 1 The central processing step is mash- ing the cleaned roots in a beet mill to produce a liquid beet mash with a consistency comparable with apple- pure ́ e . Beet mash can be transported , without addi- tional water , by displacement pumps into a hermeti- cally sealed tower silo . There , the beet pure ́ e ferments under anaerobic conditions into a stable silage with a pH lower than 4 in 8 – 10 d . It is taken out all year round by a rotary piston or worm pumps . The mash is fed with success both pure or in mixtures in solid or liquid form to cattle and pigs . 2–4

A knowledge of rheology and the flow behaviour of mashed beet during storage , unloading , mixing and pumping is fundamental for possible feeding techniques and plant design . Flow characteristics of fresh mashed beets and ensiled beets without additives have not yet been investigated systematically . Comparable

Presented at Ag Eng 94 , Milan , Italy , 29 August – 1 September 1994

Notation

A k , A n , B k , B n Rheological coef ficients of Eqns (8)

and (9) d Inside pipe diameter , m

H g e o Geodetic height , m k Fluid consistency coef ficient of power

law , Pa s k r Pipe roughness , mm D l Length of measurement pipes , m n Flow exponent of power law

N p Rotational speed of pump , rev min 2 1

p d Pressure after pump , kPa p s Pressure before pump , kPa P e Electrical power input of pump drive ,

kW D p / D l Specific pressure drop , Pa m 2 1

Q Volume flow rate , m 3 h 2 1

r Correlation coef ficient Re Reynolds number

Re crit Critical Reynolds number at laminar- turbulent transition

TS Total solids or dry matter content , % T Temperature , 8 C t Storage time , d y Flow velocity , m s 2 1

g ~ Shear rate , s 2 1

g ~ n Newtonian shear rate , s 2 1

h Dynamic viscosity of Newtonian liquids , Pa s

h s Apparent viscosity , Pa s h p l Plastic viscosity of Bingham model ,

Pa s l Pipe friction factor r Density , kg m 2 3

τ Shear stress , Pa τ w Wall shear stress , Pa τ 0 Yield stress , Pa

165 0021-8634 / 96 / 100165 1 10 $25 . 00 / 0 ÷ 1996 Silsoe Research Institute

M . T U ̈ R K E T A L . 166

investigations were however carried out in 1975 with chemically preserved sugar beet chips at the Institute of Agricultural Engineering in Bornim . 5

This paper concentrates on handling processes . Investigations were carried out on the behaviour of the material in a tower silo during storage , because of juice separation and also on pumping , mixing and tube flow behaviour of ensiled beet mash and feed mixtures . Rheological characteristics of beet mash play a central role and the overall objective is to model the flow properties .

Flow properties have been measured both with a laboratory scale rotary viscometer with a large shear gap and with a tube viscometer at a more practical scale . The results of the experiments are presented and discussed .

2 . Materials and methods

2 . 1 . Materials

The harvested root beets are dry-cleaned and washed in special cleaning machines . Afterwards the cleaned roots are chopped and mashed without air contact in a beet mill . The mill consists of a feeding auger , two rotating knives (1000 rev min 2 1 ) and a coarse and a fine screen matrix serving as cutting edges . A rotary piston pump is attached directly to the beet mill so that air contact is minimized . Mashed beets are known to behave as non-Newtonian suspensions with characteristic structural properties , similar to those of highly viscous agricultural materials . 5

Rheological properties must be investigated in an integrated way so that the shear stresses that arise in processing can be realized . Substantial errors may appear in calculations and applications if this principle is not observed .

The flow behaviour can be modelled by means of known power laws such as those for pseudo-plastic materials (Table 1) . Beet juice has always been assumed to show Newtonian flow behaviour . Beet mash has a relatively small particle size , which en- larges considerably if it is mixed with concentrates such as bruised grain . Beet mash also has a great ability to bond liquid and release it under pressure . Pipe flow of fresh mashed beets is assisted by wall slip ef fects . Depending on the shear stress , the mashed beet is pressed against the pipe wall and releases liquid similar to a sponge , such that the beet plug can slip more easily on the liquid layer adjacent to the wall . 5

The experiments were carried out using fodder beet with total solids TS < 8% , fodder sugar beet with

TS < 15% and sugar beet with TS < 21% (see columns 1 and 2 of Table 2) . The TS content of fresh mashed beets is about 2 – 4% higher than that of ensiled beets depending on preservation losses . The juice has only a 3 – 5% lower TS content than mashed beet and therefore it is a valuable feed component . The pipe flow experiments were carried out both with fresh mashed and ensiled beets . In some cases , step by step water or beet juice was added to ensiled beets to dilute the mixture (see column 3 of Table 2) .

