On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, how long has human civilization (i.e., since ancient Egypt) existed?
A) a few seconds
B) about a month
C) less than a millionth of a second
D) a few hours
E) about half the year
A
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The test data tabulated on the next page were reduced from measurements made to determine the heat-transfer coefficient inside tubes at Reynolds numbers only slightly above transition and at relatively high Prandtl numbers (as associated with oils). Tests were made in a double-tube exchanger with a counterflow of water to provide the cooling. The pipe used to carry the oils was 1.5 cm-OD, 18 BWG, 3 m-long. Correlate the data in terms of appropriate dimensionless parameters.
Hint: Start by correlating Nu and ReD irrespective of the Prandtl numbers, since the influence of
the Prandtl number on the Nusselt number is expected to be relatively small. By plotting Nu vs.
Re on log-log paper, one can guess the nature of the correlation equation, Nu = f1 (Re). A plot of
Nu/f1 (Re) vs. Pr then reveals the dependence upon Pr. For the final equation, the influence of
the viscosity variation also is considered.
GIVEN
Oil in a counterflow heat exchanger
Pipe specifications: 1.5 cm-OD, 18 BWG
Pipe length (L) = 3 m
The experimental data above
FIND
Correlate the data in terms of appropriate dimensionless parameters
ASSUMPTIONS
The data represents the steady state for each case
PROPERTIES AND CONSTANTS
From Appendix 2, Table 42: for 1.5 cm OD, 18 BWG tubing, the inside diameter D = 1.338 cm
What are the formula masses of water, H20; propene, C3H6; and 2-propanol, C3H8O?
A) water: 18 amu; propene: 40 amu; 2-propanol: 58 amu B) water: 18 amu; propene: 42 amu; 2-propanol: 62 amu C) water: 18 amu; propene: 42 amu; 2-propanol: 60 amu D) water: 18 amu; propene: 44 amu; 2-propanol: 64 amu
An observer in the Northern Hemisphere takes a time exposure photograph of the night sky. If the illustration below depicts the photograph taken by the observer, which direction was the camera pointing?
a.
straight north
b.
straight east
c.
straight south
d.
straight west
e.
straight up, directly overhead
The graph shows how a star's orbital speed varies with time because of the gravitational tug of an orbiting planet. Based on these data, the planet's orbital period is about
A) 2 days. B) 4 days. C) 6 days. D) 50 days.