Ozone is a pollutant of city air caused by auto emissions. Therefore ozone is bad for Earth
a. True
b. False
Indicate whether the statement is true or false
False
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A heat exchanger wall consists of a copper plate 2 cm thick. The heat transfer coefficients on the two sides of the plate are 2700 and 7000 W/( m2 K), corresponding to fluid temperatures of 92 and 32°C, respectively. Assuming that the thermal conductivity of the wall is 375 W/ ( m K), (a) compute the surface temperatures in °C, and (b) calculate the heat flux in W/ m2.
GIVEN
• Heat exchanger wall, thickness (L) = 2 cm = 0.02 m
• Heat transfer coefficients
? hc1 = 2700 W/(m2 K)
? hc2 = 7000 W/(m2 K)
• Fluid temperatures
? Tf1 = 92°C
? Tf2 = 32°C
• Thermal conductivity of the wall (k) = 375 W/( m K) FIND (a) Surface temperatures (Tw1, Tw1) in °F (b) The heat flux (q/A) in W/m2. ASSUMPTIONS
• One dimensional heat transfer prevails
• The system has reached steady state
• Radiative heat transfer is negligible
SKETCH
A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with
A) 6 ohms. B) 6 amperes. C) 6 joules. D) 6 watts. E) 6 newtons.
Is it possible to transfer heat from a cold reservoir to a hot reservoir?
A) No. B) Yes; this will happen naturally. C) Yes, but work will have to be done. D) Theoretically yes, but it hasn't been accomplished yet.
Newton's rings illustrate
A) refraction. B) reflection. C) dispersion. D) polarization. E) interference.