Two fireworks explode at the same position on the 4th of July. A stationary observer notices that the time interval between the two events was 5.00 seconds. A second observer flies past the fireworks at a speed of 0.600c. What value does she obtain when she measures the time interval between the two explosions?
a. 8.33 s
b. 6.25 s
c. 4.00 s
d. 3.00 s
e. 5.00 s
b
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Hot water is to be heated from 10 to 30°C, at the rate of 300 kg/s by atmospheric pressure steam in a single-pass shell-and-tube heat exchanger consisting of 1-in. schedule 40 steel pipe. The surface coefficient on the steam side is estimated to be 11,350 W/(m2 K). An available pump can deliver the desired quantity of water provided the pressure drop through the pipes does not exceed 15 psi. Calculate the number of tubes in parallel and the length of each tube necessary to operate the heat exchanger with the available pump.
GIVEN
Single-pass shell-and-tube heat exchanger Water is heated by atmosphere steam Water temperatures
? Tw,in = 10°C
? Tw,out = 30°C Water flow rate ( m w)= 300 kg/s Inner tube: 1 in. schedule 40 steel pipe Maximum water pressure drop (?p) = 15 psi = 103,422 N/m2 Steam side heat transfer coefficient ( oh ) = 11,350 W/(m2 K)
FIND
(a) The number of tubes in parallel (N)
(b) The length of each tube (L)
ASSUMPTIONS The tube is smooth The tube is 1% carbon steel Uniform pipe surface temperature Fully developed flow in pipe Water flow is turbulent to insure good heat transfer
SKETCH
PROPERTIES AND CONSTANTS
for 1 in. schedule 40 pipe
Inside diameter (Di) = 1.049 in. = 0.0266 m
Outside diameter (Do) = 1.315 in. = 0.0334 m
the saturation temperature of steam at 1 atm = 100°C
for water at the average temperature of 20°C
Absolute viscosity (?) = 993 × 10–6 Ns/m2
Density (?) = 998.2 kg/m3 Specific heat (cpw) = 4182 J/(kg K)
Thermal conductivity (kw) = 0.597 W/(m K)
Prandtl number (Pr) = 7.0,
the thermal conductivity of 1% carbon steel (ks) = 43 W/(m K).
Based on our current understanding of physics, we can understand the conditions that prevailed in the early universe as far back in time as about
A) 380,000 years after the Big Bang. B) one ten-billionth of a second after the Big Bang. C) 10-45 seconds after the Big Bang. D) 10 billion years ago.
Velocity: If you run a complete loop around an outdoor track of length 400 m in 100 s, find your(a) average velocity and (b) average speed.
Fill in the blank(s) with the appropriate word(s).
A huge bull's-eye formation is a distinctive feature of Jupiter's moon ______________
Fill in the blank(s) with correct word