Which of the following atoms normally has one covalent bond to it?
a. Br
b. O
c. C
d. P
e. Ne
a
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An electronic device is cooled by passing air at 27°C through six small tubular passages in parallel drilled through the bottom of the device in parallel as shown. The mass flow rate per tube is 7 × 10–5 kg/s. Heat is generated in the device resulting in approximately uniform heat flux to the air in the cooling passage. To determine the heat flux, the air outlet temperature is measured and found to be 77°C. Calculate the rate of heat generation, the average heat transfer coefficient, and the surface temperature of the cooling channel at the center and at the outlet.
GIVEN
• Air flow through small tubular passages as shown above
• Air temperature
? Entrance (Tb,in) = 27°C
? Exit (Tb,out) = 77°C
• Mass flow rate per passage (m )= 7 × 10–5 kg/s
• Number of passages (N) = 6
FIND
(a) The rate of heat generation ( Q
G) (b) The average heat transfer coefficient ( h c) (c) Cooling channel surface temperature at the center (Ts,c) (d) Cooling channel surface temperature at the outlet (Ts,out)
ASSUMPTIONS
• Steady state
• Uniform heat generation
• Uniform heat flux to the air
• Viscosity variation is negligible
• Heat transfer coefficient is approximately constant axially
PROPERTIES AND CONSTANTS
for dry air at the average bulk temperature of 52°C
Specific heat (c) = 1016 J/(kg K) ]
Thermal conductivity (k) = 0.0273 W/(m K)
Absolute viscosity (?) = 19.593 × 10–6 (Ns)/m2
Prandtl number (Pr) = 0.71
The sketch shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents the entire main sequence, while (c) and (d) represent only small parts of the main sequence. Which group represents stars that are extremely luminous and emit most of their radiation as ultraviolet light?
A) a B) b C) c D) d E) e
A star's motion across the sky is its ________ motion
Fill in the blank(s) with correct word