What is the most geologically active object we know of in the solar system?
a. Earth
b. Mercury
c. Mars
d. Jupiter
e. Io
Answer: e. Io
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Our best close-up views of the jovian moons came from the many passes by:
A) Voyager 2. B) Galileo. C) Cassini. D) New Horizons. E) Global Surveyor.
Exhaust gases from a power plant are used to preheat air in a cross-flow heat exchanger. The exhaust gases enter the heat exchanger at 450°C and leave at 200°C. The air enters the heat exchanger at 70°C, leaves at 250°C, and has a mass flow rate of 10 kg/s. Assume the properties of the exhaust gases can be approximated by those of air. The overall heat transfer coefficient of the heat exchanger is 154 W/(m2 K). Calculate the heat exchanger surface area required if (a) the air is unmixed and the exhaust gases are mixed and (b) both fluids are unmixed.
GIVEN
• Cross-flow heat exchanger – exhaust gas to air
• Exhaust temperatures
? Te,in = 450°C
? Te,out = 200°C
• Air temperatures
? Ta,in = 70°C
? Ta,out = 250°C
• Air flow rate m a= 10 kg/s
• Overall heat transfer coefficient (U) = 154 W/(m2 K)
FIND
The heat exchanger surface area (A) if
(a) Air is unmixed, exhaust is mixed
(b) Both are unmixed
ASSUMPTIONS
• The properties of the exhaust gases can be approximated by those of air
• The air is in the tube
SKETCH
PROPERTIES AND CONSTANTS
the specific heat of air at the mean temperature of 160°C (cpa)
What is the escape speed from a planet of mass m and radius r if m = 3.2 × 1023 kg and r = 2.4 × 106 m?
A. 5.5 km/s B. 4.2 km/s C. 5.2 km/s D. 4.8 km/s E. 3.7 km/s
Explain coronae
What will be an ideal response?