Give the Kelvin-Planck statement of the Second Law of Thermodynamics
What will be an ideal response?
No device is possible whose sole effect is to transform a given amount of heat completely into work.
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Compare the rate of heat transfer and the pressure drop for an in-line and a staggered arrangement of a tube bank consisting of 300 tubes, 1.8 m long and 2.5 cm OD. The tubes are to be arranged in 15 rows with longitudinal and transverse spacing of 5 cm. The tube surface temperature is 95°C and water at 35°C is flowing at a mass rate of 5400 kg/s over the tubes.
GIVEN
Water flowing over an in-line and a staggered tube bank
Number of tubes (Nt) = 300
Length of tubes (L) = 1.8 m
Tube outside diameter (D) = 2.5 cm= 0.025 m
Number of rows (N) = 15
Normal and parallel spacing = 5 cm=0.05 m
Tube surface temperature (Tt) = 95°C
Water inlet temperature (Tw,in) = 35°C
Mass flow rate of water (m) = 5400 kg/s
FIND
(a) Compare the rate of heat transfer (q) and
(b) The pressure drop ( ?p) for the two configurations
ASSUMPTIONS
Steady state
Tube temperature is uniform
SKETCH
PROPERTIES AND CONSTANTS
for water at the inlet temperature of 35°C
Density (?) = 994.1 kg/m3
Thermal conductivity (k) = 0.624 W/(m K)
Prandtl number (Pr) = 4.8
Specific heat (c) = 4175 J/(kg K)
At the tube temperature of 95°C
Prs = 1.88
Which of the following methods allows us to determine the size of an extrasolar planet around another star?
A) detection of brightness changes in a star as a planet passes in front of it B) detection of reflected starlight C) regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky D) detection of Doppler shifts in the spectra of the parent stars
Suppose you wish to lower the pitch of a violin string by 2 octaves. This could be done by
A) reducing the string tension by a factor of four. B) shortening the string length to a quarter as much. C) replacing the string with one of the same material only half as massive. D) replacing the string with one of the same material but with quadruple the diameter. E) increasing the string tension a factor of four.
Describe two ways light can be separated out into its component colors in detail for spectroscopic analysis
What will be an ideal response?