A debris disk is a disk of dust found by infrared observations around some stars
Indicate whether the statement is true or false
True
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A compound microscope has an eyepiece that
a. uses a real image from the objective as the object and forms its own real image. b. uses a real image from the objective as the object and forms a virtual image. c. uses a virtual image from the objective as the object and forms its own real image. d. uses a virtual image from the objective as the object and forms its own virtual image.
Evidence that molecules of a gas are in constant motion is:
A. winds exert pressure B. two gases interdiffuse quickly C. warm air rises D. energy as heat is needed to vaporize a liquid E. gases are easily compressed
Hydrogen gas seems to have a diffusivity of about 2.6 x 10^-13 m^2/s when diffusing into iron at 770 K. What would you expect the rate of diffusion or mass flow rate per unit area of hydrogen to be when stored in an iron container at 5 atmospheres pressure, assuming the density of hydrogen at 1 mm in the iron from the containing surface to be 5% of the normal hydrogen density, given by p/RT?
What will be an ideal response?
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