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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Newton's rings illustrate
A) refraction. B) reflection. C) dispersion. D) polarization. E) interference.
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.