Midterm Exam

Q1     (25 points)

Saturated steam at 200 °C exchanges heat with a cold gas stream in a heat exchanger.  The gas stream is an equimolar mixture of methane and ethane.  The gas mixture enters the tube side of the heat exchanger at 25 °C and 1.1 bar and leaves at 100 °C and 1.0 bar.  The steam condenses and leaves the shell side of the heat exchanger as a liquid at 40 °C.  The volumetric flow rate of the inlet gas mixture is 500 m3/min.  Calculate

a)      The mass flow rate of the gas mixture.

b)      The rate of heat transferred to the gas stream.

c)      The volumetric flow rate of the inlet steam.

State all assumptions.

Q2     (25 points)

9.0 kg of saturated steam is in equilibrium with 1.0 kg of saturated water in a 1-m3 rigid vessel at 1 bar.  Calculate

a)      the heat required to completely evaporate the liquid and the final pressure and temperature in the vessel.

b)      the heat required to completely evaporate the liquid and the final volume and temperature of the vessel if the process is performed at constant pressure (ie. the water is contained in a cylinder with a movable piston that maintains the pressure at 1 bar).

State all assumptions.

Q3     (25 points)

A stream consisting of 40 mol % acetone and 60 mol % water at 20 °C and 1 bar with a flow rate of 100 mol/s is to be heated at constant pressure to 500 °C.  Calculate the heating duty of the process (kW).  State all assumptions.

Q4     (25 points)

An air conditioner cools a stream of humid air at 45 ºC and 50 % relative humidity to a temperature ten-degree below the dew point temperature.  The process is performed at constant pressure of 1 atm.  If the cooling duty of the air conditioner is 4 tons calculate the volumetric flow rate of the inlet humid air and the rate of condensation of water.

State all assumptions.