2 . 2 . Experimental apparatus and methods

The storage experiments were carried out in six vertical glass cylinders (diameter 0 ? 2 m , height 3 m) . The object was to observe the separation processes of dif ferent beet varieties to draw conclusions about the removal of liquid silage mash out of a tower silo .

The experimental mixing and conveying equipment ( Fig . 1 ) is used to test mixers , pumps and pipelines . Pipe and pump characteristic curves were measured in the same experiment at a scale of 1 : 1 , that is , full size . The experimental plant consisted of a weighing mixer , a pump with engine unit and dif ferent plastic and steel measurement tubes . It was possible to use various liquid feed mixtures . Some of these have coarse particles and constitute highly concentrated suspensions with non-Newtonian flow properties . Problems of flow behaviour in displacement pumps and tubes were investigated and the liquid feed was characterized rheologically .

The following parameters were measured .

Volume flow rate ( Q ) with an electromagnetic flow meter . Electrical power input ( P e ) and speed ( N p ) of the pump . Dif ferential pressure ( D p ) over a measurement tube length D l 5 4 ? 0 m of plastic and steel tubes with dif ferent inner diameters ( d ) . The static pressure on the pipe wall is transmitted by a rubber diaphragm and silicon oil filled flexible tubes to an electric dif ferential pressure meter . Pressure before ( p s ) and after the pump ( p d ) . Material temperature before the pump ( T ) .

The measured values are transformed into digitized form , saved and analysed by a computer . The pump speed was varied with a frequency control system .

The measurement pipes constituted a tube-type rheometer . The basic assumptions are that flow is laminar and there is no wall slippage . We carried out nine pipeflow experiments with dif ferent substrates (see column 1 of Table 2) and always four or five

Tab

le 1

Rhe

olog

ical

cla

ssifi

cati

on a

nd p

ress

ure

drop

cal

cula

tion

for

lam

inar

and

tur

bule

nt p

ipe

flow

of

agri

cult

ural

sus

pens

ions

Fri

ctio

n fa

ctor

l

Flo

w be

ha y i

our

Flo

w m

odel

τ 5

f ( g ~ )

App

aren

t y i

scos

ity h

s ( g ~ n

) R

eyno

lds

num

ber

Re

Lam

inar

Tur

bule

nt

Ne

wto

nia

n

τ τ

Pse

ud

op

last

ic

n <

1

n >

1D

ilata

nt

(1)

Lin

ea

r p

last

ic(2

) N

on

lin

ea

r p

last

ic

τ τ o

2

1γ. γ. γ.

New

ton

τ 5

h g ~

h s (

g ~ n ) ;

h

Tra

nsit

ion

regi

on C

oleb

rook

equ

atio

n : 6

1 4

l 5

2 2

log 1 0

F 2 ? 51

Re

4 l

1 k r d

0 ? 26

92 G

Ost

wal

d-de

Wae

le

τ 5

k g ~ n

h s (

g ~ n ) 5

k S 3 n

1 1

4 n D n g ~ n

2 1

n R

e 5

y d r

h s (

g ~ n )

Re c

rit 5

2000

– 300

0

l 5

64 Re

n 5

1 : B

lasi

us e

quat

ion 6 f

or s

moo

th t

ubes

:

l 5

0 ? 31

6 R

e 0 ? 25

n ,

1 : si

mpl

ified

Dod

ge-M

etzn

er e

quat

ion :

7

l 5

a Re b

a 5

0 ? 31

26 n

0 ? 11

07

b 5

0 ? 25

14 n

2 0 ?

2118

(1)

Bin

gham

τ 5

τ 0 1

h p l

g ~ h

s ( g ~ n

) 5 τ 0

d 6 y

1 h

p l T

u ̈ rk-

Eck

sta ̈ d

t eq

uati

on : 8

(2)

Her

sche

l-B

ulkl

ey

τ 5

τ 0 1

k g ~ n

h s (

g ~ n ) 5

τ 0 d

2 π y

1 k S 2 π

y

d D n

2 1

l 5

C ( n

) (l

og 1 0

Re)

m ( n

)

C ( n

) 5 0 ?

