Which of the following is an example of a chemical property?
a. Al has a density of 2.70 g/cm3.
b. Diamond is the hardest substance known.
c. Limestone will yield CO2 when heated.
d. CO2 will freeze at –78°C.
c
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Reconsider the heat exchanger and explore the effect of tube center-to- center spacing in the equilateral array of the finned tubes. Consider the tube spacing of 8.75 cm and 10 cm. What is the extent of change in the average heat transfer coefficient and pressure drop? Likewise, what is the extent of change in the thermal and hydrodynamic performance if a square pitch (inline arrangement is considered) with tube center-to-center spacing of 7.5 cm?
GIVEN
Heated air flowing over an equilateral staggered tube bank
Exhaust gas temperature
Tair,in = 400°C
Number of tube rows (NL) = 10
Tube diameter (D) = 2.5 cm= 0.025 m
Center to center pitch(S) = 7.5 cm=0.075 m
Free stream velocity (Ua) = 2 m/s
Tube surface temperature (Tt) = 175°C
Finned surface extension ration (?)= 1.15
FIND
The average heat transfer coefficient (c h) and pressure drop in gas flow stream.
ASSUMPTIONS
Steady state
Tube wall temperature is uniform and constant
SKETCH
An aquarium contains a 5-cm layer of water (n = 1.333) floating on top of carbon tetrachloride (n = 1.461). If the angle of incidence into the water from the carbon tetrachloride is 20°, what is the angle of refraction into the air?
a. 20° b. 30° c. 38° d. 69° e. 26°
A dead-end page is a term for a one-page website.
Answer the following statement true (T) or false (F)
Gwen releases a rock at rest from the top of a 40-m tower. If g = 9.8 m/s2 and air resistance is negligible, what is the speed of the rock as it hits the ground?
a. 28 m/s b. 14 m/s c. 20 m/s d. 40 m/s e. 780 m/s