課程名稱︰質能平衡甲
課程性質︰系定必修
課程教師︰蔡偉博
開課系所︰化學工程學系
考試時間︰2006/5/23 晚上
是否需發放獎勵金：是的 謝謝^^
（如未明確表示，則不予發放）
試題 :
Note: If you use the attached charts, please indicate the points which you use
for your answers, and turn in the figures.
1.(25 points) Air at 50% relative humidity is cooled isobarically at 1 atm
absolute from 90°C to 25°C.
(a) Estimate the dew point and degrees of superheat of the air at 90°C.
(b) How much water condenses (mol) per cubic meter of feed gas?
(c) Suppose a sample of the 90°C air is put in a closed variable-volume
chamber containing a mirror and the pressure is raised at constant temperature
until a mist forms on the mirror. At what pressure (atm) would the mist form?
(Assume ideal gas behavior.)
2.(15 points) Steam at 260°C and 7.00 bar absolute is expended through a
nozzle to 200°C and 4.00 bar. Negligible heat is transferred from the nozzle
to its surroundings. Calculate the exit steam velocity.
3.(15 points) Methanol is contained in a large tank under a pressure of 3.1 bar
absolute. When a valve on the bottom of the tank is opened, the methanol drains
freely though a 1-cm ID tube whose outlet is 7.00 m below the surface of the
methanol. The pressure at the outlet of the discharge pipe is 1 atm.
(a) Use the Bernoulli equation to estimate the methanol discharge velocity and
flow rate in L/min when the discharge valve is fully opened. Neglect the rate
of fall of the methanol level in the tank.
(b) When the discharge valve is partially closed, the flow rate decreases,which
means that Δu^2/2 changes. However, the other two terms in the Bernoulli
equation (ΔP/ρ and gΔz) remain the same. How do you account for this
apparently contradictory result?
4.(25 points) A system has been devised to store acetonitrile safely at high
pressures and temperatures. The acetonitrile is contained in a 0.2 ft^3 tank
maintained at 4500 psia and 550°F. This tank is placed inside a second tank
whose volume, excluding the volume of the first tank, is 2 ft^3. Nitrogen at
10.0 atm and 550°F is contained in the second tank. Use the compressibility
chart to estimate the final system pressure (atm) if the first tank ruptures
and the final system temperature is 550°F. The critical temperature and
pressure of acetonitrile are 548 K and 47.7 atm, respectively.
5.(15 points)
(a) Using the Txy diagram, estimate the bubble-point temperature and the
equilibrium vapor composition associated with a 40 mole% benzene-60 mole%
toluene liquid mixture at 1 atm. If the mixture is steadily vaporized until the
remaining liquid contains 25% benzene, what is the final temperature?
(b) Using the Txy diagram, estimate the dew-point temperature and the
equilibrium liquid composition associated with a vapor mixture of benzene and
toluene containing 40 mole% benzene at 1 atm. If condensation proceeds until
the remaining vapor contains 60% benzene, what is the final temperature?
6.(15 points) Five kilograms of a 30 wt% acetone-70 wt% water mixture is added
to 3.5 Kg of a 20 wt% acetone-80 wt% MIBK mixture at 25°C . Use Figure 6.6-1
to estimate the mass and composition of each phase of resulting mixture.
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 140.112.240.230