The central engine for active galaxies is believed to be a(n) ________
Fill in the blank(s) with correct word
supermassive black hole
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Water at 80°C is flowing through a thin copper tube (15.2-cm-ID) at a velocity of 7.6 m/s. The duct is located in a room at 15°C and the heat transfer coefficient at the outer surface of the duct is 14.1 W/(m2 K). (a) Determine the heat transfer coefficient at the inner surface. (b) Estimate the length of duct in which the water temperature drops 1°C.
GIVEN
• Water flowing through a thin copper tube in a room
• Water temperature (Tb) = 80°C
• Inside diameter of tube (D) = 15.2 cm = 0.152 cm
• Water velocity (V) = 7.6 m/s
• Room air temperature (T?) = 15°C
• Outer surface heat transfer coefficient ( h co ) = 14.1 W/(m2 K)
FIND
(a) The heat transfer coefficient at the inner surface ( h ci )
(b) Length of duct (L) for temperature drop of 1°C
ASSUMPTIONS
• Steady state
• Thermal resistance of the copper tube is negligible
• Fully developed flow
SKETCH
PROPERTIES AND CONSTANTS
for water at 80°C
Density (?) 971.6 kg/m3
Thermal conductivity (k) = 0.673 W/(m K)
Absolute viscosity (?) = 356.7 × 10–6 (Ns)/m2
Prandtl number (Pr) = 2.13
Specific heat (c) = 4194 J/(kg K)
Which is a possible value for the principal quantum number n?
a. 3.14 b. 7 c. 2.5 d. None of these
A person has a thermal conductivity of 0.18 W/m·K between his inner core and his skin with an effective shell thickness of 1.30 cm between his core and skin. If his inner core is at the normal 98.6°F, and his skin has a surface area of 1.62 m2, what will be his rate of loss of thermal energy due to conduction through his skin if his skin temperature is 28.3°C?
a. 150 W b. 158 W c. 316 W d. 195 W e. 254 W
If the temperature changes by 36
then what is the change in temperature in Celsius?
A. 40
B. 32
C. 26
D. 20
E. 15