Computational Flashcards
11. MemSep Components a and b of a gaseous mixture are separated using a membrane t = 2.4 x 10^-3 cm. The pressure on the feed and permeate sides are 58 cm Hg and 21 cm Hg, respectively. The flow rate is 6 x 10^3 cm^3/second and the feed compositions are 60% (mole). The desired reject composition is 46% (mole) the permeability of a and b are 50 x 10^-10 cm/second and 10 x 10^-10 cm/second respectively. Calculate for the membrane area A. 3.62 x 10^ 8 cm^2 B. 7.23 x 10^7 cm^2 C. 4.89 x 10^8 cm^2 D. 9.78 x 10^7 cm^2
D
22.3 ChE Thermo
consider a steam turbine that has an inlet and outlet conditions of 8.6 MPa at 500 C (H=3392 kJ/kg, S=6.686 kJ/kg-K) and 10kPa (vapor: H=2585 kJ/kg, S=8.151 kJ/kg-K; liquid: H=192 kJ/kg, S=0.649 kJ/kg-K), respectively. if the rated capacity of the turbine is 56400 kW at 75% efficiency calculate the following questions:
what is the quality after isentropic expansion
A. 0.61 B. 0.73 C. 0.80 D. 0.91
what is the quality after expansion
A. 0.65 B. 0.74 C. 0.83 D. 0.94
what is the mass flow rate of the steam kg per second A. 48 B. 59 C. 66 D. 74
C
D
B
22.1 ChE Thermo
consider a 1.0 mol of van der waals gas (a = 0.015 Pa-m^6/mol^2; b = 3.93x10^-6 m^3/mol) that is expanded isothermally at 298 K and reversibly from 3 L to 10 L.
(π_T=T(δP/δT)_V - P)
what is the value of ΔU (J)
A. 0 B. 3.5 C. -3.5 D. 2.5
what is the value of W (J)
A. -2982.9 B. 2982.9 C. -2981.7 D. 2981.7
what is the value of Q (J)
A. -2982.9 B. 2981.7 C. 2985.2 D. -2978.2
B
C
C
22.2 ChE Thermo what is the change in entropy associated with the phase change kJ/K if a kilogram of ice at -15 degrees celsius was melted to ambient temperature? A. 0.5 B. 0.9 C. 1.3 D. 1.7
D
13. BioChE an amount of 1 gram of bacteria was found to utilize a substrate at a rate of 40 grams/day when the substrate concentration is high. another experiment found that the same mass of bacteria can utilize the substrate at a rate of 20 grams per day when the substrate concentration is 28 mg/ liter. what is the rate of consumption in grams/ day by 2 grams of bacteria if the substrate concentration is set at 10 mg/ liter A. 10.53 B. 20 C. 21.05 D. 14.21
C
29.1 Leaching
Ground roasted coffee contains 8% soluble solids, 2% water and 90% inert insoluble solids in order to obtain an extract with high soluble solids content without having to a concentrate it for spray drying, a countercurrent extraction process is to be used to prepare the extract. it is desired that the final extract contains 0.15 kg soluble per kg water and that the soluble of the spent coffee grounds not to exceed 0.008 kg per kg dry inert solids. the coffee grounds carry 1 kg water per kg of soluble-free inert solids and this quantity is constant with the solute concentration in the extract.
- the amount of final extract is approximately equal to
- the concentration of solution adhering to the extracted solid is approximately equal to
- the water-coffee ratio to be used in the extraction is
- the number of extraction stages needed for this process is
- 55.81 kg
- 0.008
- 1.37
- 6
29.2 Leaching
Calcium carbonate precipitate can be produced by the reaction of an aqueous solution of sodium carbonate and calcium oxide the by-product is aqueous sodium hydroxide. following decantation the slurry leaving the precipitation tank is 5 weight percent calcium carbonate 0.1 weight percent sodium hydroxide and balance water. 100,000 pounds per hour of the slurry is fed to a two-stage continuous countercurrent washing system to be washed to 20,000 pounds per hour of freshwater. the underflow from each thickener will contain 20 weight percent solids.
