The solar system contains no extrasolar planets
a. True
b. False
Indicate whether the statement is true or false
True
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Steam having a quality of 98% at a pressure of 1.37 × 105 N/m2 is flowing at a velocity of 1 m/s through a steel pipe of 2.7 cm OD and 2.1 cm ID. The heat transfer coefficient at the inner surface, where condensation occurs, is 567 W/(m2 K). A dirt film at the inner surface adds a unit thermal resistance of 0.18 (m2 K)/W. Estimate the rate of heat loss per meter length of pipe if; (a) the pipe is bare, (b) the pipe is covered with a 5 cm layer of 85% magnesia insulation. For both cases assume that the convective heat transfer coefficient at the outer surface is 11 W/(m2 K) and that the environmental temperature is 21°C. Also estimate the quality of the steam after a 3-m length of pipe in both cases
GIVEN
A steel pipe with steam condensing on the inside Diameters
? Outside (Do) = 2.7 cm = 0.027 m
? Inside (Di) = 2.1 cm = 0.021 m Velocity of the steam (V) = 1 m/s Initial steam quality (Xi) = 98% Steam pressure = 1.37 × 105 N/m2 Heat transfer coefficients
? Inside (hci) = 567 W/(m2 K)
? Outside (hco) = 11 W/(m2 K) Thermal resistance of dirt film on inside surface (Rf) = 0.18 (m2 K)/W Ambient temperature (T?) = 21°C
FIND
• The heat loss per meter (q/L) and the change in the quality of the steam per 3 m length for (a) A bare pipe (b) A pipe insulated with 85% Magnesia: thickness (Li) = 0.05 m ASSUMPTIONS
Steady state conditions exist Constant thermal conductivity Steel is 1% carbon steel Radiative heat transfer from the pipe is negligible Neglect the pressure drop of the steam
SKETCH
In which case would the net force due to water pressure on a solid object be greater?
(i) when the object is in water at 100-meter depth (ii) when the object is in water at 200-meter depth
1.(i) 2.(ii) 3.Choices (i) and (ii) would have the same net force due to the water on them. 4.It depends on the orientation of the object.A long hollow cylindrical conductor (inner radius = 2.0 mm, outer radius = 4.0 mm) carries a current of 12 A distributed uniformly across its cross section. A long wire which is coaxial with the cylinder carries an equal current in the same direction. What is the magnitude of the magnetic field 3.0 mm from the axis?
a. 1.1 mT b. 1.4 mT c. 1.7 mT d. 2.0 mT e. 0.2 mT
How does the interstellar medium affect our view of most of the galaxy?
A) It prevents us from seeing most of the galactic disk with visible and ultraviolet light. B) It absorbs all wavelengths of light. C) It produces so much visible light that it blocks our view of anything beyond it. D) It has no effect on visible-light observations, but prevents us from studying the galactic center with radio waves or X-rays.