9147

n 2 ?

2632

m ( n

) 5 2 ?

4407

1 3 ?

2379

log 1

0 n

M . T U ̈ R K E T A L . 168

Table 2 Measuring variants and rheological flow parameters of beet mash

Flow parameters Material TS range

%

Dilution Pipe material / diameter

mm

Density r

kg m 2 3 A K Pa s

B K —

A n —

B n —

Fresh mashed Fodder beet Fodder sugar

beet Sugar beet

9 ? 3 18 ? 1

23 ? 9

— — — —

p A , B p A , B s C , D p A , B s D

667 790

561

k 5 16 ? 55 k 5 78 ? 56 k 5 96 ? 49 k 5 304 ? 37 k 5 429 ? 47

0 0 0 0 0

n 5 0 ? 3972 n 5 0 ? 3532 n 5 0 ? 2512 n 5 0 ? 1518 n 5 0 ? 0405

0 0 0 0 0

Ensiled

Fodder beet 7 ? 2 – 8 ? 0

4 ? 8 – 7 ? 7

juice (TS 5 5 ? 4%)

water

p A , B s D p A , B s C , D

1549 – 73 ? 7 3 TS

1057 – 0 ? 52 3 TS

1 ? 681 0 ? 0036 0 ? 1066 0 ? 1595

0 ? 3064 1 ? 257 0 ? 7418 0 ? 7156

2 ? 631 1 ? 369 0 ? 9756 0 ? 7798

0 ? 3060 0 ? 2150 0 ? 1570 0 ? 1860

Fodder sugar beet

11 ? 3 – 13 ? 3

10 ? 0 – 15 ? 1

juice (TS 5 8 ? 9%)

water

p A , B s C , D p A , B s C , D

1038 – 0 ? 71 3 TS

1116 – 12 3 TS

4 ? 67 3 10 2 5

5 ? 64 3 10 2 5

0 ? 7757 1 ? 325

1 ? 047 1 ? 384 0 ? 3436 0 ? 3033

2 ? 425 2 ? 445 0 ? 7383 0 ? 4115

0 ? 1760 0 ? 1690 0 ? 0850 0 ? 0450

Sugar beet 10 ? 0 – 18 ? 0 water p A , B s C

1089 – 7 ? 56 3 TS 0 ? 1251 0 ? 1014

0 ? 4179 0 ? 4024

1 ? 707 1 ? 209

0 ? 1320 0 ? 0920

Pipe material : p plastic s steel

Pipe diameter : A d 5 56 ? 74 mm Pipe diameter : C d 5 53 ? 35 mm

B d 5 80 ? 67 mm D d 5 82 ? 32 mm

dilutions . Altogether about 160 graphs each with 20 to 30 measured values were analysed .

A specially designed rotary-type viscometer (RVG) with a large shear gap was developed in Bornim 9 and used for parallel measurements . Commercial rotary cylinder viscometers cannot be used for liquid feed because of their structure . The viscometer RVG has the following dimensions :

radius of inner cylinder (cup) radius of outer cylinder (bob) height of inner cylinder maximum Newtonian shear rate

138 mm , 158 mm , 400 mm , 70 s 2 1 .

The cup rotates with variable angular velocity and the resultant torque is measured at the inner cylinder . Inner and outer cylinder have a toothed surface to avoid wall slippage . For determining absolute flow curves of plastic materials in a large shear gap , a calculation method was developed . 10 The absolute flow curves are independent of the geometry of the rheometer .

3 . Results

3 . 1 . Storage beha y iour

Mashed beet ferments under anaerobic conditions to a stable silage with pH , 4 . Carbon dioxide is

produced during the fermentation process . The gas bubbles accumulate in the substrate and cause a flotation of beet mash . Juice and sediment collect at the bottom and are pumped out first from the silo . Fig . 2 illustrates , for fodder beet , the storage behaviour over 110 d , especially the stratification in the vertical cylinders , which was observed with three dif ferent beet varieties . In all cylinders a stabilization was registered after 7 to 10 d , such that foam forma- tion , as a result of fermentation , was reduced and the total height stayed constant .

In the cylinder of fodder beet the juice separation at the bottom started immediately . After 25 d a sediment layer consisting of smaller beet particles started to form . After 90 d , the liquid reached a maximum . The juice and sediment portion accounted for more than 50% of the total volume .

