10-202
Spring, 2013
Special Homework Problems - Page 2
Problems selected from JWW's old quizs and exams.
Problem #5 - Determine the following values from data in the book or handouts:
a) Determine the enthalpy change as ammonia condenses at 240K in terms of kJ/g.
b) Determine the enthalpy change in terms of kJ/g„, as ethylene vapor is heated from 300K
to 450K at 1 atmosphere pressure.
c) Determine the enthalpy change in terms of BTU/pound as oxygen is cooled from 950 °F to
500°F at I atmosphere pressure.
d) Determine the enthalpy change in terms of BTU/pound as liquid water at 80 °F and 1.0
atmosphere is heated to saturated steam at 280 °F, what is the pressure at this point.
e) Using Kopp's Rule determine the enthalpy change as 1 gram mole of oxalic acid (solid) is
heated from 15 °C to 35 °C.
Problem # 6 - Air at a dry bulb temperature of 44 °C and a temperature wet bulb of 28 °C is first to
be heated to 105 ° C and then used to supply heat to a drying oven. In the drying oven the
air picks up moisture and cools in an adiabatic manner until it reaches 40% relative humidity
at which condition it exits. Determine the following:
a) The dew point temperature and humidity of the inlet fresh air.
b) The energy required in kJ/kg dry air to heat the air in the heater
c) The specific volume of air m 3/kg dry air leaving the hearer
d) The amount of water in kg/kg dry air evaporated in the drier
e) The exit temperature of the air leaving the drier in °C
Problem #7 - To recover ethanol and kill any remaining yeast cells, the broth from a fermentation
process at 60° F and 20% by weight ethanol (the remainder being water) is mixed at a rate of
75 pounds per hour with 50 psia saturated steam with a flow rate of 25 pounds per hour. To
ensure that the mixture is hot enough to deactivate the yeast an electrical heater adds 28,000
BTU/hour to the mixture. Using the ethanol-water chart provided in the appendix of the text
and the inverse lever arm rule method of solution, answer the following questions
concerning the phase separation tank:
a) Temperature in the phase separation tank:
b) For the vapor state; flow rate of vapor:
ethanol concentration:
c) For the liquid state; flow rate of liquid:
ethanol concentration:
lbs/hr
lbs/hr