The flat iceberg drifts over the ocean, as it is driven by the wind that blow over the top. The iceberg may be modeled as a block of frozen fresh water at 0 oC. The temperature of surrounding sea water is 10 oC, and the relative velocity between it and iceberg is 10 cm/s. The length of iceberg in the direction of drift is L=100 m. The relative motion between the sea water and the flat bottom of the iceberg produce a boundary layer of length L. The 10 oC temperature difference across this boundary layer drives a certain heat flux into the bottom surface of the iceberg. This heating effect causes the steady erosion (thinning) of the flat piece of ice. If H(t) is the instantaneous high of the ice slab, calculate the ice melting rate dH/dt average over the swept length of the iceberg.

An isothermal CSTR is used for liquid phase reaction A+B→C+D, -ra=kC_a*C_b   and k=1x10^11 exp⁡((-36900)/2.74T) determine the residence time required for this reaction to achieve 60 % conversion of the limiting reagent and mole fraction of C. The feed to the reactor is 200 mol/min A and 150 mole/min of B with flow rate of 20 l/min. The inlet temperature is 497 K.

For the transfer function in question 4, use the Skogestad’s “Half Rule” method to find an approximate second-order-plus-time-delay model of the form Ke-θs/{(τ1s+1)(τ2s+1)} and determine the values of

a. ________

b. ________

c. ________

Q) Write the problems caused if an uncalibrated machine is used for some analysis?

Discuss why bulk micromachining of silicon could generate high-aspect ratio features (e.g. deep valleys) with well-defined side walls instead of undercutting into the material.

1. Write very briefly about the following:                                                                        

a)  Fick’s second law and its application

b) Different Mass transfer coefficients

c) Raoult’s law and Henry’s law and their applications  

d) Give the j_D correlation for mass transfer in flow parallel to flat plate

e)  Chilton – Colburn analogy

f) Capacity coefficients and their use

g) Marangony effect

2. Explain and derive the Mass transfer flux equation for molecular diffusion in gases for the case of (i) Equimolar counter diffusion and (ii) A is diffusing through stagnant non diffusing B.
3. a) Explain the diffusion through a varying cross sectional area and derive the equation for mass transfer flux.

        4)   a) Explain briefly about the diffusivities in gases

b) Explain briefly about the diffusivities in liquids

1. Explain the diffusivities of electrolytes in liquids              

b) Predict the diffusion coefficients of dilute electrolytes for the following cases:

i) For  KCl at 25 ⁰C, calculate  .

ii) For  KCl at 18.5 ⁰C, calculate  .             

iii) For  CaCl₂ at 25 ⁰C, calculate  . Also predict Di of ion Ca⁺² and of  Cl^-.

Data: λ₊(K⁺) =73.5, λ_-(Cl^-) =76.3, λ₊(Ca²⁺/2) = 59.5

       6)   Explain (a) The two film theory and (b) The penetration theory.                       

      7)   Explain the mass transfer in the laminar boundary layer when the fluid is in laminar flow over a flat plate.

8).Explain the following briefly.

1. Individual and overall mass transfer coefficients.
2. Reynolds analogy.   

A shell-and-tube heat exchanger is to used to heat water (in the tube side) from 30 deg C to 40 deg C at a mass flow rate of 4 kg/s. The fluid used for heating (shell side) is water entering at 90 deg C with a mass flow rate of 2 kg/s. A 1-2 STHE is used and the overall heat transfer coefficient based on the inside area is 1390 W/m2-K. The tubes are 1.875 in diameter (inside) and require an average velocity of 0.375 m/s.

What is the effective (corrected) temperature driving force in deg C?

a. 37
b. 35
c. 42
d. 30

How many tubes are available per pass?

a. 31
b. 20
c. 39
d. 43

What is the required heat transfer area in m2?

a. 4.2
b. 5.7
c. 4.8
d. 5.2

What length of pipe will be required to accomplish the desired heat transfer?

a. 1.12 m
b. 2.12 m
c. 1.79 m
d. 2.5 m

- Air with (μair = 2.27*10-5 pa.s, T = 394.3 K, M.wt of air = 28.97), flows through a packed bed of cylinders having a diameter of 0.03 m, and length the same as the diameter. The bed void fraction is 0.45 and the length of the packed bed is 4 m. The air enters the bed at 1.5 atm abs at the rate of 3.5 kg/m .s based on the empty cross section of the bed. Calculate the pressure drop of air in the bed.

The following data were obtained for the adsorption of n-butane on a porous solid (catalyst).  

If the area occupied by a n-butane molecule is 0.55 nm² at 85 °C, estimate the surface area of the catalyst (in m²/g) assuming Langmuir adsorption isotherm.

What is the purpose of using Hickman still instead of a conventional distillation apparatus in this synthetic experiment? Explain the advantages.

A liquid mixture of benzene and toluene is contained in a closed vessel at 60°C. The only other component in the system is nitrogen gas which is used to pressurize the system to 1 atm total pressure (absolute). The liquid is 70 mole% benzene and 30 mole% toluene, and the N₂ is considered non-condensable (i.e., the liquid mole fraction of nitrogen is zero). Consider the mixture to be ideal, and determine the vapor mole fractions of the three components. (Document any data that you use that is not given in the problem statement.)

Copper was determined in a river sample using spectrometry and the method of standard additions. For the addition, 100.0 μL of a 1000.0 ppm Cu standard was added to 100.0 mL of river water.

Absorbance of river water: 0.572

Absorbance of river water with standard: 1.122

Calculate the concentration of copper in the river water.

Please make sure to display your thought process? It is imperative to be able to follow how the answer was deduced. Please be as thorough as possible. Please address all parts of this question as they are all part and critical to answering this question correctly. Please show good integrity when answering the question:

1. Name 3 indirect methods to measure the miscibility of a polymer/polymer blend

2. Name 3 stress-strain responses to time-dependent deformation

3. Name 3 mechanical models used to calculate the viscoelasticity if polymer/polymer blends

4. Name 2 characteristics of interphases

5. Name 3 factors that affects the interphase concentration profile

6. Name 4 compatibilization methods for polymer blends g) What is dynamic vulcanization?

A membrane consists of a rigid disk of ? = 10 µm thick polycarbonate with 108 identical cylindrical pores, each with ? = 30 nm diameter. The pores pass through the entire membrane thickness normal to the membrane surface. Water (? = 1000 kg/m3 , ? = 10−3 Pa∙s) is forced through the membrane by applying a pressure of 10 atm (absolute) upstream, with 1 atm (absolute) pressure downstream. The pores are sufficiently spaced that flow through each pore is independent of that through all other pores. Furthermore, the pores are sufficiently large that continuum fluid mechanics remains valid. (a) Neglecting minor losses, what is the volume flow rate of water through the membrane? (b) Assuming the flow remains incompressible, what is the maximum pressure difference across the membrane at which the flow would be laminar?