In the fodder sugar beet cylinder ( Fig . 3 ) less juice was separated . After 80 d , juice and sediment fractions reached 30% of the total volume . At 80 d the juice was carefully pumped from the bottom to the top of the cylinder . Only one week after pumping , the juice was located on the bottom again and the previous stable layers were restored . Therefore it is not possible to change the layers in the tower silo . Further- more , liquid beet mash was pumped around in a 6 m 3

tower silo to maintain a homogeneous beet mixture but only the juice flowed . It does not therefore seem

F L O W C H A R A C T E R I S T I C S O F M A S H E D B E E T 169

Q

T

pd

Pe Np

ps

∆p

∆p

∆p

∆p

∆p

d = 56·74 mm

d = 80·67 mm

d = 53·35 mm

d = 82·32 mm

d = 100·61 mm∆l = 4·00 m

Ribbonscrewmixer

Rotary-pistonpump

Frequency controlsystem

Pressure controlsystem

PVC tubes Pressuretransmitter

Steel tubes

Measurement tubes

Fig . 1 . Scheme of experimental equipment for mixing and con y eying of agricultural suspensions

possible to homogenize the mixture in a tower silo by circulation of the juice by means of a pump . Sugar beets did not show a noticeable juice layer even after 100 d of storage .

3 . 2 . Flow characteristics

Volume flow rate Q and dif ferential pressure D p were measured in the dif ferent pipes and Fig . 4 shows

specific pressure drop versus volume flow rate for fresh beet mash in plastic tubes . Sugar beet mash reached the limit of flowability . The wall shear stress ( τ W ) and Newtonian shear rate ( g ~ n ) were calculated using Eqns (1) and (2)

τ w 5 D p D l

d 4

(1)

g ~ n 5 32 Q

3600 π d 3 5 8 y

d (2)

3000

2500

2000

1500

1000

500

00 10 20 30 40 50 60 70 80 90 100 110

Storage time, d

He

igh

t in

st

ora

ge

cyl

ind

er,

mm

Total height

Mash

Juice

Sediment

Fig . 2 . Storage beha y iour of ensiled fodder beet mash in a y ertical cylinder , TS 5 9 ? 8 %

M . T U ̈ R K E T A L . 170

3000

2500

2000

1500

1000

500

00 10 20 30 40 50 60 70 80 90 100 110

Storage time, d

He

igh

t in

st

ora

ge

cyl

ind

er,

mm

Total height

Mash

JuiceSediment

Juice pumped

Fig . 3 . Storage beha y iour of ensiled fodder sugar beet mash in a y ertical cylinder , TS 5 1 7 ? 2 %

Figure 5 shows the flow curves for fresh beet mash in plastic tubes , that is , wall shear stress τ w versus Newtonian shear rate g ~ n . For laminar tube flow and no wall slippage the flow curves of dif ferent measurement tubes must lie on top of each other . That is a simple test for agreement with the main rheometrical rules . The dif ferent measured values shown in Fig . 5 are due to wall slip ef fects in tubes of dif ferent inner diameters and dif ferent flow velocities . The real shear rate ( g ~ ) at the tube wall may be calculated by the Rabinowitsch – Mooney equation for laminar flow 7 as given by Eqn (3) below .

g ~ 5 f ( τ W ) 5 3 S 8 y

d D 1

D p D l

d 4

d S 8 y

d D

d S D p D l

d 4 D

(3)

The gradient of the flow curve in logarithmic form is

50

40

30

20

10

0 0 5 10 15 20 25

Volume flow rate, Q , m3h–1

Spe

cific

pre

ssur

e dr

op, ∆p

/∆l,

Pa

m–1

Fig . 4 . Measured data and calculated pipe characteristic cur y es of fresh beet mash in plastic tubes . Specific pressure drop y ersus y olume flow rate . Fodder beet . 5 6 ? 7 mm , , 8 0 ? 7 mm ; Fodder sugar beet j 5 6 ? 7 mm , h 8 0 ? 7 mm ; Sugar

beet d 5 6 ? 7 mm , s 8 0 ? 7 mm

constant

n 5 d (ln τ W ) d (ln g ~ n )

(4)

The real shear rate at the tube wall is obtained in summarized form by means of the known Newtonian shear rate for pseudoplastic materials

g ~ 5 g ~ n S 3 n 1 1 4 n

D (5)

For determining the flow behaviour of fresh mashed and ensiled beet the simple power law according to Ostwald and de Waele of Eqn (6) can be applied with suf ficient confidence (Table 1)

τ W 5 k g ~ n (6) or in logarithmic form

ln τ W 5 ln k 1 n ln g ~ (7)

Using Eqn (7) , the fluid consistency coef ficient k and

700

600

500

400

300

200

100

00 50 100 150 200 250 300

Wal

l she

ar s

tres

s,τ w, P

a

Newtonian shear rate, γn, s–1.