1. the amount of extract (pounds per hour) is approximately equal to
2. the amount of sodium hydroxide (pounds per hour) in final extract is approximately equal to
3. the amount of sodium hydroxide pounds( per hour) in final underflow is approximately equal to
4. the percent recovery of sodium hydroxide in the extract is approximately equal to
- 95000
- 90.48
- 9.52
- 90.48
30.1 Gas abs
Suppose a gas absorption tower needs to remove 99% of N2O4 in air. the packing will be 16-mm Pall rings. the gas enters at the rate of 1 lbm/s and contains 1 weight % N2O4 and 99% air at 300 kelvin. the absorbent consists of water entering at 0.2 lbm/s. the N2O4 reacts readily with water. assume Kya = 100 lbm N2O4 / h-ft^2-Δy and the capacity at the flood point is 1000 lbm gas/h-ft^2. The units of y are lbm N2O4/lbm air
1. suppose 75% of the flood point is used as operating gas velocity calculate the diameter of the column
2. calculate the height of a theoretical stage (Hog)
3. since N2O4 reacts with water readily assume that all interface concentration is 0 and calculate the number of theoretical stages (Nog)
4. what is the height of the column
5. the total weight of the Pall rings is ____ lbs
- 2.47 ft
- 7.4 ft
- 4.61
- 34.1 ft
- 5204 lbs
30.2 Gas abs the interfacial concentration y_i in a gas absorber corresponding to y = 0.05 mole fraction is \_\_\_\_\_ mole fraction. the slope of the operating line is 1.3 with the mole ratios Y1 = 0.08, Y2 = 0.03 and X2 = 0 the equation of the equilibrium curve is y = 0.8 x, the MTC's are kxa = 60 and kya = 15 lbmole/hr-ft^3-mole fraction concentration difference A. 0.2 B. 0.064 C. 0.046 D. none of these
A.
26.1 Flotation
600 tons of ore is being treated daily. An ore contains 8% PbS and 92% SiO2. laboratory experiments show that L/S=4 and the contact time is 10 minutes in the rougher, and L/S = 3 for 19 minutes in the scavenger. concentrate: PbS = 85%, SiO2 = 15%; rougher tailings PbS = 4%, SiO2 = 96%; scavenger concentrate PbS = 7%, SiO2 = 93%; final tailings PbS =2% SiO2 = 98%. ρ_PbS=7.5 g/cm^3; ρ_SiO2 = 2.65 g/cm^3.
1. what is the required rougher volume?
2. what is the required scavenger volume?
3. what is the yield of lead sulfide in the concentrate?
- 1 ft^3
- 2 ft^3
- 8%
26.2 Flotation ground lead ore is to be concentrated by a single flotation process using 1.5 oz of reagent per ton of ore to feed concentrate and tailings have the following composition by weight on a dry basis Feed: 30% PbS, 70% Balance Concentrate: 90 %, 10 % Balance Tailings: 0.9% PbS, 99.1% Balance
water is fed to the cell at the rate of 1,000 gallons per ton of wet concentrate with 99% of the water leaving with the tailings and 1% with the concentrate.
1. mass of wet concentrate produced when 10 tons of ore are fed to the cell for 24 hours is
A. 3.4
B. 4.3
C. 14.23
D. 4.7
2. total water required in pounds per hour is A. 1150 B. 1200 C. 1185 D. 1285.8
A
C
16.1 Heat Transfer
a thick walled tube of stainless steel having a k = 21.63 W/mK with dimensions of 0.0254 m ID and 0.0508 m OD is covered with a 0.0254-m layer of asbestos insulation, k = 0.2423 W/m-K. the inside wall temperature of the pipe is 811 k and the outside surface of the installation is at 310.8 K
1. For a 0.305m length of pipe calculate the heat loss
A. 132 Btu/hr
B. 213 Btu/hr
C. 1132 Btu/hr
D. 2311Btu/hr
2. what is the temperature of the interface between the metal and the insulation? A. 805.5 K B. 800.5 K C. 80.5 °C D. 58.5 °C
C
A
16.2 Heat transfer
an electric current of 200 A is passed through a stainless steel wire having a radius of 0.001268 m. the wire is 0.91 m long and has a resistance of 0.126 Ω. outer surface temperature is held at 422.1 Κ. average thermal conductivity is 22.5 watts per meter- kelvin.
