Two ways that the internal energy of a substance can be increased are __________ and __________
Fill in the blank(s) with correct word
doing work on it, adding heat to it
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The _______________ formula expresses the relationship of the linear (true) diameter, the angular (apparent) diameter, and the distance, of any object
Fill in the blank(s) with correct word
One common technique used to discover the presence of an extrasolar planet around a star is to detect how they tug their stars about, creating small Doppler shifts in the stars' spectra
a. True b. False Indicate whether the statement is true or false
Suppose that the speed of an electron traveling 1.0 km/s is known to an accuracy of 1 part in 105 (i.e., within 0.01%). What is the greatest possible accuracy within which we can determine the position of this electron?
What will be an ideal response?
An engineer is designing a heating system that consists of multiple tubes placed in a duct carrying the air supply for a building. She decides to perform preliminary tests with a single copper tube, 2-cm-O.D., carrying condensing steam at 100°C. The air velocity in the duct is 5 m/s and its temperature is 20°C. The tube is placed normal to the flow, but it may be advantageous to place the tube at an angle to the air flow and thus increase the heat transfer surface area. It the duct width is 1 m, predict the outcome of the planned tests and estimate how the angle ? will affect the rate of heat transfer. Are there limits?
GIVEN
• A copper tube carrying condensed steam in an air duct
• Tube outside diameter (D) = 2 cm = 0.02 m
• Steam temperature (Ts) = 100°C
• Air velocity (U?) = 5 m/s
• Air temperature (T?) = 20°C
• Duct width (w) = 1 m
FIND
• Is it more advantageous to have the tubes normal to the air flow or at some angle to the air flow?
ASSUMPTIONS
• Steady state
• Air velocity in the duct is uniform
• Thermal resistance due to steam condensing is negligible
• Thermal resistance of the tube wall is negligible
SKETCH
PROPERTIES AND CONSTANTS
Thermal conductivity (k) = 0.0251 W/(m K) Kinematic viscosity
(?) = 15.7 × 10–6 m2/s Prandtl number (Pr) = 0.71