A black hole consists of a large ________ in a small space.
Fill in the blank(s) with the appropriate word(s).
mass
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Which of the following explains why, about 13,000 years from now, Vega will be a better North Star than Polaris?
A) Earth rotates once each day. B) Earth orbits the Sun once each year. C) The direction of Earth's axis in space precesses with a period of about 26,000 years. D) Stars appear to move randomly relative to our Sun in the local solar neighborhood. E) The universe is expanding.
Which list includes only units of the U.S. customary system?
a. kilograms, micrometers, milliseconds b. pounds, kilometers, nanoseconds c. grams, feet, minutes d. pounds, centimeters, seconds e. ounces, inches, seconds
Oil c p2.1 kJ/(kg K) is used to heat water in a shell and tube heat exchanger with a single shell and two tube passes. The overall heat transfer coefficient is 525 W/(m2 K). The mass flow rates are 7 kg/s for the oil and 10 kg/s for the water. The oil and water enter the heat exchanger at 240°C and 20°C, respectively. The heat exchanger is to be designed so that the water leaves the heat exchanger with a minimum temperature of 80°C. Calculate the heat transfer surface area required to achieve this temperature.
GIVEN
• Oil heats water in a heat exchanger with one shell pass and two tube passes
• Oil specific heat (cpo) = 2.1 kJ/(kg K) = 2100 J/(kg K)
• Overall heat transfer coefficient (U) = 525 W/(m2 K)
• Oil mass flow rate m o= 7 kg/s
• Water mass flow rate m w= 10 kg/s
• Inlet temperatures: Oil (To,in) = 240° Water (Tw,in) = 20°C
• Minimum water outlet temperature (Tw,out) = 80°C
FIND
• The heat transfer area (A) required
ASSUMPTIONS
• Oil is in the tubes
SKETCH
PROPERTIES AND CONSTANTS
the specific heat of water at the average temperature of 50°C (cpw)= 4178 J/(kg K)
Jupiter's atmosphere is a single huge storm system
Indicate whether the statement is true or false