A spring-powered dart gun is un-stretched and has a spring constant 16.0 N/m. The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun. The velocity of the projectile when it is shot from the gun is
A. 2.04 m/s.
B. 2.75 m/s.
C. 3.50 m/s.
D. 3.75 m/s
E. 4.53 m/s.
E. 4.53 m/s.
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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).
The two main theories of 20th century physics are
A) relativity and quantum theory. B) relativity and Newtonian mechanics. C) quantum theory and electromagnetism. D) relativity and electromagnetism. E) electromagnetism and thermodynamics.
The theory of plate tectonics states that
A) the lithosphere is broken up into several plates that move about as a result of convective motion in the asthenosphere. B) earthquakes and volcanic activity result from convection motion in the lithosphere. C) buoyant lithospheric plates float on top of the rigid asthenosphere. D) the plates move in conveyor-belt fashion as new crust is generated at the continental margins and destroyed at the mid-ocean ridges.
A type of chemical weathering caused by rainwater that has absorbed atmospheric carbon dioxide and formed a weak carbonic acid that slowly dissolves rock is
What will be an ideal response?