1. calculate the volumetric heat of generation in GW/m^3
A. 1.1
B. 2.2
C. 3.3
D. 4.4
2. calculate the center temperature (K) A. 410 B. 420 C. 430 D. 440
A
D
16.3 Heat transfer a layer of pulverized cork 6-in thick is used as a layer of thermal insulation in a flat wall. the temperature of the cold side of the cork is 40 degrees fahrenheit and that of the warm side is 180 degrees fahrenheit. the thermal conductivity of the cork at 32 °F is 0.021 Btu/ft-hr-°F and that at 200 °F is 032. if the rate of heat flow through the wall is 182 BTU/hr, what is the area of the wall? A. 20 ft^2 B. 25 ft^2 C. 30 ft^2 D. 35 ft^2
B
16.7 Heat transfer A small oxidized horizontal metal tube with an OD of 0.0254 m and being 0.61 m long with a surface temperature at 588 K is in a very large furnace enclosure with fire brick walls and the surrounding air at 1088 K. Calculate the heat transfer to the tube by radiation. The emissivity of the metal tube is 0.60 at 1088 K and 0.46 at 588 K? A. 102 W B. 507 W C. 2130 W D. 7270 W
C
16.4 Heat transfer Air at 206.8 kPa and an average temperature of 477.6 K is being heated as it flows through a tube of 25.4 mm inside diameter at a velocity of 7.62 m/s. The heating medium is steam condensing on the outside of the tube, whose temperature is 488.7 K. 1. The flow inside the tube is A. Laminar B. Transition C. Turbulent D. does not flow
2. What is the heat transfer coefficient in W/m^2-K A. 44.5 B. 63.2 C. 86.7 D. 99.1
3. Calculate the heat flux in W/m^2 A. 400 B. 500 C. 600 D. 700
C
B
D
16.5 Heat transfer
A heavy hydrocarbon oil (Cp = 2.30 kJ/kg-K) is being cooled in a countercurrent heat exhanger from 371.9 K to 349.7 K and flow inside the tube at a rate of 3630 kg/h. A flow of 1450 kg water/hr enter at 288.6 K for cooling and flows outside the tube. The overall heat transfer area is Ui = 340 W/m^2-K.
1. What is the log mean temperature difference?
A. 319 K
B. 182 K
C. 74.5 K
D. 56.9 K
2. What is the heat transfer area in m^2? A. 1.37 B. 2.66 C. 3.12 D. 3.48
3. If the flow is parallel, what is the water outlet temperature? A. 319 K B. 323 K C. 342 K D. 376 K
D
B
A
16.6 Heat transfer
Water at an average of 70 degF is flowing in a 2-inch steel pipe, sch 40. Steam at 220 degF, is condensing on the outside of the pipe. The convective coefficient for the water inside the pipe is h = 500 Btu/hr-ft^2-F and the condensing steam coefficient on the outside is h=1500.
1. What is the heat loss per unit length of 1 ft of pipe using resistances?
- What is the overall Ui based on the inside area in Btu/hr-ft^2-F?
- What is the Uo?
26700 Btu/hr
330
290 Btu/hr-ft^2-F
16.8 Heat Transfer assuming reynolds analogy applies, estimate the heat transfer coefficient in BTU/hr-ft^2-°F, for water flowing inside a 2.0 in ID smooth horizontal straight pipe at a velocity of 4 fps and an average temperature of 78 °F. A. 1790 B. 2000 C. 2910 D. 2240
D
44.1 Adsorption Concentration(kg/m^3)/q(kg/kg) 0.0061/0.15 0.0055/0.122 0.0038/0.094 0.0024/0.059 0.0011/0.045 1. which of the following model best describes the experimental data? A. henry B. langmuir C. freundlich D. BET
2. A 1.0 m^3 solution has a concentration of 0.21 grams/L. Fresh 1.4 kg adsorbent is added to the solution and mixture thoroughly. using the previous model what percent of the adsorbate is removed A. 67 B. 77 C. 87 D. 97
D
44.2 Adsorption Consider a 2.4 m diameter column with a height if 6 m was tested for its adsorptive capacity. A 0.13 m^3/s wastewater, that contains 12% of a certain pollutant, was reduced to an allowable value of virtually zero. the adsorption data are as follows: time(h)/outlet conc (%) 0/0 4/0 4.3/0.5 4.6/1.1 4.9/2.6 5.2/4.9 5.5/8.6 5.8/10.2 6.1/11.3 6.4/11.8 6.7/11.9 1. What is the breakthrough time (h)? 2. what is the height of the bed (m) used up until allowable concentration? 3. what is the superficial velocity of the wastewater (m/s)?
- 072
- 41
- 03
44.3 Adsorption In bleaching or removal of coloring substances of material such as coconut oil or sugar, decolorizing agents such as activated carbon is used. bleaching can be carried out in a single pass or multipass or other methods. if 80% of the color is removed in a single stage decolorization with 4% activated carbon, the activated carbon that will be needed to remove the same amount of color in a two-stage countercurrent equalization if n=2 A. 0.025 B. 0.0223 C. 0.03 D. 0.04
B