Fig . 5 . Flow cur y es for fresh beet mash in plastic tubes . Wall shear stress y ersus Newtonian shear rate . Fodder beet m ;

Fodder sugar beet s ; Sugar beet d


flow exponent n can be calculated by linear regression . For these flow parameters , k and n were calculated as functions of the TS content by exponential regression using

k 5 A k exp ( B k TS) (8)

n 5 A n exp ( B n TS) (9)

These functions formed the basis for data files of rheological material parameters shown in Table 2 . Using the flow parameters of Eqns (8) and (9) shown in Table 2 , pipe characteristic curves were calculated for fresh beet mash flow in plastic pipes . Figure 4 shows that the calculated lines agree well with the measured values .

The flow curves ( Fig . 5 ) show that sugar beet had the greatest flow resistance problems because of its high dry matter content . The absolute limit of pumping is reached when the beet pulp does not flow voluntarily to the pump . Therefore , large air bubbles often occurred in the pipe and the volumetric pump ef ficiency was considerably decreased . The other beet varieties did not cause any flow problems .

The fermentation process reduces the dry matter content and improves the flow properties of the beet mash silage . The dif ferent beet varieties have clearly dif fering structural properties , which besides the other ingredients , decisively determine their flow behaviour ( Fig . 6 ) . With the so-called apparent viscosity we can describe these dif ferences simply . The apparent viscosity is defined by

h S 5 τ W ( g ~ )

g ~ n (10)

The apparent viscosity is calculated with the shear

App

aren

t vis

cosi

ty,η s

Pa

s

TS content, %

10

8

6

4

2

0 0 5 10 15 20

Fig . 6 . Apparent y iscosity y ersus TS content for beet mash silage of dif ferent y arieties . Fodder beet h ; Fodder sugar beet

n ; Sugar beet d

stress of Eqn (6) and the Newtonian shear rate according to Eqn (2) . In Fig . 6 the Newtonian shear rate of g ~ n 5 56 ? 6 s 2 1 is constant . This value results from a volume flow rate of Q 5 20 m 3 h 2 1 and inner pipe diameter of d 5 100 mm . In this way it is possible to draw a relative comparison between dif ferent materials and relevant influencing factors . The apparent viscosity is only correct for a constant shear rate .

Each apparent viscosity in Fig . 6 corresponds to a measured flow curve obtained in step by step water dilution . The form of the exponential function

h S 5 A exp ( B TS) (11)

is analogous to Eqns (8) and (9) above . The results of the conveying experiments are pre-

sented in the form of wall shear stress ( τ w ) versus Newtonian shear rate ( g ~ n ) for dif ferent TS contents ( Fig . 7 ) . The TS content plays a more important role in juice dilution than in water dilution as beet juice is a sugar solution with a TS of 6 – 9% . Table 2 contains the analysed flow parameters of several experiments corresponding to Eqns (8) and (9) for plant planning . Step by step , beet mash silage was diluted once with juice and once with water . Fresh beet mash was not diluted as the rheological properties quickly changed . Each of the rheological flow parameters which can be seen in Table 2 (columns 6 – 9) is associated statisti- cally with correlation coef ficients r . 0 ? 9 .

Pipe material has an important influence owing to wall slippage ( Figs 7 and 8 ) . Plastic pipes of the same inner diameter as steel pipes show a higher flow resistance , Fig . 7 . This phenomenon occurs as a larger pipe roughness results in a thicker wall slip layer and therefore in a lower flow resistance . A higher pipe

