Increasing the diameter of a telescope I. increases its light gathering power. II. increases its resolving power. III. increases it magnifying power. IV. increases its chromatic aberration
a. I, II, III, & IV
b. I, II, & III
c. I, II, & IV
d. III & IV
e. I & II
E
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Water flowing at a rate of 10 kg/s through 50 tubes double-pass shell and tube heat exchanger heats air that flows through the shell side. The length of the brass tubes is 6.7 m and they have an outside diameter of 2.6 cm and an inside diameter of 2.3 cm. The heat transfer coefficient of the water and air are 470 W/(m2 K) and 210 W/(m2 K), respectively. The air enters the shell at a temperature of 15°C and a flow rate of 16 kg/s. The temperature of the water as it enters the tubes is 75°C. Calculate (a) the heat exchanger effectiveness, (b) the heat transfer rate to the air, and (c) the outlet temperature of the air and water.
GIVEN
• Shell-and-tube heat exchanger - one shell, two tube passes
• Water in brass tubes, air in shell
• Water flow rate ( m w)= 10 kg/s
• Number of double passes (N) = 50
• Tube length (L) = 6.7 m
• Tube diameters
? Do = 2.6 cm = 0.026 m
? Di = 2.3 cm = 0.023 m
• Heat transfer coefficient
? Water ( )ih = 470 W/(m2 K)
? Air ( )oh = 210 W/(m2 K)
• Air inlet temperature (Ta,in) = 15°C
• Air flow rate ( m a)= 16 kg/s
• Water inlet temperature (Tw,in) = 75°C
FIND
(a) Effectiveness (e)
(b) The heat transfer rate (q)
(c) Outlet temperatures (Ta,out, Tw,out)
ASSUMPTIONS
• Tube length includes both passes
SKETCH
OPERTIES AND CONSTANTS
the specific heat of water at 75°C (cpw) = 4190 J/(kg K)
the specific heat of air at 15°C (cpa) = 1012 J/(kg K)
the thermal conductivity of brass (kb) = 111 W/(m K)
The traditional theory states that the galaxy formed
a. as a large spherical cloud of gas that was rotating very slowly. b. from a large cloud of material that broke off a larger galaxy. c. from material that had been ejected in the violent explosion of a dying galaxy. d. as a result of mergers between several smaller groups of gas, dust, and stars. e. as two massive galaxies collided.
An electron is sent at high speed toward a gold nucleus (charge +79e). What is the electrical force acting on the electron when it is 1.7 × 10^?14 m away from the gold nucleus? (e = 1.6 × 10^?19 C, ke = 8.99 × 10^9 N·m2/C2)
a. 6.3E+1 N b. 1.1E–12 N c. 5.0E+3 N d. 6.7E+6 N e. 8.0E–5 N
Aluminum alloys such as 2024 and 7050 _________ recommended for welding.
Fill in the blank(s) with the appropriate word(s).