Download B49CD combined Tutorial final answers

TOPIC 1-EVAPORATION TUTORIAL FINAL ANSWERS
Q1 30.9 C, 249 kg/hr
Q2 333 W/m2.K, 0.87 kg/kg steam
Q3 17769 kg/hr, 0.925 kg/kg steam 56.6 m2, 18814 kg/hr 0.87 kg/kg steam 60.0 m2,
16354 kg/hr 1.01 kg/kg steam 52.1 m2.
Q4 vapour = 4.8 kg/s
Q5 a, U = 1145 W/m2 K , Economy = 0.83 kg/kg steam
b, 971 kg/hr, 10.3 % w/w solids
Q6 U1 = 373 W/m2 K, U2 = 301 W/m2 K, Economy = 1.52 kg/kg steam.
Q7 Using Method 1 from the lecture slides: 2.41 kg/s, A1 = 71.8 m2, A2 = 90.1 m2, A3
= 92.9 m2, average A = 84.9 m2. Exact values will depend on how delta T1 was
altered to allow for cold feed. Method 2 is shown in the recorded tutorial session.
TOPIC 2- DRYING TUTORIAL FINAL ANSWERS
Q1 7.89 hr
Q2 13.5 hr
Q3 7.92 hr note moisture content does not go as low as the critical moisture content,
there is no falling rate period. Student guide Eqn 2.15 can be used replacing wc with
w2. Using wc will give an answer for the WHOLE of the critical rate period which is
inappropriate as moisture does not go down to the critical value.
Q4 0.00235 kg/kg dry basis.
Q5 3.25 hr
Q6 approx. 2.4 kg/m2 hr and 0.155 kg H2O/kg dry solid, depending on how you read
the graph.
Q7 0.0696 kg/s dry solids, 0.0240 kg/kg dry air
Q8 43.4 C, 0.640 kg/s, 1.28 m, 7.69 m
Q9 1.93 and 7.88 m. You know the actual temperatures in and out for the solid and
the temperature in for the air so do not need to make any assumptions when
calculating the air outlet temperature.
Q10 and 11 just leave unless you are very keen.
TOPIC 3-PARTICLE TECHNOLOGY TUTORIAL FINAL ANSWERS.
BEWARE when using the charts in C & R volume 2, C & R's dimensionless groups
are not always the same as those given in the notes, having half the value. If in
doubt look closely at the dimensionless groups given in C & R volume 2 or just use
the 'computer formula'.
Q1 Assume cyclist is a ~ 0.5 m sphere - this is a rather dubious assumption but is
roughly the correct order of magnitude, calc Re, find CD, Force = 0.508 N
Assume car is a ~ 2.0 m sphere - another slightly dubious assumption, force = 376 N
Q2 Find Re from a chart of CDRe0^2, U0 = 0.15 m/s
Q3 Similar to Q2, assume CD = 0.44 (fully developed laminar flow), calculate
CDRe0^2, calculate U0 using CD = 0.44, check Re is in the correct range, U0 = 11.1
m/s, t = 9 s.
Q4 use Haywood's method. U0 = 0.12 m/s
Q5 Calculate cut off sizes for each material using CD/Re and chart, from the particle
distributions you will then know the split for each material. the elutriated stream
contains 13.3 % galena and the stream leaving the bottom of the equipment contains
34.2 % galena. Note if the Reynolds number of the largest particles were slightly
lower, you could use Stokes Law instead.
Q6 Assume fully developed laminar flow 22.2 s
Q7 Use chart in C & R vol 2 to find Re, d = 3 mm. Voidage is < 0.98, particles are
well below 100 mm so are fine not coarse, therefore use eqn 3.27 and eqn 3.29 find
Ua , Ua = 0.208 m/s
Q8 0.0295 m/s
Q9 Use Darcy's eqn, B = 7.7 x 10^-13 m^3, Kozeny eqn, assume K = 5, S = 1.19 x
10^-5 m^2/m^3