600

500

400

300

200

100

Wal

l she

ar s

tres

s,τ w, P

a

00 50 100 150 200 250 300 350 400 450 500

TS=15·1%

TS=13·7%

TS=12·6%

TS=11·7%

TS=10·5%

Wet

she

ar s

tres

s,

τ N, P

a


Fig . 7 . Flow cur y es of fodder sugar beet mash silage in plastic and steel tubes , diluted with water . Wall shear stress y ersus Newtonian shear rate . Plastic s d 5 5 6 . 7 4 mm ; Steel d

d 5 5 3 . 3 5 mm

M . T U ̈ R K E T A L . 172W

all s

hear

str

ess,

τ w

, Pa

350

0

300

250

200

150

100

50

0100 200 300 400 500


Rotational viscometerwith a large shear gap

Fig . 8 . Flow cur y es of fodder sugar beet mash silage ( TS 5 1 2 ? 6 % ) in plastic and steel tubes of dif ferent diameter . Wall shear stress y ersus Newtonian shear rate . Plastic m d 5 5 6 . 7 4 mm ; n d 5 8 0 . 6 7 mm ; steel d d 5 5 3 . 3 5 mm ; s d 5

8 2 . 3 2 mm

flow velocity leads to even greater wall slippage . Therefore the greatest dif ferences exist between plastic and steel tubes with the smallest diameter , Fig . 8 . A calculation method for wall slip correction was developed previously and applied to chemically preserved sugar beet chips . 5

Figure 8 shows that the measuring region of the rotational viscometer (RVG) is restricted , as regards both TS content and shear rate ( g ~ n , 70 s 2 1 ) . Shearing in the annular gap of the rotational viscometer is not comparable with tube flow especially because of wall slip ef fects . Therefore the measured flow parameters are used only as an estimate in planning works .

4 . Pressure drop calculation

The calculation of pressure losses is necessary in order to choose suitable pumping equipment . The calculation scheme shown in Fig . 9 is generally applicable for Newtonian and non-Newtonian agricultural fluids and suspensions . The rheological parameters given in Table 2 are used directly for dimensioning pipelines . At first an apparent viscosity is calculated with the help of a selected flow model . Depending on material form and TS content it is possible to select the best flow model (see Table 1) . The general Reynolds number is defined by using a viscosity function and in this form it is applied to every flow behaviour . At a critical Reynolds number Re crit > 2300 a continuous transition from laminar to turbulent flow takes place . Finally it is possible to calculate the specific pressure losses for laminar and turbulent

pipeflow by means of Eqn (12) . According to Bernoulli’s Eqn (13) it is then possible to calculate the total pressure of the pipe system ( p d ) .

D p D l

5 l r

2 y 2

d (12)

p d 5 O F D p

D l ( O l 1 O l * ) G

d 1 O ( y 2

i 1 1 2 y 2 i )

r

2

Ú H geo r g (13)

Local flow resistances of fittings and valves are considered with so-called equivalent pipe lengths ( l *) . The values were measured for sugar beet mash silage , 5

liquid feed and liquid manure and gathered in data files .

On this basis , a new Windows application software for the widely dif fering questions of process planning was developed . 11 The processing instructions serve as input data ( Fig . 9 ) . The calculated results are shown on the computer display in the form of pressure loss tables or pipe characteristic curves p 5 f ( Q ) . They can also be printed or saved . Data files of rheological material parameters exist for liquid manure and liquid feed of dif ferent compositions , which have been calculated in the last few years . This software is available at the Institute of Agricultural Engineering , Bornim .

5 . Conclusions

Storage , flow and conveying properties of ensiled beet mash were investigated to obtain basic data for material handling .

In a tower silo , stratification occurs . Mashed beet ferments under anaerobic conditions to a stable silage with pH , 4 . Carbon dioxide is produced in this process . The gas bubbles accumulate in the substrate and cause a flotation of beet mash . The juice collects at the bottom and is pumped out first from the silo . Circulation pumping cannot ameliorate the in- homogeneity as only the juice flows .

Without water addition , fresh mashed sugar beet can only be pumped through pipes owing to wall slippage . This is always the limit for pumping . Syste- matic pipeflow experiments were carried out with ensiled beets and liquid feed mixtures in plastic and steel pipes with dif ferent inner diameters . In addition step by step juice or water dilution experiments were carried out . The results of the conveying experiments are presented in the form of wall shear stress ( τ w ) versus Newtonian shear rate ( g ~ n ) for dif ferent total


Input data

(Material, TS, T;Q, d, Hgeo, kr )

Material fileFitting file

Selection offlow model

Newton(model 1)

τ = ηγ.Ostwald-de Waele

(model 2)τ = kγ n.

Herschel-Bulkley(model 3)

τ = το + kγ n.

