Prediction of batch heat transfer coefficients for pseudoplastic fluids ...
Prediction of batch heat transfer coefficients for pseudoplastic fluids ... Prediction of batch heat transfer coefficients for pseudoplastic fluids ...
18 suddenly seemed to become more viscous when a large diameter bob 'i;'JaS used at high speeds. The problem was easily eliminated by using a smaller diameter bob, thus greatly reducing the linear velocity of the bob at the expense of a small increase in clearance. T.emJ2erature effects.. In very viscous fluids the heat generated by fluid friction is enough to cause a temperature rise. The un1tJary investigator may then mistakenly report pseudoplasticity or thixotropy due to the decrease in apparent viscosity which in actuality is caused by the increase in temperature. McKelvey (114) reports that the heat generation per unit volume is the product of the shear stress, shear rate, Heat generation = "~i J (2-16 and convers ion factor to heat units. WeI tmann (206) has derived a complex equation giving the temperature variation with radius caused by viscous heating. Heat generation is not a problem for lOH viSCOSity materials and good temperature control. Time dependency. Thixotropic fluids may best be measured in a rotational viscometer. The shearing stress is determined for various times of shear at a constant shear rate. The apparent viscosity is plotted versus the natural logarithm of the time of shear and the slope is called the I1 coefficient
19 of' thixotropic breakdown l'Ji th time!l ( 79). If' the slope is zero the f'luid is not time dependent.
- Page 1 and 2: Copyright Warning & Restrictions Th
- Page 3 and 4: PREDICTION OF BATCH HEAT TRANSFER C
- Page 5 and 6: while the latter has five to seven
- Page 7 and 8: ACKNOWLEDGEMENTS The auther ex~ress
- Page 9 and 10: Chapter 1: Chapter 2: Introducticm
- Page 11 and 12: LIST OF FIGURES page 2-1 FlGW Behav
- Page 13 and 14: CHAPTER I INTRODUCTION BATCH HEAT T
- Page 15 and 16: 3 as pseudoplasticso Pseudoplastic
- Page 17 and 18: 5 ~n addition to studying the effec
- Page 19 and 20: 7 A B SLOPE = /'n- .( 10 ~y FIG 2-1
- Page 21 and 22: 15.5, 183, 185).. Most of their eff
- Page 23 and 24: va:ry withl. the slaear I'Rte.. 11.
- Page 25 and 26: 13 RHEOLOGIC_~ INVESTIGATION OFPO~~
- Page 27 and 28: IS In(s) (2-8 (2-9 where Re is the
- Page 29: '7 ft~ easier method of calibrating
- Page 33 and 34: 21 complicated by a variable viscos
- Page 35 and 36: 2J Schultz-GrQnow (174) used a dime
- Page 37 and 38: 2S The results shm-red that equatio
- Page 39 and 40: Su.bstituti011 of equati 2-22 gives
- Page 41 and 42: 29 In both Newtonian and non-Newton
- Page 43 and 44: 31 for viscous pseudoplas tics at 1
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- Page 47 and 48: JS Thermometers or thermocouples ar
- Page 49 and 50: .37 2: a in in heat cQ@tent of the
- Page 51 and 52: J9 cooling mediu..:m side, the heat
- Page 53 and 54: 41 ports a value of 3/4-.. He then
- Page 55 and 56: 43 find the effects of one or two o
- Page 57 and 58: 45 The group to the left of the equ
- Page 59 and 60: 47 the highest heat tra...nsfer coe
- Page 61 and 62: 49 A pitched blade turbine gave coe
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- Page 65 and 66: 5J evaluated at the wall temperatur
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- Page 69 and 70: CHAPTER .2 DEVELOPMENT OF CORRELATI
- Page 71 and 72: momentum" mass" and energy may be ~
- Page 73 and 74: 61 Vr;> Jt.- ,,"Ii'\... ..", ::: (V
- Page 75 and 76: 63 Substitution of these dimensionl
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18<br />
suddenly seemed to become more viscous when a large diameter<br />
bob 'i;'JaS used at high speeds. The problem was easily eliminated<br />
by using a smaller diameter bob, thus greatly reducing<br />
the linear velocity <strong>of</strong> the bob at the expense <strong>of</strong> a small<br />
increase in clearance.<br />
T.emJ2erature effects..<br />
In very viscous <strong>fluids</strong> the <strong>heat</strong><br />
generated by fluid friction is enough to cause a temperature<br />
rise. The un1tJary investigator may then mistakenly report<br />
<strong>pseudoplastic</strong>ity or thixotropy due to the decrease in<br />
apparent viscosity which in actuality is caused by the increase<br />
in temperature.<br />
McKelvey (114) reports that the <strong>heat</strong><br />
generation per unit volume is the product <strong>of</strong> the shear stress,<br />
shear rate,<br />
Heat generation = "~i J (2-16<br />
and convers ion factor to <strong>heat</strong> units. WeI tmann (206) has<br />
derived a complex equation giving the temperature variation<br />
with radius caused by viscous <strong>heat</strong>ing. Heat generation is<br />
not a problem <strong>for</strong> lOH viSCOSity materials and good temperature<br />
control.<br />
Time dependency.<br />
Thixotropic <strong>fluids</strong> may best be measured<br />
in a rotational viscometer.<br />
The shearing stress is determined<br />
<strong>for</strong> various times <strong>of</strong> shear at a constant shear rate. The<br />
apparent viscosity is plotted versus the natural logarithm<br />
<strong>of</strong> the time <strong>of</strong> shear and the slope is called the I1 coefficient