A satellite is placed in a geosynchronous orbit. In this equatorial orbit with a period of 24 hours, the satellite hovers over one point on the equator. Which statement is true for a satellite in such an orbit?
A. There is no gravitational force on the satellite.
B. There is no acceleration toward the center of the Earth.
C. The satellite is in a state of free fall toward the Earth.
D. There is a tangential force that helps the satellite keep up with the rotation of the Earth.
E. The force toward the center of the Earth is balanced by a force away from the center of the Earth.
Answer: C
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Water flowing at a rate of 12.6 kg/s is to be cooled from 90 to 65°C by means of an equal flow rate of cold water entering at 40°C. The water velocity with the such that the overall coefficient of heat transfer U is 2300 W/(m2 K). Calculate the heat-exchanger surface area (in square meters) needed for each of the following arrangements: (a) parallel flow, (b) counterflow, (c) a multi-pass heat exchanger with the hot water making one pass through a well-baffled shell and the cold water making two passes through the tubes, and (d) a crossflow heat exchanger with both sides unmixed.
GIVEN
• Warm water cooled by cold water in a heat exchanger
• Both flow rates ( m c) = 12.6 kg/s
• Water temperatures
? Th,in = 90°C
? Th,out = 65°C
? Tc,in = 40°C
• Overall heat transfer coefficient (U) = 2300 W/(m2 K)
FIND
The transfer area (A) for (a) Parallel flow (c) Tube-and-shell; 1 hot shell pass, 2 cold tube passes (b) Counterflow (d) Crossflow–both unmixed
ASSUMPTIONS
• The specific heat is constant
SKETCH
PROPERTIES AND CONSTANTS
the specific heat of water in the temperature range of interest (cp) = 4187 J/(kg K)
The power expended doing 100 J of work in 50 s is
A) 1/2 W. B) 2 W. C) 4 W. D) 50 W. E) 5,000 W.
The Paleozoic era began about how many million years ago?
a. 65 b. 545 c. 245 d. 3
The most widely accepted system of measurement is the metric system
a. True b. False Indicate whether the statement is true or false