Bingham (model 3)

τ = το + ηpl γ.

Apparent viscosityηs = f(γn, τo, k, n; T )

Pressure losses

Reynolds numberRe= vdρ

Friction numberλ = f(Re, n, k r )

Re < 2300laminar

Re > 2300turbulent

.

Output dataTable

GraphsFile

.

ηs(γn).

∆p∆l ρV2= λ 2d

Fig . 9 . Flow chart of pressure loss calculation for pipeline flow of agricultural suspensions

solids (TS) contents . The flow curves are approxim- ated with the Ostwald de Waele-power law . Empirical relations of flow parameters depending on TS content were devised to produce design information . The results are flow parameters for general rheological

characterization . Plastic pipes cause higher pressure losses than steel pipes because of wall slip ef fects .

A calculation scheme and new application software for planning works were developed for pressure loss calculations of liquid feed and liquid manure pipeflow .

M . T U ̈ R K E T A L . 174

Acknowledgements

This report is part of a joint research project of the Institute for Agricultural Engineering Bornim (ATB) and the Institute for Agricultural Engineering , University of Hohenheim , financed by the German Research Community (DFG) .

References

1 Beck J ; Erdeljan H Liquid conservation of root crops . Ag Eng’92 Uppsala , 1 – 4 June , 1992 , 412 – 413

2 Erdeljan H Verfahrenstechnische Untersuchungen zur Flu ̈ ssigkonservierung von Beta-Ru ̈ ben fu ̈ r die Schweine- mast . (Process engineering investigations on liquid conservation of root crops for fattening pigs) Ph . D . Thesis , Hohenheim , 1994

3 Beck J ; Deininger A ; Jungbluth T ; Tu ̈ rk M ; Ho ̈ rnig G Mechanized feeding of ensiled liquid beet mash to dairy cows . Journal of Agricultural Engineering Re- search (1966) 63 (1) : 45 – 52

4 Deininger A Flu ̈ ssig konservierte Beta – Ru ̈ ben in der Rinderfu ̈ tterung – Verfahrenstechniken und Leistungs- fa ̈ higkeit . (Liquid perservated beta beets for dairy cow feeding—process engineering and ef ficiency) Ph . D . Thesis , Hohenheim , 1995

5 Tu ̈ rk M Beitrag zum Berechnen horizontaler Rohrleit- ungssysteme fu ̈ r konzentrierte flie ß fa ̈ hige Hackfrucht-

futtermischungen unter besonderer Beru ̈ cksichtigung des Zuckerru ̈ beneinsatzes . (Calculations of horizontal pipe systems for concentrated fluid flow feed mixtures with sugar beets) Ph . D . Thesis , Rostock , 1975

6 Eck B Technische Stro ̈ mungslehre . (Technical fluid flow) Berlin , Heidelberg , New York : Springer , 1966

7 Skelland A H P Non-Newtonian Flow and Heat Trans- fer . New York , London , Sydney : John Wiley , 1967

8 Tu ̈ rk M ; Ecksta ̈ dt H Berechnung der Reibungsverluste bei turbulenter Rohrstro ̈ mung nicht-Newtonscher or- ganischer Suspensionen . (Pressure drop calculation for turbulent pipe-line flow of non-Newtonian organic suspensions) International Conference on Hydromech- anisation 8 , paper 32 , September 21 – 23 , 1993 , Magde- burg , Germany

9 Tu ̈ rk M ; Schmidt H ; Da ̈ hre D Rotationsviskosimeter fu ̈ r landwirtschaftliche fluide Fo ̈ rdermedien . (Rotational- type viscometers for agricultural suspensions . ) Agrar- technik 1987 , 37 (12) : 568 – 570

1 0 Da ̈ hre D ; Tu ̈ rk M Methode zur Bestimmung absoluter Flie ß kurven nichtlinear – plastischer Medien mit Rota- tionsviskosimetern (Method for determining absolute flow curves of nonlinear-plastic media with rotational- type viscometers) . Chemische Technik 1987 , 39 (11) : 477 – 479

1 1 Tu ̈ rk M Gu ̈ llefo ̈ rderung in Rohrleitungen . Druckver- lustberechung zur Rohrleitungsdimensionierung . (Li- quid manure flow in pipelines . Pressure drop calculation for pipe dimensioning . ) Landtechnik 1994 , 49 (10) : 358 – 359

Documents

Flow Characteristics of Mashed Beet