Which of the following is ranked 7 on the Mohs scale?
a. Talc
b. Gypsum
c. Diamond
d. Quartz
d
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An attractive method of energy conservation in industrial settings is to utilize waste heat from largescale power generating equipment. In one such scheme, the exhaust gases from the diesel engine of an industrial power generator are channeled through a cross- flow, compact, waste-heat recovery boiler to produce process steam. In one such heat exchanger, a finned tube bundle is configured with tubes of 2.5 cm outer diameter that are arranged in a staggered equilateral- triangular array with tube center-to-center pitch of 7.5 cm. Engine exhaust gas (thermal properties of which are taken to be the same as those for air) at 400°C is in cross-flow over the tube bank with a free stream velocity of 2.0 m/s. In order to enhance the gas-side convective heat transfer, the tubes have thin circular
fins on their outer surface and the finned surface extension ratio ?=1.15. Due to the steam generation process inside the tubes, their outer surface temperature is 175°C. If there are 10 rows of tubes in the flow direction (NL = 10), calculate the average heat transfer coefficient and pressure drop for the gas flow stream.
GIVEN
FIND
The average heat transfer coefficient (c h) and pressure drop in gas flow stream.
ASSUMPTIONS
Steady state
Tube wall temperature is uniform and constant
SKETCH
PROPERTIES AND CONSTANTS
If extra dimensions do exist, why wouldn't we see obvious evidence for them in everyday life?
a) because they affect only the strength of the strong force andnot of any other forces b) They are the same as the dimensions that we do perceive. c) They will only be present in the distant future. d) They were only present at the time of inflation and before. e) They would be quite small and hard to detect.
The electric field just outside the surface of a hollow conducting sphere of radius 20 cm has a magnitude of 500 N/C and is directed outward. An unknown charge Q is introduced into the center of the sphere and it is noted that the electric field is still directed outward but has decreased to 100 N/C. What is the magnitude of the charge Q?
A. 1.5 nC B. 1.8 nC C. 1.3 nC D. 1.1 nC E. 2.7 nC
If you stand closer to a concave mirror than a distance of one focal length, the image you see is
a. real and inverted. b. real and upright. c. virtual and inverted. d. virtual and upright. e. none of the above because you do not get an image.