Chemical Engineering

A burst of 1 x 10^9 neutrons from a pulsed accelerator is introduced into a subcritical assembly consisting of an array of natural uranium rods in water. The system has a multiplication factor of 0.968 . Approximately 80% of the incident neutrons are absorbed in uranium. (a) How many first-generation fissions do the neutrons produce in the assembly?

A burst of 1 x 10^9 neutrons from a pulsed accelerator is introduced into a subcritical assembly consisting of an array of natural uranium rods in water. The system has a multiplication factor of 0.968 . Approximately 80% of the incident neutrons are absorbed in uranium. (a) How many first-generation fissions do the neutrons produce …

A burst of 1 x 10^9 neutrons from a pulsed accelerator is introduced into a subcritical assembly consisting of an array of natural uranium rods in water. The system has a multiplication factor of 0.968 . Approximately 80% of the incident neutrons are absorbed in uranium. (a) How many first-generation fissions do the neutrons produce in the assembly? Read More »

Problem3 The gas-phase reaction 4A→ 3B + 2C occurs via the following sequence of elementary steps. Y and Z are reactive intermediates. a) Obtain an expression for the reaction rate, r, in terms of the reaction rate for step 3, r3. Note that the elementary steps written may need to occur multiple times to give the overall reaction stoichiometry b) Using your answer from part A, obtain an expression for the reaction rate, r,in terms of rate constants and concentrations of reactants and products assuming only PSSH on the intermediates. c) Experimentally, at some conditions, the reaction rate exhibits the following dependence on the concentration of A and B (A)2 What approximations are required in the rate expression obtained in part B in order to explain the concentration dependence on this rate? d) For the general case, simplify the rate expression obtained in part IB assuming that: (i) Step 1 is irreversible ii) Step 1 is quasi-equilibrated

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1) Water at 10°C flows from a large reservoir to a smaller one through a 5- cmdiameter cast iron piping system, as shown in Fig. 8-48. Determine the elevation z1 for a flow rate of 6 L/s. Sharp-edged entrance, KL 0. 5 Standard elbow, flanged, KL-0.3 D-5 cm G ate valve, fully open K-0.2 9m Control volume boundary 80m -Exit, KL = 1.06

EXPERT ANSWER Given: Diameter of pipe, D=5 cm=0.05 m Flowrate of water, Q=6 L/s=0.006 m3/s Total length of pipe, L=Horizontal length+Vertical length= 80m+9m=89 m Elevation at point 2, z2 =4 m Loss coefficient for sharp edged entrance, KL, entrance=0.5 Loss coefficient for standard flanged elbow, KL, elbow =0.3 Loss coefficient for gate valve (fully open), KL, valve =0.2 Loss …

1) Water at 10°C flows from a large reservoir to a smaller one through a 5- cmdiameter cast iron piping system, as shown in Fig. 8-48. Determine the elevation z1 for a flow rate of 6 L/s. Sharp-edged entrance, KL 0. 5 Standard elbow, flanged, KL-0.3 D-5 cm G ate valve, fully open K-0.2 9m Control volume boundary 80m -Exit, KL = 1.06 Read More »

4.- What is minimum T? What values are typically used in design? 5.- What is the heat content diagram method? How different is it from the crease point method?

4.- What is minimum change in T? What values are typically used in design?5.- What is the heat content diagram method? How different is it from the crease point method? EXPERT ANSWER ANSWER : (4) Delta T min is the minimum permissible temperature difference between hot and cold streams entering and exiting an individual heat exchanger …

4.- What is minimum T? What values are typically used in design? 5.- What is the heat content diagram method? How different is it from the crease point method? Read More »

Question 3. Consider a porous catalyst with a cylindrical geometry having an inner radius ri, outer radius r2and an axial length L, embedded in an impermeable substrate. Gas A is maintained at a constant concentration CA in the open area at the center and diffuses from the interior of the cylinder toward the outer wall of the cylinder. While doing so, it reacts with the catalyst to produce gas B: A-B This reaction is zero-order in the concentration of A, and proceeds at a constant rate per unit volume: rA- k (mol A)(m3 s)1 The effective diffusion coefficient of A is Deff. The system is at steady-state. mpermeable Substrate Catalyst a) Use a shell balance to derive the differential equation that describes how the concentration b) c) d) of A changes in the radial direction. Clearly state all assumptions in your solution. What boundary conditions will you use to solve this diff. eq.? Solve the diff. eq. to find the concentration of A as a function of r. Derive the effectiveness factor for this system when the concentration of A is non-zero at all positions. (copying an equation from notes is worth zero points)

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3. (35 points) Consider a gas-phase reaction that occurs via the following sequence of elementary steps (l; are reactive intermediates): ki = 15-7 A-321 B+1, ** 12 212 ** C +13 213.D k2 = 12 dm² mol st kz = 30 dm’ mot’s k4 = 90 dm mot’ 57 (a) Setting up the problem: (i) Write the stoichiometric numbers (G) for each elementary step, if I molecule of D is formed in each reaction event (e.g., in the overall stoichiometric reaction). (ii) Write out the overall stoichiometric reaction. (iii) Write expressions for the overall reaction rate, r, in terms of the rates of each elementary step, ri. (iv)Write expressions for the overall reaction rate, r, in terms of the rates of formation of each species, r;. (b) Derive the rate expression for the rate of production of D, rd, in terms of rate constants and concentrations of reactants and products by applying the pseudo steady-state hypothesis (PSSH) for all reactive intermediates. (c) Based on the rate law determined in part (b), determine the steady-state effluent concentration of A. C. for a CSTR (10 dm) with inlet volumetric flowrate 50 dm min and inlet concentrations CA=50 mol dm3 and CBo=150 mol dm. (Hint: this is a gas-phase reaction. Is the overall stoichiometric reaction equimolar, and if not, what is the value of £?)

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Q2) Ammonia (A) diffuses through a stagnant layer of air (B), 10 cm thickness, at 25°C and 10 atm total pressure. The partial pressures of NH, on the two sides of the air layer are P0.9 atm and PAL -0.1 atm respectively. Airis non diffusing, Calculate: (a) The molar flux of NH3 (b) The velocities of the individual components with respect to a stationary observer (c) The molar and the mass average velocities of the components and (a) The molar flux of NH, with respect to an observer moving with the mass average velocity GIVEN DATA: DAB -0.214 cm

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Q5)) A single acting reciprocating pump has cylinder diameter of 200 mm and stroke length 300 m. The suction pipe is 100 mm diameter with 8 m long. The punp draws water 4 m below the cylinder axis. If the speed of the pump is 30 rpm. Find the pressure head on the piston at the beginning, middle and end of the suction stroke Notes: 1) The friction factor =0.01 and the atmospheric pressure head is 10.3 m of water. 2) The general pistion head equation is given by: Hpiston=Hatm+Zz-ha-hus 25M Q5)) A single acting reciprocating pump has cylinder diameter of 200 mm and stroke length 300 m. The suction pipe is 100 mm diameter with 8 m long. The punp draws water 4 m below the cylinder axis. If the speed of the pump is 30 rpm. Find the pressure head on the piston at the beginning, middle and end of the suction stroke Notes: 1) The friction factor =0.01 and the atmospheric pressure head is 10.3 m of water. 2) The general pistion head equation is given by: Hpiston=Hatm+Zz-ha-hus 25M

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