Your lungs hold 4.2 L of air at a temperature of 27°C and a pressure of 101.3 kPa. How many moles of air do your lungs hold? (R = 8.31 J/mol ? K)
A) 0.15 moles
B) 0.17 moles
C) 0.19 moles
D) 0.21 moles
E) 0.23 moles
B
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Lunar volcanism is obvious from the huge mare basins, and the more localized ________
Fill in the blank(s) with correct word
Which of the following processes would you expect to produce small-diameter PE fibers that have a very high tensile strength?
(a) Draw fibers from a liquid (b) Draw fibers at a temperature just below the glass transition temperature (c) Draw fibers at a temperature just above the glass transition temperature (d) Draw fibers at room temperature
In a heat exchanger, as shown in accompanying figure, air flows over brass tubes of 1.8- cm-ID and 2.1-cm-OD that contain steam. The convection heat-transfer coefficients on the air and steam sides of the tubes are 70 W/(m2 K) and 210 W/(m2 K), respectively. Calculate the overall heat transfer coefficient for the heat exchanger (a) based on the inner tube area, (b) based on the outer tube area but assume that a fouling factor of 0.00018 (m2 K)/W has developed on the inside of the tube during operation.
GIVEN
• Air flow over brass tube containing steam
• Tube diameters Inside (Di) = 1.8 cm = 0.018 m
Outside (Do) = 2.1 cm = 0.021 m
• Convective heat transfer coefficients Air side h o= 70 W/(m2 K)
Steam side h i= 210 W/(m2 K)
• Fouling factor on the inside of the tube (Rd) = 0.0018 (m2 K)/W
FIND
• The overall heat transfer coefficient for the heat exchanger based on
(a) the inner tube area (Ui) and (b) the outer tube area (Uo)
ASSUMPTIONS
• The heat transfer coefficients are uniform over the transfer surfaces
SKETCH
If the Moon's orbital plane was aligned with the celestial equator we could
a. have eclipses every month. b. never have eclipses. c. have eclipses only at solstice. d. have eclipses only at the equinoxes.