Chemical Engineering Answers

8. Use the steam tables to calculate the enthalpy change (in kJ) of 2 kg-mol of water/steam when heated from:

a) 293 K & 100 kPa to 303 K & 100 kPa.

b) 400 K & 100 kPa to 900 K & 100 kPa..

When the slope of operating line of the rectifying section of distillate column equal to unity?

Two streams of water are mixed to form the feed to a boiler. Process data are as follows:

Feed streams 1: 100 kg/min@30C

Feed streams 2: 195 kg/min@65C

Boiler pressure : 17 bar absolute

Calculate the required heat input to the boiler in kJ/min if the emerging steam is saturated at the boiler pressure. Neglect the kinetic energy, potential energy and work.

Your final answer must be in 1 decimal place with unit kJ/min.

A vapor-compression refrigeration machine uses refrigerant-134a as much as 2 kg/min with operating conditions leaving the evaporator at a temperature of -14°C and a condenser pressure of 0.8 Mpa. Determine the COP value and cooling load of the machine.

Pure water was used to remove 90% ammonia from the gas mixture in packed bed tower. The gas

mixture which contain 5 mol% NH 3 enters from the bottom of the column at flow rate of 100 kmol/h.

Pure water enters from the top of the column at a flow rate 1.5 times minimum pure water flow rate

(1.5 L’ min ). The column cross sectional area is 0.20 m 2 . The equilibrium relationship for NH 3 and water

is given by y = 0.8915x. The film mass transfer coefficients are given as k’ y a = 0.0739 kmol/s.m 3 and

k’ x a = 0.169 kmol/s.m 3 . Determine the height of the packed tower using liquid film mass transfer

coefficient, k’ x a.

The speed of the butadiene dimerization reaction was investigated by measuring the total pressure in a batch reactor operating isothermally at a temperature of 326 degrees Celsius. The measurement results are as follows:

t (minutes) 0 5 10 15 20 25 30 35 40 45 50 55 60 70

Pt (mmHg) 632 611 552 573.5 558.5 545 533.5 523 514 505 497 490 484 473

Calculate the order reaction and the rate constant for the reaction. Then the equation for the rate of reaction

Two streams of water are mixed to form the feed to a boiler. Process data are as follows:

Feed streams 1: 100 kg/min@30C

Feed streams 2: 195 kg/min@65C

Boiler pressure : 17 bar absolute

Calculate the required heat input to the boiler in kJ/min if the emerging steam is saturated at the boiler pressure. Neglect the kinetic energy, potential energy and work.

Your final answer must be in 1 decimal place with unit kJ/min.

A superheated steam at 10 bar absolute with 150 °C is fed to a boiler at rate of 200

kg/min. It is desired to produce new superheated steam at 250°C and 10 bar with rate of

407.42 kg/min that emerge at position of 50 m higher than the inlet stream by mixing the

inlet superheated steam at 10 bar absolute with a second stream of saturated steam at

10 bar and 207.42 kg/min. Determine the heat input to the boiler (kJ/s)

Calculate the work done for the adiabatic compression of ethane from 150 kPa to 600 kPa

at 20°C. Assume ethane to be an ideal gas. The heat capacity of ethane is given by

𝐶𝑝

0= 1.48 + 4.124 X 10-2 T + 1.23 X 10-5 T

2

- 1.74 X 10-9 T

3

( T in K, Cp = Cal/mol-K)

The reservoir problem containing 45 kg of liquid with an initial temperature of 45 ° C has one inlet and one outlet equal to the mass flow rates. Liquid water enters at 45 ° C and a mass flow rate of 270 kg / h. A water-cooled cooling coil dissipates energy at a speed of 7.6 kW. The water is mixed well with the help of a vane wheel so that the water temperature is uniform everywhere. The input power from the impeller to the water is 0.6 kW. Inlet and outlet pressures are equal and all kinetic energy and potential effects can be ignored. Determine changes in water temperature over time.