Fluidization of a Sand Bed Filter. To clean a sand bed filter it is fluidized at minimum conditions using water at 24"C. The round sand particles have a density of 2550 kglm3 and an average size of 0.40 mm. The sand has the properties given in Table 3.1-2. (a) The bed diameter is 0.40 m and the desired height of the bed at these minimum fluidizing conditions is 1.75 m. Calculate the amount of solids needed. (b) Calculate the pressure drop at these conditions and the minimum velocity for fluidization. (c) Using 4.0 times the minimum velocity, estimate the porosity and height of the expanded bed.

21. A plate and frame filter press is used to filter a compressible sludge (S = 0.45) at 50 psia for 2 hours. Washing is done at 30 psi with wash water equal to 10% of the filtrate volume collected. The washing time is a. 100 min b. 127 min c. 85 min d. 205 min

Explain the difference (in concept or definition) between boundary layer thickness and thermal boundary layer thickness?

2. A 1 L, 100 g (dry weight) sample is removed from a continuous crystallizer which is operated with a residence time of 1000 s. The following particle size distribution is obtained for the sample: i) Size range (um) Mass (g) 200- 300- 400 500 600-700- 800- 300 400 500 600 700 800 900 0- 100- 100 200 2.5 26.0 30.0 21.0 12.0 6.0 2.0 0.5 0.0 Microscopy based on the sieve fractions has found that a volumetric shape correction factor, ky, of 0.52, for the crystal population and the crystal density has been found to be 2000 kg/m³ Determine whether the MSMPR model describes the system. If it does so, then determine the growth and nucleation rates for this system; if it does not, suggest why reasons that may cause deviation of this CSTR type crystallizer from the MSMPR model.

Provide an example of a mass transfer problem in which both diffusion and convection are important.

b) A complete drying experiment for two different materials (sand and minced meat) was conducted in the laboratory. The results of drying rate for both materials are as shown in Figure 3. Compare and explain the drying rate behavior for sand and minced meat. Drying rate Sand Minced meat Drying time Figure 3 Relation between drying rate and drying time

Q13. The wear resistance of a steel gear is to be improved by hardening its surface. This is to be accomplished by increasing the carbon content within an outer surface layer as a result of carbon diffusion into the steel; the carbon is to be supplied from an external carbon-rich gaseous atmosphere at an elevated and constant temperature. The initial carbon content of the steel is 0.20 wt%, whereas the surface concentration is to be maintained at 1.00 wt%. For this treatment to be effective, a carbon content of 0.60 wt% must be established at a position 0.75 mm below the surface. Specify an appropriate heat treatment in terms of temperature and time for temperatures between 900 °C and 1050 °C (you may select any 3 temperatures). For the diffusion of carbon in steel, Do = 2.3 x 10 m/s, Q = 148 kJ/mol. (The error function values are given below) erf(2) erf(z) 0.55 0.60 1.3 1.4 0.5633 0.9340 0.025 0.0282 0.6039 0.9523 0.05 0.0564 0.65 0.6420 1.5 0.9661 0.10 0.1125 0.70 0.6778 1.6 0.9763…

Produce a plot (graph) showing the shape of the PVT-surface for the ideal gas equation.

Most organisms' DNA polymerases denature at  _____ temperatures needed to break DNA strands.   a. low   b. medium   c. high   d. any

which of these statements are true or false