The main source of Earth's natural heat is
A) molten-hot lava.
B) pressure on Earth's interior.
C) radioactivity in Earth's interior.
D) solar energy in the form of fossil fuels.
Answer: C
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What is the fluid transport factor?
What will be an ideal response?
Estimate the heat transfer coefficient for liquid sodium at 540°C flowing over a 10-row staggered-tube bank of 2.5 cm-diameter tubes arranged in an equilateral- triangular array with a 1.5 pitch-to-diameter ratio. The entering velocity is 0.6 m/s, based on the area of the shell, and the tube surface temperature is 200°C. The outlet sodium temperature is 310°C.
GIVEN
FIND
Estimate the heat transfer coefficient (c h)
ASSUMPTIONS
Steady state
The correlation can be applied to a pitch-to-diameter ratio of 1.5
Tube wall temperature is uniform and constant
SKETCH
PROPERTIES AND CONSTANTS
Density (?) = 847 kg/m3
Specific heat (c)=1285 W/(kg K)
Thermal conductivity (k) = 70.1W/(m K)
Kinematic viscosity (?)= 2.92*10-7 m2/s
Prandtl number (Pr) = 0.0047
What is gravitational lensing?
A. the temporary disappearance of a star as an object passes in front of it B. the use of Earth's gravity to shape lenses during grinding C. the focusing and brightening of starlight by the gravitational field of a foreground object D. the use of small telescopes to enhance the brightness of stars
A 2.0 ?F capacitor is charged to 12. V and then discharged through 4 × 106 ?. How long will it take for the voltage across the capacitor to drop to 3.0 V?
What will be an ideal response?