No. 1, 1998 - Tribology in Industry

---
ro ^'
K- rh:tt -, J (6)
i)
wlrere r* : (Lp.R)(2.1,f1 is the wall shear srress,
Wrr=Q'(n'R2;-1 is the average velocity (e:flow rate),
ro=2'L'to'(Lp)-/ and:
A - t.2n .(3n t 1)-1 .tt -'ff *
- 2n.(2n + i)-r .,o. R 1.11 , "\
(7)
Fig 3. Gel flotu in pipe velocity distibution
With relations i5), (6) and (7), k and n paramerers can
be determined. But, is necessary to have the values for
R, r, T, A,p, L, W,r, etnd tr,r.
given the velocity distnbution in the form:
!1
| ,._lln r \ .
4y' = lAtt.(2.k.L)
'
l' (/" ,o), ,tr G)
In relations (3) and @): Lp is the pressure, L the length,
r the radius and ro=).1.1o.(Lp[] is the radius of central
zone which has a constant velocify, w, (fig.3).
In (3) are presented ihe equations for shear rate and k
parameter, in the fcrllowing form:
J-(rr+ I).n I.(.ll_rrr)-t.14/,,,.A-,
Table L Erpeimettal
R,
m
x1 O-3
values
(s)
3. EXPERIMENTAL RESULTS
The capillary tube viscometer with a poiseuille flow
(ASTM D 1092) rvere used for measurements. For test,
there were used two gels with characteristics presented
(table 1) in the secrion I of this paper. The results of tests,
at 300K are shown in talrle 1.
The yield stress is calculated using the equation:
r,,= (&.R).(2.L) I 6)
The pressure (&r) in the reservoir of the capillary tube
vrscorneter was lncreased very slowly and the start_up
Ap, MPa I r*, kpa ro, m.10-3
Sampie no.
1.890 8go, r5r.z 151.2 iLo.o044
i
94 i 6.84 i 2.00
1l8s __9_18 oo113 i 38 , _r!__l*
O e4s ,
2.eo
-1_+ I
75.6 I o.or zs i ts I rz.oo i +.oo
s6B7 I
0600 i _!!_c_ i opye
OSjs ) 41.2 0.0600
1 .890 t 5t .2 r O.OO71
ires-- e+s -oi1Bl
0 945 75.6 ; 0.0285 1500 I
500 j _rjilt
312s i 0.302
0760 1 608 | o.oaqt zJl
0 600 48.0 o
-
}ZOT 472
- L-
o 51s I at .z i o.oe6o 746
1980 1s:r .2 i o.Or a
94.8 I o.ozso
u. t zv 0.0ggg
41.2 0.1540
4/ .0U 16.90 29375 10562 '"Y
, _'u' " L
z4oo I astso i laoool;*A_
'
I
n ,
I 0.0613
tv.vvrv i 0.05'1
Tiibologt itr indrctry,, Volume 20, No. l, 199g.
t7