The pressure relief valve is opened on a thin-walled cylindrical tank, with the radius-to-wall thickness ratio of 128, thereby decreasing the longitudinal strain by 150 3 1026. Assume E 5 73 GPa and ? 5 0.33. The original internal pressure in the tank was approximately:
(A) 370 kPa
(B) 450 kPa
(C) 500 kPa
(D) 590 kPa
(C) 500 kPa
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A circumferential fin of rectangular cross section, 3.7-cm-OD and 0.3-cm-thick surrounds a 2.5- cm-diameter tube as shown below. The fin is constructed of mild steel. Air blowing over the fin produces a heat transfer coefficient of 28.4 W/(m2 K). If the temperatures of the base of the fin and the air are 260°C and 38°C, respectively, calculate the heat transfer rate from the fin.
GIVEN
FIND
ASSUMPTIONS
The system has reached steady state
The mild steel is 1% carbon steel
The thermal conductivity of the steel is uniform
Radial conduction only (temperature is uniform across the cross section of the fin)
The heat transfer from the end of the fin can be accounted for by increasing the length by half the
thickness and assuming the end is insulated
SKETCH
PROPERTIES AND CONSTANTS
Thermal conductivity of 1% carbon steel (k) = 43 W/(m K) at 20°C
The best way to increase the tensile strength of a polycrystalline ceramic is to
(a) Decrease the grain size (b) Add alloy elements (c) Decrease porosity (d) Solution treat, quench, and age
The radioactivity from your body
A. does not cause cancer because it is natural B. is responsible for more than half of the cancer in humans C. does cause cancer, but at a very low rate D. helps reduce natural cancer, just as radiation therapy does
A carbon resistor has a resistance of 18 ? at a temperature of 20°C. What is its resistance at a temperature of 120°C? (The temperature coefficient of resistivity for carbon is -5.0 × 10-4 /C°.)
A) 18 ? B) 17 ? C) 16 ? D) 15 ? E) 14 ?