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Mass flow through a sonic nozzle is a function of gas pressure and
temperature. For a given pressure *p* and temperature *T*,
mass flow rate through the nozzle is given by the equation:

where *m* is in lb_{m}/min, *p* is in atm, and *T* is in °R.

(a) Identify the unit for the constant ‘0.0853’.

(2 marks)

(b) Determine the new expression of the equation, if *m*, *p*
and *T* are expressed in g/hr, mmHg and K, respectively.

(8 marks)

Formic acid, CH_{2}O_{2} (MW=46.025) is a colorless, clear,
corrosive liquid with a pungent odor. It is widely used in used textiles
and leather processing industries. For a given 75 wt % formic acid solution
of specific gravity 1.86:

(a) Identify the mole fraction composition of this solution with a basis of 385 g solution.

(4 marks) (b) Estimate the volume (in gallons) of 3 mol CH_{2}O _{2 }solution.

(6 marks)

The heat capacity of liquid pentane is represented by the following correlation:

Express the correlation for C_{p} with the unit Btu/(lb-mol.°R) in
terms of T in °R. [Hint: 1 lb-mole = 454 gmol]

(9 marks)

A differential manometer filled with manometer fluid X is used to measure
the pressure drop between two points in a process line containing liquid
glycerol, C_{3}H_{8}O_{3} (SG=1.260). The pressure
drop is found to be 13.5 mm Hg with the reading of the differential
manometer is shown in Figure 4(a). In another occasion, a sealed end
manometer (Figure 4(b)) containing manometer fluid X is used to measure the
atmospheric pressure. Estimate *h* in cm, if the atmospheric
pressure is 745 mm Hg.

(6 marks)

Evaporation and recycling systems are adopted in the calcium chloride (CaCl _{2}) crystallization process. The simplified process flow diagram
is depicted in Figure Q1.

The recycled stream (R) is maintained at the composition of 0.7 kg CaCl _{2}/kg H_{2}O.

Figure Q1

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(a) Sketch a completely labelled process flow diagram (with compositions) for the process.

(8 marks) (b) Compute the mass flow rate (kg/hr) of stream W, R and D, respectively.

(8 marks) (c) In the case of evaporator failure, it is found that the
evaporator can only cope with the water evaporation rate (W) of 1.5 lb_{m}/s. Estimate the new feed flow rate (F) required (lb _{m}/s) and the formation rate (lb_{m}/s) of crystal
product (P), if the composition of all streams is to be remained unchanged.

(4 marks)

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A proposed process to remove H_{2}S is by the reaction with SO _{2} through the following equation:

2𝐻_{2}𝑆(𝑔)+𝑆𝑂_{2}(𝑔)→3𝑆(𝑠)+2𝐻_{2}𝑂(𝑔)

In a test of the process, a gas stream containing 20 mole % H_{2}S
and 80 mole % CH_{4} is combined with a stream of pure SO _{2}. The process produces 3500 g of S (s) in an hour. In the
product gas, the ratio of SO_{2} to H_{2}S equals to 2 and
the ratio of H_{2}O to H_{2}S is 5.

(a) Calculate the extent of reaction (mol/hr) of the process.

(3 marks)

(b) Determine the molar flow rates (mol/hr) for both feed gas streams and all components in the product gas stream by using extent of reaction method.

(12 marks) (c) Identify the limiting reactant.

(3 marks)

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A stream of 100 kg/min superheated steam enters a turbine at 20 bar and
450°C at a linear velocity of 80 m/s and leaves at a point 2 m below the
turbine inlet at 5 bar and a velocity of 350 m/s. The heat loss from the
turbine is estimated to be negligible, while the turbine develops 1800 kW
of work. Determine the specific enthalpy, 𝐻̂ (kJ/kg) of the turbine outlet
stream, if the 𝐻̂_{in} of the inlet stream is 3358 kJ/kg.

(12 marks)

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**END OF QUESTION PAPER **

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