Radiation Activity: The half-life of radioactive iodine-137 is 8.0 days. How many iodine nuclei are necessary to produce an activity of 1.0 ?Ci? (1 Ci = 3.70 × 1010 Bq)
A. 2.9 × 109
B. 4.6 × 109
C. 3.7 × 1010
D. 7.6 × 1012
Answer: C
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PVC with a(n) _____________arrangement of Cl atoms substituting for hydrogen on the LCM is difficult to crystallize.
Fill in the blank(s) with the appropriate word(s).
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
The central star of the Crab Nebula has now collapsed into a ________, whose energy keeps this famous nebula visible even in binoculars
Fill in the blank(s) with correct word
The water level in a reservoir is maintained at a constant level. What is the exit velocity in an outlet pipe 3.0 m below the water surface?
a. 2.4 m/s b. 3.0 m/s c. 5.4 m/s d. 7.7 m/s e. 49 m/s